SPS制备NiTi表面多孔梯度合金的组织演变与力学性能研究

Microstructure Evolution and Mechanical Properties of Porous Surface NiTi Gradient Alloy Prepared by Spark Plasma Sintering

利用放电等离子烧结技术制备了基体为NiTi、表面为多孔NiTi的生物医用梯度合金,研究了烧结温度对梯度合金的微观结构、显微组织演变、表面孔隙特征及力学性能的影响。结果表明:随着烧结温度升高,合金由Ti、Ni、Ti_2Ni、Ni_3Ti混合相逐渐演变为以NiTi相为主及少量残留Ti_2Ni、Ni_3Ti相组成的组织,基体与多孔层界面处裂纹及缺陷逐渐减少并形成稳定的冶金结合,内外层晶粒不断细化,但过高的烧结温度会导致多孔层孔隙融合连通,使得梯度结构遭到破坏,同时表面多孔层孔隙率与平均孔径呈缓慢减小趋势;合金压缩弹性模量随烧结温度升高变化不明显,而抗压强度呈显著增大趋势。与块体NiTi合金及多孔NiTi合金相比,所制备梯度合金不仅具有良好的界面结合和表层孔隙特征、较高的抗压强度及较低的弹性模量,还具有优异的超弹性性能。

The effects of different sintering temperature on the microstructure, microstructural evolution, surface porosity and mechanical properties of porous surface NiTi biomedical gradient alloy were investigated. The results show that the gradient alloy originally consists of complex Ti, Ni, TiENi, Ni3Ti mixed phase; then it gradually transforms into NiTi phase with a little TiENi, Ni3Ti phase with increasing of the sintering temperatures. The cracks and defects at the interface between the matrix and the porous layer are gradually reduced and a stable metallurgical bonding is formed. The inner and outer grains are refined continuously, but the higher sintering temperature leads to the porosity fusion of the porous layer, resulting in the damage of the gradient structure. The porosity and the average pore size of surface layer decreases slowly. The compressive elastic modulus of the alloy changes with the sintering temperature slightly, while the compressive strength shows a significant increase trend. Compared with bulk NiTi alloy and porous NiTi alloy, the prepared gradient alloy has good interface bonding and surface pore characteristics, high compressive strength and low elastic modulus; it also has excellent super-elastic properties