Microstructure and superelasticity of porous NiTi alloy
Science in China Series E: Technological Sciences
The microstructure, porosity, phase composition and superelasticity (SE) in porous NiTi alloys produced by elemental powder sintering are examined by SEM, Image Analysis and XRD. It is found that it is feasible to produce porous NiTi alloy by elemental powder sintering, and the porosity of sintered porous NiTi alloy is in the range of 36.0%41.5%. The pores are interconnected and the microstructure is sponge-like. Meanwhile, porous NiTi alloy has good SE. XRD patterns show that there is no pure
... Ni in alloy sintered at 1223 K-9 h. Compared with the biomedical criteria for choice of implanting materials, porous NiTi alloy is satisfying to a great degree. The mechanical deformation behavior of biological materials, which each has a high recoverable strain (more than 2%), is very different from that of common metallic materials and only the SE of shape memory alloys is similar to it . NiTi alloy also has excellent mechanical properties, good corrosion resistance and biocompatibility. Recently, porous NiTi alloy has become a central item of concern as it possesses lots of advantages as follows. The yield stress of bulk NiTi alloy produced from conventional method is very high and difficult to adjust by subsequent heat treatment. While by obtaining various porosity and pore size through controlling sintering conditions, it is easy to adjust the yield stress of porous NiTi alloy to match that of replaced organism. Moreover, the compressibility and porous structure are beneficial for the ingrowth of bone mineralization tissue and fibrous tissue, which makes the fixation of implant much more natural and reliable. The good shape memory effect (SME) and unique volume memory effect  can simplify the implanting process of medical implant and make patients suffer less pain. Additionally, porous NiTi alloy can be used together with bulk NiTi alloy to exert complicated function. Because of these features, porous NiTi alloy shows great advantage and medical value over other medical materials in prosthesis and substitution of bone, joint, teeth and other surgery implanting materials  . It can be speculated that this biomedical materials, a product of multi-courses, has great exploitation value. -95 -"863" Committee for High Technique and Committee for Biomedical Materials. The purpose of this study is to prepare porous medical NiTi alloy and try to make it satisfy the requirement of biomedical materials, and speed the research and exploitation of porous NiTi alloy in China.