梯度孔隙率与大孔隙尺寸 NiTi 形状记忆合金的 制备及其相变和超弹性行为

Porous NiTi shape memory alloys with gradient porosity, large pore-size and satisfactory mechanical property were fabricated by using pore-forming agent combining with hot isostatic pressing (HIP) and conventional sintering process (CS). The results showed that the porosity ratio and pore-size can be changed in the ranges of 30%-61% and 50-500 μm respectively under the reasonable addition amount of pore-forming agent (NH₄HCO₃) and sintering process. XRD and DSC proved the prepared samples exhibit multi-stage martensitic transformations, the transition temperature decreases with increasing porosity. The sample with radial gradient porosity shows good compression property and excellent linear superelasticity higher than 4%.