Development of a novel heat treatment in L-PBF fabricated high strength A205 Al alloy: Impact on microstructure-mechanical properties

Abstract

Recent advances in the additive manufacturing of high-strength aluminium alloys have enabled the replacement of cast components in the aerospace and automotive sectors. However, a major challenge facing additively manufactured alloys is the lack of standardised heat treatments (HT) to optimise mechanical properties. This study investigates the development of a novel Rapid HT and its influence on the microstructure and mechanical properties of the A205 aluminium alloy (A20X™) fabricated by Laser-Powder Bed Fusion (L-PBF). The alloy was subjected to three HTs: Standard T7 HT, Commercial HT, and Rapid HT. Microstructural analysis, using Scanning electron microscopy (SEM) and Electron backscatter diffraction (EBSD), revealed a finer grain size for Commercial HT and Rapid HT, with average grain sizes of 2.4 μm and 2.3 μm, respectively, compared to the average 3.2 μm of the Standard T7. STEM analysis revealed a higher volume fraction and finer Ω-AlCuAgMg and ϑ'-Al₂Cu precipitates in the Rapid HT compared to the other HTs. Mechanical tests highlighted superior performance for the Rapid HT, achieving a UTS of 465 MPa, compared to the values of 422 MPa and 449 MPa for Standard T7 HT and Commercial HT, respectively. Additionally, the Rapid HT showed an increase in fatigue life of around 189 % and 125 % and in creep life of around 33 % and 80 % compared to Standard T7 HT and Commercial HT, respectively. These findings highlight the novelty of the Rapid HT in refining microstructure and enhancing mechanical properties beyond conventional HTs, paving the way for more efficient and sustainable HT strategies for L-PBF manufactured high-strength Al alloys.