The characteristic sub-grain cellular structures widely observed in additively manufactured metals and alloys play an important role during plastic deformation. In the present study, the influence of cell boundaries on the mechanical response of a directed energy deposited 316 L stainless steel was investigated using site-specific micro-compression tests of single and bi-crystal micro-pillars with various cell boundary orientations relative to the compression direction. In an effort to distinguish between grain boundary and cell boundary effects, single-crystal micro-pillars were fabricated from strategically selected regions within a single grain, but with variable cell boundary orientations. Bi-crystal pillars that cross grain boundaries were also investigated. While the stress-strain curves for single-crystal micro-pillars exhibit serrations and a mild strain hardening, those for bi-crystal micro-pillars are absent of serrations and show higher strain hardening rates. Moreover, despite differences in cell boundary orientation, single-crystal micro-pillars with the same crystal orientation (i.e., from the same grain) show similar yield strengths and strain hardening behavior, indicating a limited effect of cellular structure on plastic anisotropy. The results further demonstrate that although cell boundaries can temporarily impede the motion of dislocations, corresponding to a strengthening effect, they ultimately allow dislocation transmission when the applied stress is sufficiently high. While our results suggest that cell boundaries and grain boundaries have distinct interaction mechanisms with dislocations, they also indicate that manipulation of the cellular texture may provide a pathway to engineer the properties of additively manufactured metals and alloys.

在增材制造的金属和合金中广泛观察到的特征亚晶粒细胞结构在塑性变形过程中起着重要作用。在本研究中，细胞边界对定向能量沉积的 316 L 不锈钢的机械响应的影响使用特定位置的微压缩测试研究了单晶和双晶微柱的不同细胞边界取向相对于压缩方向。为了区分晶界和晶胞边界效应，单晶微柱是从单个晶粒内战略性选择的区域制造的，但具有可变的晶胞边界取向。还研究了跨越晶界的双晶柱。虽然单晶微柱的应力-应变曲线表现出锯齿和温和的应变硬化，但双晶微柱的应力-应变曲线没有锯齿并显示出更高的应变硬化率。此外，尽管晶胞边界取向不同，但具有相同晶体取向的单晶微柱（即，来自同一晶粒）显示出相似的屈服强度和应变硬化行为，表明细胞结构对塑性各向异性的影响有限。结果进一步表明，尽管单元边界可以暂时阻止位错运动，对应于强化效应，但当施加的应力足够高时，它们最终允许位错传输。虽然我们的结果表明细胞边界和晶界与位错具有不同的相互作用机制，但它们也表明细胞纹理的操纵可能为设计增材制造的金属和合金的性能提供了途径。