The flow stress behaviors of squeeze casting SiCp/2A50 matrix composites were investigated by means of compression tests on a Gleeble 1500 therma1 mechanical simulator at isothermal constant strain rates ranging from ...The flow stress behaviors of squeeze casting SiCp/2A50 matrix composites were investigated by means of compression tests on a Gleeble 1500 therma1 mechanical simulator at isothermal constant strain rates ranging from of 0.001 to 1.0 with the testing temperature ranging from 350 to 500 ℃. The experiments showed that the relationship between stress and strain was obviously influenced by the strain rate and temperature. Dynamic recrystallization generally occurred at a higher temperature and a 1ower strain rate. A linear equation could be fitted between the Zener-Hollomon parameter Z and stress in the experiments. The mean value reciprocal of temperature at every true strain had a linear relation with natural logarithm of Z parameter, and the correlation coefficient, R=0.99, which was very significant by examination. The hot deformation activation energy of SiCp/2A50 matrix composites was 163.47 KJ/mol by calculation.展开更多
A coarse-grained AM50 alloy was used as a model alloy for investigation of constitutive behaviour,Charpy toughness and effect of stress state on deformation and failure of cast Mg alloys.The results provide critical m...A coarse-grained AM50 alloy was used as a model alloy for investigation of constitutive behaviour,Charpy toughness and effect of stress state on deformation and failure of cast Mg alloys.The results provide critical mechanical properties of a cast AM50 alloy for crashworthiness assessment and development of finite element simulation techniques.For cast Mg alloys,the effect of strain rate and temperature is larger on tensile strength than on compressive strength because twinning is more extensive in compression than in tension.The effect of strain rate on compressive strength is negligible because twinning activity of the cast Mg alloy is dominant.The load vs.deflection of Charpy specimens were measured for modelling,and the effect of loading rate and temperature on load of Charpy specimens is very small because part of the specimen is in compression.The equivalent strain to fracture of the cylindrical round notched tension specimen decreases with increasing stress triaxiality;though for the flat-grooved plane strain specimen,the equivalent fracture strain remains constant over the range of stress triaxiality investigated.Because the two different specimen geometries give rise to different Lode angle values,the test results show that the Lode angle parameter is an important parameter for deformation and fracture of Mg alloys.Finite element simulations of loading of the cylindrical notched-tension and Charpy specimens were carried out using a Lode-angle dependent von Mises model,and were found to provide a reasonable description of the load-displacement curves measured in the tests.For the flat-grooved plane strain specimens,the computations under-predicted the force-displacement response measured.展开更多
文摘The flow stress behaviors of squeeze casting SiCp/2A50 matrix composites were investigated by means of compression tests on a Gleeble 1500 therma1 mechanical simulator at isothermal constant strain rates ranging from of 0.001 to 1.0 with the testing temperature ranging from 350 to 500 ℃. The experiments showed that the relationship between stress and strain was obviously influenced by the strain rate and temperature. Dynamic recrystallization generally occurred at a higher temperature and a 1ower strain rate. A linear equation could be fitted between the Zener-Hollomon parameter Z and stress in the experiments. The mean value reciprocal of temperature at every true strain had a linear relation with natural logarithm of Z parameter, and the correlation coefficient, R=0.99, which was very significant by examination. The hot deformation activation energy of SiCp/2A50 matrix composites was 163.47 KJ/mol by calculation.
基金This study is part of CanmetMATERIALS(CMAT)projects funded by the Magnesium Front End R&D(MFERD)program provided by Natural Resources Canada through the Program of Energy Research and Development and Transport Canada.
文摘A coarse-grained AM50 alloy was used as a model alloy for investigation of constitutive behaviour,Charpy toughness and effect of stress state on deformation and failure of cast Mg alloys.The results provide critical mechanical properties of a cast AM50 alloy for crashworthiness assessment and development of finite element simulation techniques.For cast Mg alloys,the effect of strain rate and temperature is larger on tensile strength than on compressive strength because twinning is more extensive in compression than in tension.The effect of strain rate on compressive strength is negligible because twinning activity of the cast Mg alloy is dominant.The load vs.deflection of Charpy specimens were measured for modelling,and the effect of loading rate and temperature on load of Charpy specimens is very small because part of the specimen is in compression.The equivalent strain to fracture of the cylindrical round notched tension specimen decreases with increasing stress triaxiality;though for the flat-grooved plane strain specimen,the equivalent fracture strain remains constant over the range of stress triaxiality investigated.Because the two different specimen geometries give rise to different Lode angle values,the test results show that the Lode angle parameter is an important parameter for deformation and fracture of Mg alloys.Finite element simulations of loading of the cylindrical notched-tension and Charpy specimens were carried out using a Lode-angle dependent von Mises model,and were found to provide a reasonable description of the load-displacement curves measured in the tests.For the flat-grooved plane strain specimens,the computations under-predicted the force-displacement response measured.
