An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS...An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.展开更多
Al-Cu-Mg-Ag alloys have become a research hotspot because of its good heat resistance.Its excellent mechanical properties are inseparable from the regulation of the structure by researchers.The method of material stru...Al-Cu-Mg-Ag alloys have become a research hotspot because of its good heat resistance.Its excellent mechanical properties are inseparable from the regulation of the structure by researchers.The method of material structure simulation has become more and more perfect.This study employs numerical simulation to investigate the microstructure evolution of Al-Cu-Mg-Ag alloys during solidification with the aim of controlling its structure.The size distribution of Ti-containing particles in an Al-Ti-B master alloy was characterized via microstructure observation,serving as a basis for optimizing the nucleation density parameters for particles of varying radii in the phase field model.The addition of refiner inhibited the growth of dendrites and no longer produced coarse dendrites.With the increase of refiner,the grains gradually tended to form cellular morphology.The refined grains were about 100μm in size.Experimental validation of the simulated as-cast grain morphology was conducted.The samples were observed by metallographic microscope and scanning electron microscope.The addition of refiner had a significant effect on the refinement of the alloy,and the average grain size after refinement was also about 100μm.At the same time,the XRD phase identification of the alloy was carried out.The observation of the microstructure morphology under the scanning electron microscope showed that the precipitated phase was mainly concentrated on the grain boundary.The Al_(2)Cu accounted for about 5%,and the matrix phase FCC accounted for about 95%,which also corresponded well with the simulation results.展开更多
China is extremely poor in mineral resources of Platinum Group Metals (PGMs), productive output of PGMs from mineral resource is 2.5 tons per year. At the same time, China is the biggest PGMs consumption country in th...China is extremely poor in mineral resources of Platinum Group Metals (PGMs), productive output of PGMs from mineral resource is 2.5 tons per year. At the same time, China is the biggest PGMs consumption country in the world, the mineral resource of PGMs is critical shortage, it shows the importance of recycling the secondary resource of PGMs. Sino-Platinum Metals Resource (Yimen) Co., Ltd. is the leader in recycling of PGMs from secondary resource, and has made outstanding contributions to China PGMs secondary resources recycling. This article elucidates the current situation of secondary resources recovery and development of metallurgical technology for PGMs.展开更多
The experiment of ultrasonic treatment of roll casting aluminum strip on plane twin-roll cast-roller with double-heads ultrasonic tools was carried out, and the metallographic structure of the roll casting aluminum st...The experiment of ultrasonic treatment of roll casting aluminum strip on plane twin-roll cast-roller with double-heads ultrasonic tools was carried out, and the metallographic structure of the roll casting aluminum strip treated by ultrasonic was studied. The results show that ultrasonic treatment can refine the grain of the roll casting aluminum strips and make the structure of the strips more homogeneous. The effect is the best when the power of ultrasonic is 300 W and the incident angle of the guide rod is 45、. The mechanism of acoustic cavitations and acoustic flow on grain refinement was also discussed. The heat effect of intensity ultrasonic was studied. The present problems during ultrasonic roll casting process, such as the imperfect cooling system, the inaccurate calculation of ultrasonic energy, and the shape and position of the guide rod to be improved were pointed out.展开更多
Combining refined composite multiscale fuzzy entropy(RCMFE)and support vector machine(SVM)with particle swarm optimization(PSO)for diagnosing roller bearing faults is proposed in this paper.Compared with refined compo...Combining refined composite multiscale fuzzy entropy(RCMFE)and support vector machine(SVM)with particle swarm optimization(PSO)for diagnosing roller bearing faults is proposed in this paper.Compared with refined composite multiscale sample entropy(RCMSE)and multiscale fuzzy entropy(MFE),the smoothness of RCMFE is superior to that of those models.The corresponding comparison of smoothness and analysis of validity through decomposition accuracy are considered in the numerical experiments by considering the white and 1/f noise signals.Then RCMFE,RCMSE and MFE are developed to affect extraction by using different roller bearing vibration signals.Then the extracted RCMFE,RCMSE and MFE eigenvectors are regarded as the input of the PSO-SVM to diagnose the roller bearing fault.Finally,the results show that the smoothness of RCMFE is superior to that of RCMSE and MFE.Meanwhile,the fault classification accuracy is higher than that of RCMSE and MFE.展开更多
