Effect of Heat Treatment on Microstructure and Properties of Laser Powder Bed Fusion–Fabricated High‐strength and High‐toughness Alloy

To address low material utilization, high costs, and lengthy production cycles associated with traditional processing of high‐strength titanium alloys, this study investigates the effects of postheat treatment on the microstructure and properties of Ti‐3Al‐8V‐6Cr‐4Mo‐4Zr (Ti‐38644) titanium alloy fabricated by laser powder bed fusion (PBF‐LB). Ti‐38644 powder is used to prepare specimens via PBF‐LB. Various solution and aging treatments are applied, and the resulting changes are analyzed using optical microscopy, scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and room‐temperature tensile testing. Solution treatment eliminates molten pool boundaries and substructures in the PBF‐LB‐formed Ti‐38644, increases XRD peak intensity, reduces dislocation density, and enhanced plasticity—elongation increased from 11.9% to 15.5%. Aging induced precipitation of the secondary α phase, increasing strength to 1510 ± 2 MPa. Raising the aging temperature from 500°C to 600°C transformed the α phases from fine acicular to coarse lamellar morphologies, reduced their quantity, decreases strength, and improves plasticity—elongation increased from 4.25 ± 2.5% to 15.5 ± 3.5%. This study is anticipated to provide valuable data and technical support for the engineering application of PBF‐LB‐fabricated Ti‐38644 alloy components in aerospace and related fields.