2025 Volume 72 Issue 10 Pages 201-209
An α+β titanium alloy, Ti-6Al-4V (Ti-Al-V), is widely used in laser powder bed fusion. However, in this process, Ti-Al-V often suffers from limited ductility due to the formation of unintended martensitic microstructures. To address this issue from the alloy design perspective, the present study explores various β phase stabilizing elements which can facilitate in-situ decomposition of martensite into desirable α+β microstructures. Based on high diffusivity and sluggish eutectoid reactions, Cr, Mn, and Fe were selected as elements of interest to compare with V in Ti-Al-V. Using the CALPHAD approach, alloy compositions of Ti-Al-V, Ti-Al-Cr, Ti-Al-Mn, and Ti-Al-Fe were designed to exhibit identical β transus temperatures, and the corresponding alloys were then fabricated by powder metallurgy. Following supertransus heat treatment and subsequent water quenching, Ti-Al-V and Ti-Al-Cr formed a single α’ martensitic phase, while Ti-Al-Mn and Ti-Al-Fe exhibited α’+β phases. A subsequent heat treatment at 600°C led to the β phase formation in all alloys. However, this isothermal treatment also caused the formation of intermetallic compounds in Ti-Al-Fe and Ti-Al-Cr. Consequently, Mn was found to be the most effective and reliable β stabilizer for in-situ α+β formation based on the facilitative formation of β phase, and suppression of detrimental intermetallic compounds.
