Exploiting Electropulses to Optimize Microstructure in Ti–6Al–4V Fabricated by Selective Laser Melting

Abstract

A post-heat treatment is necessary to finely adjust the desired microstructure and mechanical properties of Ti alloys produced by additive manufacturing. This research offers a comprehensive study of how electropulsing treatment (EPT) changes the microstructure and microhardness of Ti–6Al–4V alloy fabricated by selective laser melting. It verifies the potential benefits of using EPT instead of the conventional furnace heat treatment (FHT). The microstructural evolution was interpreted based on the number and magnitude of electropulses, which were then compared with FHT samples treated at the same temperatures and durations. Notably, the harmful columnar microstructure completely disappeared though the application of multiple electropulses at a current density of 20 A mm−2. Such a result was not attained by the FHT counterpart using the same peak temperature (1319 K) and duration (23 min). Furthermore, the EPT specimen exhibited a significant β-grain refinement. The accelerated atomic diffusion flux, one of athermal effects of EPT, resulted in the fast transformation of columnar microstructure into fine and equiaxed prior-β grains. The microhardness was affected by both lath thickness and phase constituents in the as-built alloy, whereas it was only governed by the former after the post-heat treatments. Utilizing EPT as an alternative post-heat treatment can effectively alleviate the microstructural inhomogeneity of additively manufactured metals. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s) under exclusive licence to The Korean Institute of Metals and Materials.