In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The...In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The hollow-roll model has equivalent stiffness of bending resistance and deformation to the real solid and much less meshes,so the computational time is greatly reduced.Based on these,the factors influencing plate profile,such as the roll-bending force,initial crown,thermal crown and heat transfer during rolling and inter-pass cooling can be taken into account in the simulation.The auto mesh-refining module with data passing can automatically refine and re-number elements and transfer the nodal and elemental results to the new meshes.Furthermore,the 3-D modeling routine is parametrically developed and can be run independently of Marc pre-processing program.A seven-pass industrial hot rolling process was continuously simulated to validate the accuracy of model.By comparison of the calculated results with the industrial measured data,the rolling force,temperature and plate profile are in good accordance with the measured ones.展开更多
A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting h...A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting high nickel matte trapping-aluminothermic activation method to recovery rhodium from incinerator residue of organic rhodium waste. The method is shorter process, lower equipment requirement, and the higher activity of rhodium black. In pyrometallurgy enrichment process,the recovery rate of rhodium reached 94.65%, the full flow of rhodium recovery rate was 92.04%.展开更多
The effect of an ultrasonic field on the microstructure and mechanical properties of 7085 aluminum alloy during solidification was investigated by optical microscopy, Vickers hardness test, tensile test, scanning elec...The effect of an ultrasonic field on the microstructure and mechanical properties of 7085 aluminum alloy during solidification was investigated by optical microscopy, Vickers hardness test, tensile test, scanning electron microscopy （SEM） with energy dispersive X-ray spectrometry, and electron probe micro-analysis （EPMA）. The results showed that the grains of aluminum alloy were significantly refined and secondary phases were dispersed and distributed uniformly at the grain boundaries, due to ultrasonic treatment （UST）. By EPMA, it was observed that the distribution of the main elements A1, Zn, Mg and Cu was more homogeneous in alloys with UST, than in alloys without UST. The mechanical properties of the aluminum alloy also significantly improved. As demonstrated by the SEM fractography of the fractured faces of several castings, fracture of the unrefined specimens occurred in a brittle manner, whereas the cracks of the refined specimens showed quasi-cleavage fracture.展开更多
High purity （99.999% or 5N, mass fraction） indium （In） was obtained through vacuum distillation using a 2N （99%） In as input material under a dynamic vacuum of 5 Pa. The glow discharge mass spectrometry （GDMS）...High purity （99.999% or 5N, mass fraction） indium （In） was obtained through vacuum distillation using a 2N （99%） In as input material under a dynamic vacuum of 5 Pa. The glow discharge mass spectrometry （GDMS） was applied for the analysis of input material and the distilled indium. The results indicate that high-volatile impurities namely Cd, Zn, T1 and Pb can be removed from the indium matrix at the low fraction stage of 1 223 K for 120 min; Low-volatile impurities such as Fe, Ni, Cu, Sn can be reduced at the high fraction stage of 1 323 K for 120 min. The separation coefficient ,8i and activity coefficient Yi of impurities are calculated according to the experiments to fill the inadequate data of the thermodynamics.展开更多
The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1...The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.展开更多
An embedded cryptosystem needs higher reconfiguration capability and security. After analyzing the newly emerging side-channel attacks on elliptic curve cryptosystem （ECC）, an efficient fractional width-w NAF （FWNA...An embedded cryptosystem needs higher reconfiguration capability and security. After analyzing the newly emerging side-channel attacks on elliptic curve cryptosystem （ECC）, an efficient fractional width-w NAF （FWNAF） algorithm is proposed to secure ECC scalar multiplication from these attacks. This algorithm adopts the fractional window method and probabilistic SPA scheme to reconfigure the pre-computed table, and it allows designers to make a dynamic configuration on pre-computed table. And then, it is enhanced to resist SPA, DPA, RPA and ZPA attacks by using the random masking method. Compared with the WBRIP and EBRIP methods, our proposals has the lowest total computation cost and reduce the shake phenomenon due to sharp fluctuation on computation performance.展开更多
