Effect of Process and Post-Process Conditions on the Mechanical Properties of an A357 Alloy Produced via Laser Powder Bed Fusion

Alberta Aversa,Paolo Fino,Sara Biamino,Massimo Lorusso,Matteo Pavese,Francesco Trevisan,Flaviana Calignano,Diego Manfredi,Mariangela Lombardi,Elisa Ambrosio

doi:10.3390/met7020068

Abstract

A357 samples were realized by laser powder bed fusion (LPBF) on building platforms heated up to different temperatures. The effect of the preheating temperature and of the post processing heat treatment on the microstructure and the mechanical properties of the samples was studied. It was demonstrated that building platform heating can act as an in situ ageing heat treatment following the fast cooling that arises during laser scanning. A 17% higher ultimate tensile strength was achieved by the selection of the optimum building platform temperature. Moreover, the possibility to further increase the mechanical properties by means of a direct ageing heat treatment was investigated.

Highlights

Additive manufacturing (AM) is defined by the ISO/ASTM 52900:2015 standard as the “process of joining materials to make parts from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing and formative manufacturing methodologies”
The laser powder bed fusion (LPBF) process belongs to this class and uses a laser as its energy source
The FESEM micrographs of the samples’ cross-sections, illustrated in Figure 2, reveal that in all cases, an extremely fine microstructure, constituted by α-Al cells surrounded by the eutectic, is formed as a consequence of the rapid solidification

Summary

Introduction

Additive manufacturing (AM) is defined by the ISO/ASTM 52900:2015 standard as the “process of joining materials to make parts from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing and formative manufacturing methodologies”. AM technologies are increasingly employed in the aerospace, automotive and medical fields thanks to the high level of design freedom and the interesting microstructures which can be obtained [1,2]. These processes allow the production of complex parts which would be difficult or impossible to produce with conventional processes and that would require several manufacturing steps and high material and energy consumption. The ISO/ASTM 52900:2015 standard refers to powder bed fusion (PBF) as the “additive manufacturing process in which thermal energy selectively fuses regions of a powder bed”. LPBF is very attractive thanks to its extremely high cooling rates that can reach 106 Ks− 1 [4], that make it possible, as recently reported in some studies, to obtain metastable structures and supersaturated solid solutions [5,6,7]

Methods

Results

Conclusion