Study on preparation and anodic oxidation of gradient porous NiTi alloy

摘要

Gradient porous NiTi alloys were prepared by powder metallurgy method using NH_4HCO_3 as space-holder and modified by direct current-pulse anodic oxidation technology in low temperature. Pore characteristic and phase composition of gradient porous NiTi alloys were studied. Microstructure, composition, anti-corrosion and Ni ion release behavior of surface film were observed. The results show the porosity of porous NiTi alloys decreases from 53.2% to 42.8%, when the content of NH_4HCO_3 varying from uniformity to gradient distribution. The sintered gradient porous NiTi alloys composes with TiNi, T12M and T1N13 phases. After anodic oxidation, Ti oxidation film with the thick of 240nm was formed on the gradient porous NiTi alloy. The corrosion resistance of gradient porous NiTi alloy was obviously improved and the rate of Ni release was significantly reduced.