Effect of Post-Processing Heat Treatment Temperature on Microstructural Evolution and Mechanical Properties of the Ti-6Al-2Sn-4Zr-2Mo Alloy Fabricated by Laser Powder Bed Fusion

TL;DR

This study examines how heat treatment after 3D printing affects the strength and structure of a titanium alloy, finding that higher heat treatment temperatures improve flexibility while maintaining high strength.

Contribution

The novel contribution is demonstrating that post-processing heat treatment can optimize mechanical properties of Ti-6242 alloy produced via laser powder bed fusion.

Findings

Heat treatment increases tensile elongation while gradually decreasing yield and ultimate tensile strength.

Microstructural changes like α′ martensite decomposition and coarsening correlate with mechanical property evolution.

The lowest yield strength after treatment remains comparable to conventionally processed Ti-6242 alloys.

Abstract

In this study, the influence of post-processing heat treatment on microstructure and mechanical properties of Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) alloy fabricated by laser powder bed fusion (L-PBF) was investigated. The mechanical properties of the as-built and heat-treated samples with various temperatures (600–850 °C) were evaluated using a tensile test at room temperature. After heat treatments, both yield strength (YS) and ultimate tensile strength (UTS) gradually decreased, while the tensile elongation tended to increase as the heat treatment temperature increased. These variations were closely related to the microstructural evolution caused by heat treatment. Specifically, the decomposition of α′ martensite into the α + β lamellar structure and subsequent coarsening were promoted with increasing temperature, leading to stress relief and improved dislocation storage capability, which resulted in the variation in mechanical properties. Notably, although the mechanical strength was reduced after heat treatment with increasing temperatures, the lowest yield strength and ultimate tensile strength were measured as 1086.4 ± 16.5 and 1135.0 ± 15.0 MPa, respectively, which are comparable to or higher than those of conventionally processed Ti-6242. As a result, the post-processing heat treatment could be an effective approach to achieve desirable performance for targeted applications.

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