Relationship between mechanical property and microstructure of NiTi shape memory alloy

The relationship between mechanical property and microstructure of NiTi shape memory alloy has been studied. It was founded that with increasing prestrain the memory recovery rate decreased, but the recovery stress and the recovery strain increased first and then decreased. The recovery stress and the recovery strain reached maximum at about 11% prestrain. The TEM(Transmission Electron Microscope) results of the alloy indicated that the microstructures with different prestrain of the alloy had obvious characters. At 9% prestrain, the martensite anamorphosis of the alloy still presented self-cooperation configuration, and some martensites have become thick obviously because of tropism. When the prestrain was 11%, the martensite anamorphosis has become completely thick and tropism became consistent. As the prestrain increased to 13%, the microstructures of the alloy have become disordered, the tropism became inconsistent and the interface became blurry.