Effect of Ni4Ti3 precipitates on phase transformation behavior of NiTi superelastic shape memory alloy
The temperature-induced phase transformation and stress-induced phase transformation of coherent precipitated phase and semi-coherent precipitated phase block/pillar model were simulated by molecular dy-namics method with second nearest neighbor correction embedded atom potential.The effect of Ni4Ti3 precipitates on the phase transformation behavior of NiTi shape memory alloy was analyzed.The results show that the elastic stress field induced by the intrinsic strain of Ni4Ti3 precipitated phase has an important effect on the type,nucle-ation location and distribution of martensitic variants during the phase transformation.During the temperature-induced phase transformation,the coherent precipitated phase promotes the nucleation and growth of some mar-tensitic variants,which can significantly increase the martensitic transformation starting temperature of NiTi shape memory alloy.During the stress-induced phase transformation,the Ni4Ti3 precipitated phase makes the mar-tensite nucleate earlier than the non-precipitated phase region,resulting in a decrease in the phase transforma-tion stress,inhibiting the martensite detwinning,and reducing the hysteresis loop of the stress-strain curve.
国家科技期刊平台
NSTL
万方数据
