Heat-treatment effects on a bimetallic additively-manufactured structure (BAMS) of the low-carbon steel and austenitic-stainless steel

A bimetallic additively-manufactured structure (BAMS) is a type of functionally-graded multi-material structure used for achieving different complementary material properties within the same structure as well as cost optimization. Wire + arc additive manufacturing (WAAM) offers the capability to fabricate the BAMS in a simultaneous or sequential way. To fully utilize the benefits of the BAMS, the interfacial joint should be strong, and each of the constituents should have reasonable mechanical integrity. For this, a BAMS of low-carbon steel and austenitic-stainless steel was fabricated using a gas-metal-arc-welding (GMAW)-based WAAM process. Then, the BAMS was heat-treated at a range of 800 degrees C to 1100 degrees C and 30 min to 2 h. This resulted in 35% and 250% increases in the ultimate tensile strength and elongation, compared to the as-deposited BAMS. After the heat-treatment, the failure location moved from the low-carbon-steel to the stainless-steel side. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAx), and the Vickers hardness test were used to characterize the BAMS. In this paper, it is experimentally validated that heat-treatment at 950 degrees C-1 h is the near-optimal condition for the BAMS.