Effect of Heat Treatment on the Microstructural Characteristics and Mechanical Properties of Al-Zn-Mg-Cu-Sc Alloy Prepared via Wire-Arc Directed Energy Deposition Process
Received date: 2025-02-24
Revised date: 2025-05-19
Online published: 2025-06-25
Supported by
Central Government Guides Local Funds for Science and Technology Development(YDZJSX20231A045);Central Government Guides Local Funds for Science and Technology Development(YDZJSX2024D053);Start-up Fund for Scientific Research of Taiyuan University of Science and Technology(20-232074);Start-up Fund for Scientific Research of Taiyuan University of Science and Technology(20212011);Start-up Fund for Scientific Research of Taiyuan University of Science and Technology(20222063);Natural Science Foundation of Shanxi Province(202303021212216)
Wire-arc directed energy deposition (DED) shows considerable potential for fabricating structural components from Al-Zn-Mg-Cu-Sc alloys. However, its layer-by-layer deposition nature leads to continuous grain boundary second-phase networks, grain coarsening, elemental microsegregation, and residual stress accumulation during solidification of 7075-Sc aluminum alloys, significantly compromising their mechanical properties and industrial viability. As a precipitation-strengthened alloy, 7075 can be optimized through heat treatment to control the morphology and distribution of secondary phases, thereby improving mechanical performance. Nevertheless, the inhomogeneous as-deposited microstructure proves difficult to fully homogenize using conventional heat treatment, necessitating precise temperature control and tailored aging schedules for effective thermal processing. In this study, crack-free, thick-walled Al-Zn-Mg-Cu-Sc alloy components were fabricated using custom 7075-Sc welding wire and the cold metal transfer process. Microstructural analysis revealed that the as-deposited alloy consists of fine equiaxed grains with an average diameter of approximately 14 μm and a continuous grain boundary second-phase distribution. Solution treatment at 470 oC results in a markedly reduced dissolution rate of the secondary phases over time, with a 4 h duration identified as optimal. Under this condition, 70.2% of the secondary phases are dissolved; the remaining phases are predominantly Al7Cu2Fe and Al2Mg3Zn3. Subsequent artificial aging at 120 oC showed that an aging time of 18 h yields optimal mechanical properties. Following the combined solution and aging treatments, the alloy exhibited a yield strength of 475.2 MPa, tensile strength of 542.1 MPa, and elongation of 5.2%. These values represent increases of 52.8%, 36.5%, and 36.8%, respectively, compared to the as-deposited alloy.
QIN Fengming , LI Yafei , LI Yajie , ZHAO Xiaodong , LIANG Shangshang , CHEN Jinqiu . Effect of Heat Treatment on the Microstructural Characteristics and Mechanical Properties of Al-Zn-Mg-Cu-Sc Alloy Prepared via Wire-Arc Directed Energy Deposition Process[J]. Acta Metall Sin, 2025 , 61(10) : 1542 -1554 . DOI: 10.11900/0412.1961.2025.00048
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