造孔剂法制备孔隙率可控的多孔镍钛合金

用常规粉末冶金烧结法结合造孔剂技术制备了多孔镍钛形状记忆合金.研究结果表明,孔隙特征主要取决于所用造孔剂的尺寸和形貌,而孔隙率可以通过加入造孔剂的含量来调控;所制备合金的主要成分是B2相和B19'相的NiTi,在经高温固溶处理后仍有极少量的Ti2Ni,Ni3Ti和Ni4Ti3等杂质相存在,而且合金杂质相的含量随造孔剂加入量的增加而相应提高.对合金的相变热分析表明,在从高温降至低温过程中多孔镍钛发生特殊的三阶段相变,这主要是由合金成分和相组成在晶界的不均匀造成的.最后,研究表明相变对多孔镍钛合金的阻尼性能(内耗)有独特的影响,而孔隙率对阻尼的影响则不明显.

Porous Titanium-nickel Alloys with Adjustable Porosity Fabricated Using Pore-forming Agent and Conventional Sintering

Porous nickel-titanium shape memory alloys (NiTi SMAs) with adjustable porosity were fabricated successfully by adding pore-forming agent ammonium bicarbonate and conventional sintering. It was found that the pore characteristics depended mainly on the shape and size of ammonium bicarbonate particles used, and the porosity of the alloys could.be tailored by controlling the amount of ammonium bicarbonate added. The porous NiTi SMAs fabricated mainly consisted of B2 and B19' NiTi phases, while less Ti2Ni, Ni3Ti and Ni4Ti3 phases were found even after a high temperature solution treatment. It was also found that the impurity phases increased in the porous alloys due to the addition of the pore-forming agent. In addition, a special 3-stage phase transformation took place in the porous NiTi SMAs, which was attributed to the inhomogeneity of compositions and phase constituents at grain boundaries. Moreover, phase transformation shows obvious influences on the damping behavior of the fabricated porous NiTi SMAs, while the influence from porosity was not obvious.