The mechanism of substructure formation and grain growth 316L stainless steel by selective laser melting

Abstract

This paper aims to investigate the unique substructure and grain growth of 316L stainless steel processed by selective laser melting (SLM) and clarify the mechanism. Results showed that the grain orientation on the x-z plane parallel to the build direction was the same type as the y-z plane, which all grow along the heat flow direction to form elongated columnar grains passing through the multi-layer fusion line. The epitaxial growth direction of grains changed abruptly with the vary of temperature gradient direction. Moreover, to expound the substructure formation based on solidification theory, a finite element model was established to obtain the distribution map of cooling rate G × R and solidified morphology G/R.

Twinning behavior in deformation of SLM 316L stainless steel

“…It is also found under high magnification SEM image that grains could grow along the building direction across the molten pool boundary, and cellular and columnar substructures were distributed inside the microstructure. TEM image shows that these substructure boundaries contain high-density dislocations, constituting a dislocation network with similar morphology to conventional dislocation walls, as shown in figure 2(e), consistent with previous studies [20,21]. TEM-EDS analysis of the cell structure in figure 2(f) confirms the segregation of Cr, Mo and Ni at cell walls.…”

Influence of energy density on the microstructure and property regulation of additive manufactured pure nickel

“…Due to the absence of nucleation barriers, the direction of grain epitaxial growth is determined by the thermal gradient and growth rate during solidification. 44,45 As shown in Figure 10(e) and (f), no distinct fusion lines are observed in the IPF maps, which indicates that the continuously grown grains and the matrix grains have the same crystal structure and orientation. Therefore, the grains can grow epitaxially at the metal solid/liquid interface.…”

Inclusions and Segregations in the Selective Laser-Melted Alloys: A Review

“…Some researchers have shown the segregation of elements in the cell walls of subgrains of metals. Figure 11 displays the line scan outcomes of the cell structure using Auger electron spectrometer (AES), indicating that Mo, Cr, and Ni elements segregate in the cell wall [84]. In other study, the intensity of the Mo Lα peak increased by more than 50%, Some researchers have shown the segregation of elements in the cell walls of subgrains of metals.…”