The behaviors of the precipitation and decomposition of carbides in AISI M2 high-speed steel modified by nitrogen and mischmetal were investigated using DSC, XRD, SEM and TEM. The as-cast microstructure of the experim...The behaviors of the precipitation and decomposition of carbides in AISI M2 high-speed steel modified by nitrogen and mischmetal were investigated using DSC, XRD, SEM and TEM. The as-cast microstructure of the experimental steel consists of dendrites of iron matrix, networks of eutectic carbides and secondary carbides. The average distance between networks is about 34 μm. The carbides mainly include M_2C, M(C,N) and M_6C, and their relative contents are 58.5%, 30.3% and 11.2%, respectively. The average spacing between the M_2C fibers is 1.5 μm. The decomposition of M_2C occurs from 897.2 to 1221.5 ℃(heating rate of 200 ℃/h). Some precipitated carbide particles occur in the M_2C matrix after holding for 15 min at 1100 ℃. With increasing holding time, the carbide fibers neck down more and more obviously until they are broken down. The spectral peaks of M_2C almost disappear after holding for 60 min. The spectral peaks of M_6C gradually strengthen with the holding time, and the relative content of M_6C increases to 79.8% after holding for 60 min. After holding for 180 min, the carbide fibers disappear, and the decomposition products consist of fine carbide particles(about 300 nm) and short rod-like carbides(about 3.5 μm).展开更多
For anomaly detection,anomalies existing in the background will affect the detection performance.Accordingly,a background refinement method based on the local density is proposed to remove the anomalies from thebackgr...For anomaly detection,anomalies existing in the background will affect the detection performance.Accordingly,a background refinement method based on the local density is proposed to remove the anomalies from thebackground.In this work,the local density is measured by its spectral neighbors through a certain radius which is obtained by calculating the mean median of the distance matrix.Further,a two-step segmentation strategy is designed.The first segmentation step divides the original background into two subsets,a large subset composed by background pixels and a small subset containing both background pixels and anomalies.The second segmentation step employing Otsu method with an aim to obtain a discrimination threshold is conducted on the small subset.Then the pixels whose local densities are lower than the threshold are removed.Finally,to validate the effectiveness of the proposed method,it combines Reed-Xiaoli detector and collaborative-representation-based detector to detect anomalies.Experiments are conducted on two real hyperspectral datasets.Results show that the proposed method achieves better detection performance.展开更多
Effect of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy was investigated. The results show that electromagnetic stirring causes a change of morphology of α-Mg phase from coarse dendrites t...Effect of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy was investigated. The results show that electromagnetic stirring causes a change of morphology of α-Mg phase from coarse dendrites to fine rosette-like or spherical shape. Grain size is significantly refined within the range of input voltage 75?125 V, moreover, the optimum input voltage corresponded to the minimum value (64 μm) of grain size is 125 V. Compared to the non-stirred condition, the amount of β-Mg17Al12 precipitate under the stirred condition obviously increases. The grain refinement of AZ91-0.8%Ce alloy is mainly attributed to multiplication of existing grains in the melt caused by forced fluid flow under electromagnetic stirring condition. Addition of 0.8% Ce results in the formation of ‘necking’ at secondary dendrite arm roots of α-Mg crystals, and consequently, it is helpful to increase the number of heterogeneous nucleation.展开更多
In order to prolong the service life of aircraft skin made from AA2524, the effects of laser shock peening(LSP) on fatigue crack growth(FCG) rate and fracture toughness(K_(c)) of AA2524 were investigated. Multiple LSP...In order to prolong the service life of aircraft skin made from AA2524, the effects of laser shock peening(LSP) on fatigue crack growth(FCG) rate and fracture toughness(K_(c)) of AA2524 were investigated. Multiple LSP treatment was performed on compact tension(CT) specimen from single side and double sides. The surface integrity was measured with Vickers hardness tester, X-ray diffractometer and confocal laser scanning microscope, respectively. FCG rate test and fracture toughness test under plane stress were carried out after LSP treatment. The microstructure features of cross-sections were observed with scanning electron microscope. The results showed that the micro-hardness and residual stress of CT specimens were increased dramatically after LSP treatment. Compared to the base metal(BM), the fatigue life was prolonged by 2.4 times and fracture toughness was increased by 22% after multiple LSP.展开更多
In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cas...In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.展开更多
基金Project(51174177)supported by the National Natural Science Foundation of China
文摘An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.
