Jaskari Matias, Ghosh Sumit, Miettunen Ilkka, Karjalainen Pentti, Järvenpää Antti
Kerttu Saalasti Institute, University of Oulu, Pajatie 5, 85500 Nivala, Finland.
Materials and Mechanical Engineering, Centre of Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu, Finland.
Materials (Basel). 2021 Oct 4;14(19):5809. doi: 10.3390/ma14195809.
Additive manufacturing (AM) is an emerging fabrication technology that offers unprecedented potential for manufacturing end-to-end complex shape customized products. However, building products with high performance by AM presents a technological challenge. Inadequate processing parameters, fabrication environment or changes in powder properties may lead to high defect density in the part and poor mechanical properties. Microstructure, defect structure, and mechanical properties of AISI 316L stainless steel pieces, additively manufactured by the laser powder bed fusion method using three different volume energy densities (VEDs), were investigated and compared with those of a commercial wrought AISI 316L sheet. Scanning and transmission electron microscopies were employed for characterization of grain and defect structures, and mechanical properties were determined by tensile testing. It was found that the number of defects such as pores and lack of fusion in AM specimens did not affect the strength, but they impaired the post-uniform elongation, more significantly when processed with the low VED. Twinning was found to be an active deformation mechanism in the medium and high VED specimens and in the commercially wrought material in the later stage of straining, but it was suppressed in the low VED specimens presumably because the presence of large voids limited the strain attained in the matrix.
增材制造（AM）是一种新兴的制造技术，为制造端到端复杂形状的定制产品提供了前所未有的潜力。然而，通过增材制造制造高性能产品面临着技术挑战。加工参数不当、制造环境或粉末性能变化可能导致零件中的缺陷密度高且机械性能差。研究了采用三种不同体积能量密度（VED）通过激光粉末床熔融法增材制造的AISI 316L不锈钢零件的微观结构、缺陷结构和机械性能，并与商用变形AISI 316L板材进行了比较。采用扫描电子显微镜和透射电子显微镜对晶粒和缺陷结构进行表征，并通过拉伸试验测定机械性能。研究发现，增材制造试样中的气孔和未熔合等缺陷数量不影响强度，但会损害均匀伸长率，在低体积能量密度加工时影响更显著。孪晶被发现是中高体积能量密度试样以及商用变形材料在拉伸后期的一种活跃变形机制，但在低体积能量密度试样中受到抑制，可能是因为大量孔洞的存在限制了基体中达到的应变。
