Fe含量对等原子比NiTi形状记忆合金微观组织、相变行为和显微硬度的影响

Effect of Fe content on microstructure,phase transformation behavior and microhardness of the equiatomic NiTi shape memory alloy

采用光学显微镜、扫描电子显微镜、X射线衍射仪、差示扫描量热仪和显微硬度计等测试手段,研究了Fe含量对Ni 50-x/2 Ti 50_(x/2) Fe_(x)(x=0.5%~3.5%)形状记忆合金微观组织、相变行为和显微硬度的影响规律.结果表明:NiTiFe三元形状记忆合金组织主要由Ni 4.8 Ti 5Fe 0.2相、Ni 3Ti相和基体组成,随着Fe含量的增加,合金组织中等轴晶粒尺寸逐渐增大;合金的相变温度,随Fe含量的增加迅速下降;合金的显微硬度随Fe含量的增加而急剧增加,与Fe含量呈正相关关系,当x=3.5%时达到最大值469.91 HV.

The effect of Fe content on the microstructure,phase transformation behavior and microhardness of Ni 50-x/2 Ti 50-_(x/2) Fe_(x)(x=0.5-3.5 at.%)alloys was investigated by an optical microscope(OM),scanning electronic microscope(SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC)and microhardness tester.The results show that the grain size of the alloy with the equiaxed structure increases with increasing Fe content,and the microstructure of NiTiFe ternary shape memory alloy consists of Ni 4.8 Ti 5Fe 0.2 phase,Ni 3Ti phase and the matrix.Furthermore,it is observed that the phase transformation temperatures of the alloys decline rapidly with the increase of Fe content.In the meantime,the microhardness of the alloys increased evidently with the increase of Fe fraction.It is also found that there is a positive correlation between Fe content and the microhardness of NiTiFe ternary shape memory alloy,reaching a maximum value of HV 469.91 at x=3.5 at.%.