文摘Al-Cu-Mg-Ag alloys have become a research hotspot because of its good heat resistance.Its excellent mechanical properties are inseparable from the regulation of the structure by researchers.The method of material structure simulation has become more and more perfect.This study employs numerical simulation to investigate the microstructure evolution of Al-Cu-Mg-Ag alloys during solidification with the aim of controlling its structure.The size distribution of Ti-containing particles in an Al-Ti-B master alloy was characterized via microstructure observation,serving as a basis for optimizing the nucleation density parameters for particles of varying radii in the phase field model.The addition of refiner inhibited the growth of dendrites and no longer produced coarse dendrites.With the increase of refiner,the grains gradually tended to form cellular morphology.The refined grains were about 100μm in size.Experimental validation of the simulated as-cast grain morphology was conducted.The samples were observed by metallographic microscope and scanning electron microscope.The addition of refiner had a significant effect on the refinement of the alloy,and the average grain size after refinement was also about 100μm.At the same time,the XRD phase identification of the alloy was carried out.The observation of the microstructure morphology under the scanning electron microscope showed that the precipitated phase was mainly concentrated on the grain boundary.The Al_(2)Cu accounted for about 5%,and the matrix phase FCC accounted for about 95%,which also corresponded well with the simulation results.
基金the National High Technology Research and Development Program of China(863 Program) (2012AA063203)Funded by Science and Technology Department of Yunnan Province (2011AA004)
文摘China is extremely poor in mineral resources of Platinum Group Metals (PGMs), productive output of PGMs from mineral resource is 2.5 tons per year. At the same time, China is the biggest PGMs consumption country in the world, the mineral resource of PGMs is critical shortage, it shows the importance of recycling the secondary resource of PGMs. Sino-Platinum Metals Resource (Yimen) Co., Ltd. is the leader in recycling of PGMs from secondary resource, and has made outstanding contributions to China PGMs secondary resources recycling. This article elucidates the current situation of secondary resources recovery and development of metallurgical technology for PGMs.
基金Projects(IRT0549) supported by Program for Changjiang Scholars and Innovative Research Team in University, China
文摘The experiment of ultrasonic treatment of roll casting aluminum strip on plane twin-roll cast-roller with double-heads ultrasonic tools was carried out, and the metallographic structure of the roll casting aluminum strip treated by ultrasonic was studied. The results show that ultrasonic treatment can refine the grain of the roll casting aluminum strips and make the structure of the strips more homogeneous. The effect is the best when the power of ultrasonic is 300 W and the incident angle of the guide rod is 45、. The mechanism of acoustic cavitations and acoustic flow on grain refinement was also discussed. The heat effect of intensity ultrasonic was studied. The present problems during ultrasonic roll casting process, such as the imperfect cooling system, the inaccurate calculation of ultrasonic energy, and the shape and position of the guide rod to be improved were pointed out.
基金Projects(City U 11201315,T32-101/15-R)supported by the Research Grants Council of the Hong Kong Special Administrative Region,China
文摘Combining refined composite multiscale fuzzy entropy(RCMFE)and support vector machine(SVM)with particle swarm optimization(PSO)for diagnosing roller bearing faults is proposed in this paper.Compared with refined composite multiscale sample entropy(RCMSE)and multiscale fuzzy entropy(MFE),the smoothness of RCMFE is superior to that of those models.The corresponding comparison of smoothness and analysis of validity through decomposition accuracy are considered in the numerical experiments by considering the white and 1/f noise signals.Then RCMFE,RCMSE and MFE are developed to affect extraction by using different roller bearing vibration signals.Then the extracted RCMFE,RCMSE and MFE eigenvectors are regarded as the input of the PSO-SVM to diagnose the roller bearing fault.Finally,the results show that the smoothness of RCMFE is superior to that of RCMSE and MFE.Meanwhile,the fault classification accuracy is higher than that of RCMSE and MFE.
基金Project(20050248007) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘In order to continuously simulate multi-pass plate rolling process,a 3-D elastic hollow-roll model was proposed and an auto mesh-refining module with data passing was developed and integrated with FE software,Marc.The hollow-roll model has equivalent stiffness of bending resistance and deformation to the real solid and much less meshes,so the computational time is greatly reduced.Based on these,the factors influencing plate profile,such as the roll-bending force,initial crown,thermal crown and heat transfer during rolling and inter-pass cooling can be taken into account in the simulation.The auto mesh-refining module with data passing can automatically refine and re-number elements and transfer the nodal and elemental results to the new meshes.Furthermore,the 3-D modeling routine is parametrically developed and can be run independently of Marc pre-processing program.A seven-pass industrial hot rolling process was continuously simulated to validate the accuracy of model.By comparison of the calculated results with the industrial measured data,the rolling force,temperature and plate profile are in good accordance with the measured ones.
基金the National High Technology Research and Development Program of China(863 Program): (2012AA063203, 2012AA063204, 2012AA063207)
文摘A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting high nickel matte trapping-aluminothermic activation method to recovery rhodium from incinerator residue of organic rhodium waste. The method is shorter process, lower equipment requirement, and the higher activity of rhodium black. In pyrometallurgy enrichment process,the recovery rate of rhodium reached 94.65%, the full flow of rhodium recovery rate was 92.04%.
