中文摘要：

选区激光熔化技术在复杂零部件的制造领域显示出强大的优势,但打印件的组织与综合性能还有待于进一步优化。采用选区激光熔化技术制备了316L不锈钢的拉伸试样,分析了试样不同区域的组织特征,测试了其拉伸力学性能。结果表明,其组织形貌主要为胞状晶,但在某些“微熔池”内晶粒生长方向不相同,近乎于相互垂直,从而在同一视野中呈现出典型的细小柱状晶（亚晶）和近似六边形“胞晶”共存的组织特征。试样的抗拉强度与传统工艺相比有较大提高,但延伸率有所降低。这主要是由于选区激光熔化是快速熔化与冷却凝固的过程,其选区熔化的特征使得不同区域的激光入射角度、选区熔化扫描方式、“熔池”散热条件各不相同,导致不同区域呈现复杂的结晶过程,形成不同特征的微区组织。由于冷却速度较快,所得细小柱状晶的直径为亚微米级,致密分布,显著提高了材料的抗拉强度。但由于晶粒生长明显的方向性,使得拉伸过程中晶粒在不同方向的塑性变形不均匀,相互牵制,加之熔合线界面处不可避免的内应力,导致延伸率降低。

英文摘要：

The selective laser inching technology shows great advantages in the field of manufacturing of complex palls,but tile organization and the comprehensive performance of a printed copy remains to be further optimized. Specimens of 316L stainless steel is fahricated by selective laser melting technology,the microstructure characteristics of different regions are analyzed,the tensile mechanical properties are tested. The resuhs show that the morphology is mainly columnar crystal,but in some ＂micro pool＂ the grains growth directions are ,~ot the san]e,and almost perpendicular to each other,which shows the organizational characteristics of coexistence of typical fine columnar crystals （subg,＇ailO and hexagonal ＂cellular crystal＂ in tbe same field of vision. Comparing with the traditional technology ,the tensile strength of specimen greatly improves,but the elongation decreases. This is nminly due to the selective laser mehing process is rapid melting and solidification, the selective melting features makes the laser incident angle in different regions, selective melting scan method and ＂pool＂ cooling conditions vary.which leads to complicated cstallization process in different regions and forms micro area organizations witlh different characteristics. Because of fast cooling speed,the diameter of fine columnar crystal is submicron,and dense distribution,which significantly enhances the tensile strength of material. However,due to the obvious directionality of grain growth,the plasticity deformation of grains in different directions in the process of drawing is not uniform and restrains each other,additionally the inevitable internal stress on the interface of fusion line,resuhing in a reduee in elongation.