打印参数对电子束增材制造Ti-Ni合金性能的影响

Influence of Manufacturing Parameters on the Properties of Electron Beam Melted Ti-Ni Alloy

利用SEM、XRD、DSC、TEM和等轴压缩等实验手段,研究和分析了打印参数焦距补偿(FO)和速度函数(SF)对电子束增材制造(EBM)制备的Ti-Ni合金显微组织、相组成、相变行为以及压缩性能的影响。结果表明:EBM打印参数FO和SF在一定范围内调节时均可制备出相对密度较高(97%以上)的Ti-Ni合金样品。由于EBM电子束的功率大,在预合金粉末快速受热熔化过程中,Ni元素的挥发效应大于富Ti相Ti2Ni析出效应对相变温度的影响,使得制备Ti-Ni块体的相变温度大于相应的预合金粉末,而打印参数FO和SF对制备样品的相变温度、相组成以及显微硬度的影响较小。EBM制备过程中在样品内部引入不同种类的缺陷类型,使得TiNi合金样品在相对密度接近的情况下压缩性能表现出极大的差异,其中贯穿型裂纹缺陷对压缩性能的影响最大,使Ti-Ni合金的强度和塑性大幅度降低。

Electron beam melting(EBM)is one of the additive manufacturing technologies which can be used to fabricate the complex structure and shape samples.Until now,there are few literatures published about the properties of Ti-Ni samples produced by EBM.In this work,the influence of two important manufacturing parameters of focus offset(FO)and speed function(SF)on the density,phase content and transformation behavior,microstructure and mechanical properties was investigated for the equiatomic Ti-Ni shape memory alloy fabricated by EBM used DSC,XRD,SEM,TEM and electronic universal testing machine.The results showed that all the Ti-Ni samples had a high relative density beyond than 97%for fabricated by different combinations of FO and SF in the selected range.The corresponding phase transformation temperatures for all the Ti-Ni samples fabricated by EBM were higher than the prealloyed Ti-Ni powder,due to the effect of evaporation of Ni element higher than that of the formation of Nirich Ti2Ni phase during the quickly melting and solidification process.On the other hand,the EBM manufacturing parameters of FO and SF had limited influence on the phase contents,phase transformation temperatures and Vickers hardness.Due to the feature of the EBM fabricating method,the different types of defects would be introduced in the Ti-Ni solid samples.Though all the samples had similar high relative density,the performance of the compression behavior were shown great difference,and the crack defect had the larger effect than the gas and lack-of fusion porosities on the compression fracture stress and strain.