基金Project(2016GK1004)supported by the Science and Technology Major Project of Hunan Province,China
文摘The effect of an ultrasonic field on the microstructure and mechanical properties of 7085 aluminum alloy during solidification was investigated by optical microscopy, Vickers hardness test, tensile test, scanning electron microscopy （SEM） with energy dispersive X-ray spectrometry, and electron probe micro-analysis （EPMA）. The results showed that the grains of aluminum alloy were significantly refined and secondary phases were dispersed and distributed uniformly at the grain boundaries, due to ultrasonic treatment （UST）. By EPMA, it was observed that the distribution of the main elements A1, Zn, Mg and Cu was more homogeneous in alloys with UST, than in alloys without UST. The mechanical properties of the aluminum alloy also significantly improved. As demonstrated by the SEM fractography of the fractured faces of several castings, fracture of the unrefined specimens occurred in a brittle manner, whereas the cracks of the refined specimens showed quasi-cleavage fracture.
基金Project(2009AA003) supported by Science and Technology Innovation Plan of Yunnan Province, China
文摘High purity （99.999% or 5N, mass fraction） indium （In） was obtained through vacuum distillation using a 2N （99%） In as input material under a dynamic vacuum of 5 Pa. The glow discharge mass spectrometry （GDMS） was applied for the analysis of input material and the distilled indium. The results indicate that high-volatile impurities namely Cd, Zn, T1 and Pb can be removed from the indium matrix at the low fraction stage of 1 223 K for 120 min; Low-volatile impurities such as Fe, Ni, Cu, Sn can be reduced at the high fraction stage of 1 323 K for 120 min. The separation coefficient ,8i and activity coefficient Yi of impurities are calculated according to the experiments to fill the inadequate data of the thermodynamics.
基金Project(2012AA03A503) supported by the National High Technology Research and Development Program of China
文摘The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.
基金supported by the National Natural Science Foundation of China(60373109)Ministry of Science and Technologyof China and the National Commercial Cryptography Application Technology Architecture and Application DemonstrationProject(2008BAA22B02).
文摘An embedded cryptosystem needs higher reconfiguration capability and security. After analyzing the newly emerging side-channel attacks on elliptic curve cryptosystem （ECC）, an efficient fractional width-w NAF （FWNAF） algorithm is proposed to secure ECC scalar multiplication from these attacks. This algorithm adopts the fractional window method and probabilistic SPA scheme to reconfigure the pre-computed table, and it allows designers to make a dynamic configuration on pre-computed table. And then, it is enhanced to resist SPA, DPA, RPA and ZPA attacks by using the random masking method. Compared with the WBRIP and EBRIP methods, our proposals has the lowest total computation cost and reduce the shake phenomenon due to sharp fluctuation on computation performance.
基金Project(E2016203256)supported by the Natural Science Foundation of Hebei Province,China
文摘The behaviors of the precipitation and decomposition of carbides in AISI M2 high-speed steel modified by nitrogen and mischmetal were investigated using DSC, XRD, SEM and TEM. The as-cast microstructure of the experimental steel consists of dendrites of iron matrix, networks of eutectic carbides and secondary carbides. The average distance between networks is about 34 μm. The carbides mainly include M_2C, M(C,N) and M_6C, and their relative contents are 58.5%, 30.3% and 11.2%, respectively. The average spacing between the M_2C fibers is 1.5 μm. The decomposition of M_2C occurs from 897.2 to 1221.5 ℃(heating rate of 200 ℃/h). Some precipitated carbide particles occur in the M_2C matrix after holding for 15 min at 1100 ℃. With increasing holding time, the carbide fibers neck down more and more obviously until they are broken down. The spectral peaks of M_2C almost disappear after holding for 60 min. The spectral peaks of M_6C gradually strengthen with the holding time, and the relative content of M_6C increases to 79.8% after holding for 60 min. After holding for 180 min, the carbide fibers disappear, and the decomposition products consist of fine carbide particles(about 300 nm) and short rod-like carbides(about 3.5 μm).
