Effect of Hot Isostatic Pressing and Powder Feedstock on Porosity, Microstructure, and Mechanical Properties of Selective Laser Melted AlSi10Mg

Abstract

AlSi10Mg tensile bars were additively manufactured using the powder-bed selective laser melting process. Samples were subjected to stress relief annealing and hot isostatic pressing. Tensile samples built using fresh, stored, and reused powder feedstock were characterized for microstructure, porosity, and mechanical properties. Fresh powder exhibited the best mechanical properties and lowest porosity while stored and reused powder exhibited inferior mechanical properties and higher porosity. The microstructure of stress relieved samples was fine and exhibited (001) texture in the z-build direction. Microstructure for hot isostatic pressed samples was coarsened with fainter (001) texture. To investigate surface and interior defects, scanning electron microscopy, optical fractography, and laser scanning microscopy techniques were employed. Hot isostatic pressing eliminated internal pores and reduced the size of surface porosity associated with the selective laser melting process. Hot isostatic pressing tended to increase ductility at the expense of decreasing strength. However, scatter in ductility of hot isostatic pressed parts suggests that the presence of unclosed surface porosity facilitated fracture with crack propagation inward from the surface of the part.

Effect of HIP process and subsequent heat treatment on microstructure and mechanical properties of direct metal laser sintered AlSi10Mg alloy

“…As stress-relieved and rough surface finishes (Finfrock et al, 2018). Gas porosities can be due to entrapped gases (such as hydrogen) in the powder particles or due to the surface oxides in the particle surfaces (humidity), and seen mostly in spherical shape.…”

Deep learning prediction of stress fields in additively manufactured metals with intricate defect networks

“…The ubiquitous presence of porosity defects in additively manufactured metals is known to limit the mechanical properties compared to fully-dense materials during quasistatic and dynamic monotonic mechanical loading [1,2], as well as cyclic fatigue loading [3][4][5]. During laser powder bed fusion (L-PBF) processing, elaborate networks of voids can form by several mechanisms such as melt pool instabilities, incomplete melting of powder, and entrapped gas porosity [6,7].…”

High-Throughput Statistical Interrogation of Mechanical Properties with Build Plate Location and Powder Reuse in AlSi10Mg

“…Powder was kept in an argon atmosphere throughout the process. Finfrock et al 36 compared properties of specimens printed with the fresh and stored powder as well as hot isostatically pressed specimens.…”

“…Si content and grain structure were also shown not to change significantly between builds. 36 Moisture in powder can cause porosity in AlSi10Mg associated with elevated levels of hydrogen and oxygen content. 23,35,48 The oxygen and hydrogen content of four build plates, obtained from LECOÒ analysis, 49 is presented in Fig.…”