激光3D打印制备多孔结构不锈钢的组织及压缩性能研究

采用316L不锈钢粉末基于激光3D打印技术(Laser 3D printing,L3DP)制备多孔结构试样与致密试样,研究其微观组织结构及压缩性能。首先对两种试样进行显微组织分析及显微硬度测量;随后进行压缩试验,获得两种试样工程应力-应变曲线并比较其压缩性能;最后利用有限元数值模拟动态再现两种试样的压缩过程,分析变形过程中金属流动与宏观工程应力-应变曲线的内在联系。结果表明:L3DP成型多孔结构不锈钢部件内部组织具有典型的层带结构,主要由沿不同方向生长的柱状晶构成,晶粒尺寸由中心白亮组织向外逐层递增,各层带成分分布均匀且显微硬度在170~190 HV之间变化;L3DP成型多孔不锈钢部件的屈服强度为380 MPa,压缩弹性模量为23.0 GPa,具有良好强塑性匹配;压缩仿真试验显示多孔结构部件内部孔隙在应力作用下逐渐弯曲,最终由流动金属压合填充,由此导致整体空间体积减小,所以相同工程应力下多孔结构部件的工程应变较大。

Microstructure and Compressive Property of Porous Stainless Steel Fabricated by Laser 3D Printing

Porous sample and dense sample are fabricated by laser 3D printing (L3DP) using 316L stainless steel powder and their microstructure and compressive property are revealed. Firstly, analysis of microstructure and micro hardness are performed on both samples. Engineering stress-strain curves of both samples are obtained by the compressive test and their compression performance are compared. Finally, the dynamic compressive process of both samples is simulated by ABAQUS and the internal relations between metal flow and macro engineering stress-strain curve are analyzed. The results show that the typical band structure of microstructure exists in porous 316L stainless steel parts which fabricated by L3DP. It is mainly consisted of columnar dendrites which grew epitaxial. Grain size gradually increases outward from the white bright center. The composition of each band distributes uniform and the micro hardness changes between 170-190 HV. Porous 316L stainless steel parts fabricated by L3DP have a good matching of strength and plasticity, which yield strength is 350MPa and elasticity modulus is 23.0 GPa. Simulation compression experiment shows that pores inside porous parts gradually become bending and finally fill by flow metal, so that the overall space volume decreases and this is the reason why the engineering strain of porous parts are bigger under the same engineering stress.