Thermo-mechanical post-treatment: A strategic approach to improve microstructure and mechanical properties of cold spray additively manufactured composites

In recent time, cold spray additive manufacturing (CSAM) has emerged as a promising solid state manufacturing technique to produce thick deposits of pure metal, alloys and composites with limited risk of oxidation, phase transformations, and residual thermal stresses. This preliminary study highlights an effective post spray thermo-mechanical treatment (TMT) that can be used to efficiently heal out splat boundaries and rejuvenate mechanical properties of the as-sprayed composites. CSAMed B4C/Al composite was subjected to a series of TMTs via heating at similar to 500 degrees C in the furnace for 2 h followed by unidirectional rolling treatments with thickness reductions of 20, 40 and 60% in 1, 2 and 3 passes, respectively. Microstructural investigations revealed that as the thickness reduction was increased from 20%, matrix grains were extensively refined due to continuous dynamic recrystallization (CDRX). Moreover, bonding between Al/Al splats and B4C/Al interfaces was remarkably improved due to enhanced inter-particle diffusion activity. Consequently, yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the as-sprayed composite were enhanced simultaneously. The TMTed sample with thickness reduction of 60% showed highest values of UTS and EL compared with the corresponding values of as-sprayed and conventionally heat treated samples. (C) 2018 Elsevier Ltd. All rights reserved.