Fine-grained 01420 Al-Li alloy sheets were produced by thermo-mechanical processing based on the mechanism of particle stimulated nucleation of recrystallization.The thermo-mechanically processed sheets were observed ...Fine-grained 01420 Al-Li alloy sheets were produced by thermo-mechanical processing based on the mechanism of particle stimulated nucleation of recrystallization.The thermo-mechanically processed sheets were observed to contain layers of different microstructures along the thickness.The precipitate behavior of the second phase particles and their effects on the distribution of dislocations and layered recrystallized grain structure were analyzed by optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray diffractometry(XRD).The formation mechanism of the gradient particles was discussed.The results show that after aging,a gradient distribution of large particles along the thickness is observed,the particles in the surface layer(SL) are distributed homogeneously,whereas those in the center layer(CL) are mainly distributed parallel to the rolling direction,and the volume fraction of the particles in the SL is higher than that in the CL.Subsequent rolling in the presence of layer-distributed particles results in a corresponding homogeneous distribution of highly strained regions in the SL and a banded distribution of them in CL,which is the main reason for the formation of layered grain structure along the thickness in the sheets.展开更多
The mining space of large mining height coal face is large,the range of movement and caving of rock strata is large and the stability of supports at coal face is low and damage rate of supports is high,which significa...The mining space of large mining height coal face is large,the range of movement and caving of rock strata is large and the stability of supports at coal face is low and damage rate of supports is high,which significantly affects the safe and efficient production of coal mines.By similar simulation experiment and theoretical analysis,the mode of fractured roofing structure of large mining height coal face and the method of determination of reasonable support resistance of the support was evaluated.Analysis shows that the structural mode of "combined cantilever beam – non-hinged roofing – hinged roofing" of the large mining height coal face appears at the roofing of large mining height coal face.The supporting factor of caved gangue at the gob is introduced,the calculating equations of the fractured step distance of roofing were derived and conventional calculating method of caved height of roofing was corrected and the method of determination of the length and height of each structural area of the roofing was provided.With reference to the excavating conditions at Jinhuagong coal mine in Datong minefield,the dimensions of structural areas of the roofing of the coal face were determined and analyzed,and reasonable support resistance of the height coal face was acquired.By selecting Model ZZ13000/28/60 support and with procedures of advanced pre-cracking blasting,the safe production of large mining height coal face was assured.展开更多
基金Project(2006DFA53250) supported by the International Science and Technology Cooperation Program of ChinaProject(2005CB623706) supported by the Major State Basic Research Development Program of China
文摘Fine-grained 01420 Al-Li alloy sheets were produced by thermo-mechanical processing based on the mechanism of particle stimulated nucleation of recrystallization.The thermo-mechanically processed sheets were observed to contain layers of different microstructures along the thickness.The precipitate behavior of the second phase particles and their effects on the distribution of dislocations and layered recrystallized grain structure were analyzed by optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray diffractometry(XRD).The formation mechanism of the gradient particles was discussed.The results show that after aging,a gradient distribution of large particles along the thickness is observed,the particles in the surface layer(SL) are distributed homogeneously,whereas those in the center layer(CL) are mainly distributed parallel to the rolling direction,and the volume fraction of the particles in the SL is higher than that in the CL.Subsequent rolling in the presence of layer-distributed particles results in a corresponding homogeneous distribution of highly strained regions in the SL and a banded distribution of them in CL,which is the main reason for the formation of layered grain structure along the thickness in the sheets.
基金Project(51174192)supported by the National Natural Science Foundation of ChinaProject(BRA2010024)supported by "333" Training Foundation of Jiangsu Province,China+2 种基金Projects(2011QNB03,2014ZDPY21,2014QNB30)supported by the Fundamental Research Funds for the Central Universities,ChinaProject Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,ChinaProject(2015M581896)supported by China Postdoctoral Science Foundation
文摘The mining space of large mining height coal face is large,the range of movement and caving of rock strata is large and the stability of supports at coal face is low and damage rate of supports is high,which significantly affects the safe and efficient production of coal mines.By similar simulation experiment and theoretical analysis,the mode of fractured roofing structure of large mining height coal face and the method of determination of reasonable support resistance of the support was evaluated.Analysis shows that the structural mode of "combined cantilever beam – non-hinged roofing – hinged roofing" of the large mining height coal face appears at the roofing of large mining height coal face.The supporting factor of caved gangue at the gob is introduced,the calculating equations of the fractured step distance of roofing were derived and conventional calculating method of caved height of roofing was corrected and the method of determination of the length and height of each structural area of the roofing was provided.With reference to the excavating conditions at Jinhuagong coal mine in Datong minefield,the dimensions of structural areas of the roofing of the coal face were determined and analyzed,and reasonable support resistance of the height coal face was acquired.By selecting Model ZZ13000/28/60 support and with procedures of advanced pre-cracking blasting,the safe production of large mining height coal face was assured.
