Experimental Study Of The Behavior Of Defects And D Electrons In NiTi Shape Memory Alloy At Low Temperature

Near-equiatomic binary NiTi alloys have been widely applied in many fields of aviation and biomedicine and have become the most successful of the shape memory alloys as a result of their combination of good shape memory effect, superelasticity, anticorrosion and biocompatibility. When the temperature decreases or the stress induces, the martensitic transformation will happen in NiTi alloys with the crystal structure changing from CsCl(B2) to monoclinic B19'.When being heated, the parent phase will be restored, showing shape memory effect consequently. A variety of methods have been used in the studies of NiTi alloys. It has been shown that the microdefect and electronic structure in NiTi alloys play an important role on shape memory effect and martensitic transformation. More experimental evidences are needed to understand the micromechanism on the variation of microdefects and electron densities with the temperature in NiTi alloys.In present work, the coincidence Doppler broadening spectra of positron annihilation radiation of NiTi, NiAl alloys, single crystal of Si, and pure metals, such as Fe, Co, Al, Nb, Cu, Ni, Ti have been measured. The signal of 3d-shell...