Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.TNd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy.In the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener...Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.TNd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy.In the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener,having base centered orthorhombic structure with its lattice constants of a-（β″）=0.64 nm,b-（β″）=2.22 nm, and c-（β″）=0.52 nm was identified.In the case of Mg-Nd-Zr alloy aged at 250℃,the presence ofβ″andβ′phases was identified.The crystal structure ofβ″phase was found to be DO-（19） and its orientation relationships with Mg matrix were [0001]-（β″）//[0001]-（Mg） and [01（？）0]-（β″）//[01（？）0]-（Mg）.Theβ′phase had face centered cubic structure and its orientation relationships with Mg matrix were [011]-（β′）//[0001]-（Mg） and [（？）1（？）]β′//[（？）110]）-（Mg）. The Mg-2.TNd-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.展开更多
Transmission electron microscopy was used to investigate the effect of isothermal holding temperature and time on the nano Ti-precipitates.A holding temperature was varied systematically from 400℃ to 1200℃.The isoth...Transmission electron microscopy was used to investigate the effect of isothermal holding temperature and time on the nano Ti-precipitates.A holding temperature was varied systematically from 400℃ to 1200℃.The isothermal holding was continued for 30s,300s and 900s,respectively.Nano carbides of (Ti,Nb)C were precipitated significantly at 900℃.The size of carbides was approximately 10nm at 30s holding and increased to 20～30nm at 900s holding.Isothermal holding at 1000℃ showed the increased amount of carbides larger than 100nm.At 800℃,nano (Ti,Nb)C was not observed at 30s and it was examined at 300s.The size of nano (Ti,Nb)C was smaller than that of 900℃.As the isothermal temperature decreased to 700 ℃,the nano (Ti,Nb)C was only seen at 900s holding and the size of carbides was smaller than 10nm.Nano (Ti,Nb)C was disappeared at isothermal holding below 600℃.The kinetics of nano (Ti,Nb)C precipitation were studied as a function of isothermal holding temperature and time,respectively,using the precipitate growth equations.展开更多
Dual-Phase (DP) steels are made of ductile ferrite phase and hard martensite phase.Although it became crucial in progress of automotive industry to save fuel consumption and reduce total weight of vehicles,we need mor...Dual-Phase (DP) steels are made of ductile ferrite phase and hard martensite phase.Although it became crucial in progress of automotive industry to save fuel consumption and reduce total weight of vehicles,we need more accurate estimation of distribution to mechanical properties in total amounts of specimen.DP steels have considerable difference of mechanical levels in each phase including ferrite and martensite.That is why this study focuses on deconvolution of experimental tensile curve into ferrite and martensite using EBSD for calculation of phase volume fractions and Swift equation.Nanoindentation for certain parameter of each phase was conducted to produce the deconvolution curves.展开更多
文摘Aging behavior of Mg-3.6Y-0.5Zr and Mg-2.TNd-0.5Zr alloys was investigated by microhardness measurement and transmission electron microscopy.In the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener,having base centered orthorhombic structure with its lattice constants of a-（β″）=0.64 nm,b-（β″）=2.22 nm, and c-（β″）=0.52 nm was identified.In the case of Mg-Nd-Zr alloy aged at 250℃,the presence ofβ″andβ′phases was identified.The crystal structure ofβ″phase was found to be DO-（19） and its orientation relationships with Mg matrix were [0001]-（β″）//[0001]-（Mg） and [01（？）0]-（β″）//[01（？）0]-（Mg）.Theβ′phase had face centered cubic structure and its orientation relationships with Mg matrix were [011]-（β′）//[0001]-（Mg） and [（？）1（？）]β′//[（？）110]）-（Mg）. The Mg-2.TNd-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.
文摘Transmission electron microscopy was used to investigate the effect of isothermal holding temperature and time on the nano Ti-precipitates.A holding temperature was varied systematically from 400℃ to 1200℃.The isothermal holding was continued for 30s,300s and 900s,respectively.Nano carbides of (Ti,Nb)C were precipitated significantly at 900℃.The size of carbides was approximately 10nm at 30s holding and increased to 20～30nm at 900s holding.Isothermal holding at 1000℃ showed the increased amount of carbides larger than 100nm.At 800℃,nano (Ti,Nb)C was not observed at 30s and it was examined at 300s.The size of nano (Ti,Nb)C was smaller than that of 900℃.As the isothermal temperature decreased to 700 ℃,the nano (Ti,Nb)C was only seen at 900s holding and the size of carbides was smaller than 10nm.Nano (Ti,Nb)C was disappeared at isothermal holding below 600℃.The kinetics of nano (Ti,Nb)C precipitation were studied as a function of isothermal holding temperature and time,respectively,using the precipitate growth equations.
文摘Dual-Phase (DP) steels are made of ductile ferrite phase and hard martensite phase.Although it became crucial in progress of automotive industry to save fuel consumption and reduce total weight of vehicles,we need more accurate estimation of distribution to mechanical properties in total amounts of specimen.DP steels have considerable difference of mechanical levels in each phase including ferrite and martensite.That is why this study focuses on deconvolution of experimental tensile curve into ferrite and martensite using EBSD for calculation of phase volume fractions and Swift equation.Nanoindentation for certain parameter of each phase was conducted to produce the deconvolution curves.