基金Projects(61405041,61571145)supported by the National Natural Science Foundation of ChinaProject(ZD201216)supported by the Key Program of Heilongjiang Natural Science Foundation,China+1 种基金Project(RC2013XK009003)supported by Program Excellent Academic Leaders of Harbin,ChinaProject(HEUCF1508)supported by the Fundamental Research Funds for the Central Universities,China
文摘For anomaly detection,anomalies existing in the background will affect the detection performance.Accordingly,a background refinement method based on the local density is proposed to remove the anomalies from thebackground.In this work,the local density is measured by its spectral neighbors through a certain radius which is obtained by calculating the mean median of the distance matrix.Further,a two-step segmentation strategy is designed.The first segmentation step divides the original background into two subsets,a large subset composed by background pixels and a small subset containing both background pixels and anomalies.The second segmentation step employing Otsu method with an aim to obtain a discrimination threshold is conducted on the small subset.Then the pixels whose local densities are lower than the threshold are removed.Finally,to validate the effectiveness of the proposed method,it combines Reed-Xiaoli detector and collaborative-representation-based detector to detect anomalies.Experiments are conducted on two real hyperspectral datasets.Results show that the proposed method achieves better detection performance.
基金Project(2004ABA110) supported by the Natural Science Foundation of Hubei Province project(471-38300843) supported by the Research Foundation for the Doctoral Program of Wuhan University of Technology
文摘Effect of electromagnetic stirring on microstructure of AZ91-0.8%Ce magnesium alloy was investigated. The results show that electromagnetic stirring causes a change of morphology of α-Mg phase from coarse dendrites to fine rosette-like or spherical shape. Grain size is significantly refined within the range of input voltage 75?125 V, moreover, the optimum input voltage corresponded to the minimum value (64 μm) of grain size is 125 V. Compared to the non-stirred condition, the amount of β-Mg17Al12 precipitate under the stirred condition obviously increases. The grain refinement of AZ91-0.8%Ce alloy is mainly attributed to multiplication of existing grains in the melt caused by forced fluid flow under electromagnetic stirring condition. Addition of 0.8% Ce results in the formation of ‘necking’ at secondary dendrite arm roots of α-Mg crystals, and consequently, it is helpful to increase the number of heterogeneous nucleation.
基金Project(52075552) supported by the National Natural Science Foundation of ChinaProject(kq2007085) supported by Changsha Municipal Natural Science Foundation,China。
文摘In order to prolong the service life of aircraft skin made from AA2524, the effects of laser shock peening(LSP) on fatigue crack growth(FCG) rate and fracture toughness(K_(c)) of AA2524 were investigated. Multiple LSP treatment was performed on compact tension(CT) specimen from single side and double sides. The surface integrity was measured with Vickers hardness tester, X-ray diffractometer and confocal laser scanning microscope, respectively. FCG rate test and fracture toughness test under plane stress were carried out after LSP treatment. The microstructure features of cross-sections were observed with scanning electron microscope. The results showed that the micro-hardness and residual stress of CT specimens were increased dramatically after LSP treatment. Compared to the base metal(BM), the fatigue life was prolonged by 2.4 times and fracture toughness was increased by 22% after multiple LSP.
基金Projects(2020YFB0311400ZL, 2020YFF0218202) supported by the National Key R&D Program of ChinaProject supported by Youth Fund Project of GRINM Group Co.,Ltd.,China。
文摘In the present work, scandium elements with a series of contents(0.06 wt.%, 0.10 wt.%, 0.14 wt.%,0.17 wt.%, 0.20 wt.% and 0.25 wt.%) were added in a high Zn-containing Al-Zn-Mg-Cu-Zr alloy and the corresponding as-cast microstructure characteristics including grains and phases were thoroughly investigated. The results indicated that fine grain boundaries existed in these alloys and fine MgZn2phases discontinuously distributed on them. Besides,AlZnMgCu eutectic phases and Sc, Zr-containing phases with flocculent morphology were observed. As scandium contents vary from 0.06 wt.% to 0.17 wt.%, the average grain size continuously decreased and its equiaxial characteristics were strengthened. Meanwhile, the content of AlZnMgCu eutectic phase showed a decrease trend. When scandium contents were 0.20 wt.% and 0.25 wt.%, no further enhancement on grain refinement was observed, so as to the reduction of AlZnMgCu eutectic phase content. Besides, Sc, Zr-containing phases with blocky morphology were observed and the alloy with a scandium content of 0.25 wt.% possessed a larger amount of blocky Sc, Zr-containing phase than the alloy with a scandium content of 0.20 wt.%. Grain refinement and reduction of AlZnMgCu eutectic phase content associated with scandium addition were discussed.
