Non-equilibrium microstructure, crystallographic texture and morphological texture synergistically result in unusual mechanical properties of 3D printed 316L stainless steel
Non-equilibrium microstructure, crystallographic texture and morphological texture synergistically result in unusual mechanical properties of 3D printed 316L stainless steel
复制标题
DOI：
10.1016/j.addma.2019.04.016
复制
发表时间：
2019-08-01
影响因子：
11
通讯作者：
Suwas, Satyam
中科院分区：
文献类型：
--
作者：
Bahl, Sumit;Mishra, Sumeet;Suwas, Satyam
介绍了316L不锈钢在选择性激光熔化（SLM）过程中织构和显微组织的演变机制及其对力学响应的综合影响。具有纤维结构的长柱状晶粒< 110 >||构建方向（BD）在SLM印刷材料中演变。纤维质地是更强的水平建设相比，垂直建设。双向扫描策略的使用迫使晶粒在单个印刷层内存在的熔池上外延生长。< 110> ||BD织构的演化是由于[100]沿着最大热梯度的外延和生长之间保持平衡的结果。高位错密度和不受晶粒尺寸影响的超细胞状组织赋予了316L高强度。较低的平均施密德因子和较小的有效晶粒尺寸在水平构建的优点的晶体学和形态学的纹理，分别给予较高的屈服强度比垂直构建。与垂直构造相比，水平构造在变形的早期阶段表现出更高的应变硬化速率，这是由于更高的晶体学织构依赖的孪晶。然而，较高的位错湮灭率导致水平构建的应变硬化率持续下降。相比之下，在垂直构建中保持稳定的应变硬化速率，这导致比水平构建更高的延展性。总之，本文阐述的非平衡微观结构和织构（晶体学和形态学）在调节机械性能方面的作用可用于设计316 L不锈钢的增材制造结构部件。
Mechanisms underlying the evolution of texture and microstructure during selective laser melting (SLM) and their combined effects on the mechanical response of 316L stainless steel are presented. Long columnar grains with a fiber texture < 110 > || build direction (BD) evolved in the SLM printed material. Fiber texture was stronger in the horizontal build compared to the vertical build. Use of bidirectional scanning strategy enforced epitaxial growth of grains across melt pools present within a single printed layer. < 110> || BD texture evolved as a consequence of maintaining the balance between epitaxy and growth of [100] along maximum thermal gradient. High dislocation density and not grain size effect of the ultra-fine cellular structure, imparted high strength to 316L. Lower average Schmid factor and smaller effective grain size in the horizontal build by virtues of crystallographic and morphological textures, respectively, imparted higher yield strength than the vertical build. The horizontal build demonstrated higher strain hardening rate in the early stages of deformation compared to the vertical build due to higher crystallographic texture dependent twinning. However, the higher rate of dislocation annihilation led to a continuous decline in the strain hardening rate of the horizontal build. In contrast, a stable strain hardening rate was maintained in the vertical build, which led to higher ductility than the horizontal build. In summary, the roles of non-equilibrium microstructure and texture (crystallographic and morphological) in regulating mechanical properties elucidated here, can be utilized in designing additively manufactured structural components of 316L stainless steel.