The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering.At elevated temperatures,oxidation of the surfaces h...The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering.At elevated temperatures,oxidation of the surfaces has an effective role in the fatigue strength and ductility of the alloys.In the present work,the effect of prior cyclic oxidation on the high temperature low cycle fatigue(HTLCF)properties of nickel-based superalloy Rene®80 has been assessed in the uncoated state and in the Pt-aluminide(Pt-Al)coated condition at 930℃.To apply cyclic oxidation,simulation of engine thermal exposure was carried out by exposing coated and uncoated fatigue specimens in the burner rig(120 cycles at 1100℃).The cyclic oxidation procedure led to a changing in the coating microstructure from the dual-phase(ξ-PtAl_(2)+β-(Ni,Pt)Al)to single phase(β-(Ni,Pt)Al).Results of HTLCF tests showed an improvement in the HTLCF life around 11.5%in the unexposed coated specimen(pre-cyclic oxidation)as compared to unexposed bare specimen,while this rise for exposed coated specimen(post-cyclic oxidation)was only 5%.Although a mixed mode fracture morphology(ductile and brittle)was observed on the fracture surfaces of failed specimens,the wider regions of brittle fracture belonged to exposed coated/uncoated ones.展开更多
A study on the low-cycle fatigue(LCF)behavior of K 416 B alloy was conducted at 650℃.According to the results,the LCF behavior of K 416 B alloy at 650℃ is mainly manifested as elastic deformation and the fatigue lif...A study on the low-cycle fatigue(LCF)behavior of K 416 B alloy was conducted at 650℃.According to the results,the LCF behavior of K 416 B alloy at 650℃ is mainly manifested as elastic deformation and the fatigue life of the alloy is determined by the level of material strength.When tension-compression fatigue occurs,the deformation mechanism of the alloy is reflected in the form of dislocation slip,and the deformation dislocations are bowed out in the matrix by Orowan mechanism,which leads to a dislocation configuration similar to the Frawk-Reed source.At the late stage of low-cycle fatigue,the fatigue-induced cracks develop from the alloy surface.As fatigue test proceeds,it is possible for the cracks to continue development along the regions of eutectic and the bulk M 6 C carbide due to stress concentration,thus causing the alloy to show cleavage fracture.展开更多
The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy w...The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy were obtained by using a miniature tester that combined the functions of in situ tensile and fatigue testing. A piezoelectric actuator was adopted as the actuator for the fatigue testing, and the feasibility of the fatigue actuator was verified by the transient harmonic response analysis based on static tensile preload and dynamic sinusoidal load. The experimental results show that the yield strength and tensile strength of the C11000 copper are improved after adding 37%(mass fraction) zinc, and H63 copper-zinc alloy presents more obvious cyclic hardening behavior and more consumed irreversible plastic work during each stress cycle compared with C11000 copper for the same strain controlled cycling. Additionally, based on the Manson-Coffin theory, the strain-life equations of the two materials were also obtained. C11000 copper and H63 copper-zinc alloy show transition life of 16832 and 1788 cycles, respectively.展开更多
文摘The prediction of fatigue life of metallic alloys is justly accepted as one of the most important phenomena in the field of metallurgical and mechanical engineering.At elevated temperatures,oxidation of the surfaces has an effective role in the fatigue strength and ductility of the alloys.In the present work,the effect of prior cyclic oxidation on the high temperature low cycle fatigue(HTLCF)properties of nickel-based superalloy Rene®80 has been assessed in the uncoated state and in the Pt-aluminide(Pt-Al)coated condition at 930℃.To apply cyclic oxidation,simulation of engine thermal exposure was carried out by exposing coated and uncoated fatigue specimens in the burner rig(120 cycles at 1100℃).The cyclic oxidation procedure led to a changing in the coating microstructure from the dual-phase(ξ-PtAl_(2)+β-(Ni,Pt)Al)to single phase(β-(Ni,Pt)Al).Results of HTLCF tests showed an improvement in the HTLCF life around 11.5%in the unexposed coated specimen(pre-cyclic oxidation)as compared to unexposed bare specimen,while this rise for exposed coated specimen(post-cyclic oxidation)was only 5%.Although a mixed mode fracture morphology(ductile and brittle)was observed on the fracture surfaces of failed specimens,the wider regions of brittle fracture belonged to exposed coated/uncoated ones.
基金Projects(51701212,51771191,51971214)supported by the National Natural Science Foundation of ChinaProject(2019-MS-336)supported by the Liaoning Provincial Natural Science Foundation,China。
文摘A study on the low-cycle fatigue(LCF)behavior of K 416 B alloy was conducted at 650℃.According to the results,the LCF behavior of K 416 B alloy at 650℃ is mainly manifested as elastic deformation and the fatigue life of the alloy is determined by the level of material strength.When tension-compression fatigue occurs,the deformation mechanism of the alloy is reflected in the form of dislocation slip,and the deformation dislocations are bowed out in the matrix by Orowan mechanism,which leads to a dislocation configuration similar to the Frawk-Reed source.At the late stage of low-cycle fatigue,the fatigue-induced cracks develop from the alloy surface.As fatigue test proceeds,it is possible for the cracks to continue development along the regions of eutectic and the bulk M 6 C carbide due to stress concentration,thus causing the alloy to show cleavage fracture.
基金Projects(51275198,51422503)supported by the National Natural Science Foundation of ChinaProject(2012YQ030075)supported by Special Funds for Development of National Major Scientific Instruments and Equipments,China+1 种基金Project(NECT-12-0238)supported by Program for New Century Excellent Talents in University,ChinaProject(20150520108JH)supported by Young Scientist Fund of Jilin Province of China
文摘The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy were obtained by using a miniature tester that combined the functions of in situ tensile and fatigue testing. A piezoelectric actuator was adopted as the actuator for the fatigue testing, and the feasibility of the fatigue actuator was verified by the transient harmonic response analysis based on static tensile preload and dynamic sinusoidal load. The experimental results show that the yield strength and tensile strength of the C11000 copper are improved after adding 37%(mass fraction) zinc, and H63 copper-zinc alloy presents more obvious cyclic hardening behavior and more consumed irreversible plastic work during each stress cycle compared with C11000 copper for the same strain controlled cycling. Additionally, based on the Manson-Coffin theory, the strain-life equations of the two materials were also obtained. C11000 copper and H63 copper-zinc alloy show transition life of 16832 and 1788 cycles, respectively.
