Microstructure Evolution and Prediction Model of 6082-T6 Aluminum Alloy Pulsed Metal Inert Gas Welded Joint

The weld metal (WM) and heat-affected zone are often the weak areas of aluminum alloy welded joints, in which poor properties of WM are typically associated with the microstructure formed during the melting and solidification. This paper focuses on the changes in microstructure and properties of aluminum alloy WM. Based on the finite element method, a three-dimensional model for predicting the columnar-to-equiaxed transition (CET) of weld metal during pulsed metal inert gas welding of 6082-T6 aluminum alloy was successfully established.At the same time, this study also analyzed the changes of microstructure and mechanical properties of WM under different heat inputs. The criterion curve for the CET of 6082-T6 aluminum alloy WM was expressed as \(G^{n} /R = C_{st}\) $G^n/R=C_{\mathit{st}}$ , where \(n\) $n$ is 7.85855, and \(C_{st}\) $C_{\mathit{st}}$ is 7.9749 × 10⁴. Additionally, it is found that as the heat input increases, the grain size of WM initially decreases and then increases, and promoting the formation of equiaxed grains. At the same time, the content of Mg₂Si and Al₆ (Mn, Fe) phases in the WM increases, which affects the microhardness of the WM . This method is also applicable to other aluminum alloys joints, and it is of significant importance in predicting microstructure transformation of aluminum alloys WM.