扫描间距对激光选区熔化NiTi形状记忆合金相变行为及力学性能的影响

Effect of Hatch Spacing on Phase-Transformation Behavior and Mechanical Properties of NiTi Shape Memory Alloy Fabricated Using Selective Laser Melting

激光选区熔化(SLM)增材制造技术为NiTi形状记忆合金复杂结构件的制造开辟了新途径,已成为智能材料领域的研究热点之一。本课题组采用光学显微镜、电子显微镜、X射线衍射仪、差式扫描量热仪、万能材料试验机等,重点研究了扫描间距h对SLM成形NiTi合金相对密度、组织结构、相变行为及力学性能的影响。结果表明:线能量密度在100~250 J/m范围内时,可以获得连续且稳定的单熔道试样;随着扫描间距h从115μm减小到64μm,SLM成形的NiTi合金块体中的NiTi(B2)相含量有所减少,相对密度增大,表面粗糙度减小,相变温度M_(s)呈逐渐升高的趋势。扫描间距h=77μm时成形的NiTi块体试样的综合性能最佳:相对密度为98.5%,抗压强度和抗拉强度分别为3351 MPa和839 MPa,第1次压缩循环后的可回复应变为5.99%,应变回复率高达97%,第10、第20次压缩循环后的可回复应变分别为5.77%和5.75%。

Selective laser melting(SLM)is a new way to manufacture complex NiTi shape memory alloy parts and has become one of the research hotspots in the field of smart materials.In this paper,an optical microscope,a scanning electron microscope,an X-ray diffractometer,a differential scanning calorimeter,and a universal material testing machine were used to investigate the effect of hatch spacing(h)on the relative density,microstructure,phasetransformation behavior,and mechanical properties of a NiTi alloy fabricated using the SLM process.The results demonstrate that when the line energy density was within the range of 100-250 J/m,a continuous and stable single track could be obtained.As the hatch spacing decreased from 115 to 64μm,the content of NiTi(B2)phase and the surface roughness decreased while the relative density and the transformation temperature gradually increased.The NiTi sample fabricated with h=77μm exhibited the best overall performance.The relative density,compressive strength,and tensile strength were 98.5%,3351 MPa,and 839 MPa,respectively.After the first compression cycle,the recoverable strain was 5.99%and the strain recovery rate was 97%.After the 10 th and 20 th compression cycles,the recoverable strain remained 5.77%and 5.75%,respectively.