热输入对 7N01 铝合金 MIG 焊热影响区微观组织与力学性能的影响

In order to investigate the influence of heat input on the microstructure and properties of the heat-affected zone in 7N01 aluminum alloy, T-joint specimens were prepared using gas metal arc welding under three different heat inputs of 0.35 kJ/mm, 0.49 kJ/mm and 0.63 kJ/mm. The microstructural evolution and micromechanical properties of the heat-affected zone were analyzed through transmission electron microscopy, electron backscatter diffraction, micro-tensile testing and microhardness testing. The results show that, reducing the welding heat input is an effective means of suppressing the softening phenomenon in the weld heat-affected zone of the 7N01 aluminum alloy, thereby enhancing its micro-mechanical properties. When the welding heat input is reduced from 0.63 kJ/mm to 0.35 kJ/mm, the micro-hardness of the heat-affected zone increases from 85HV to 95HV (increased by 11.7%), the micro-tensile strength increases from 239.7 MPa to 281.6 MPa (increased by 17.5%). The softened zone of the heat-affected zone improves by controlling the welding heat input, because the lower heat input can suppress the dissolution and coarsening of nano-sized η′(MgZn₂) strengthening phases and grain growth, while also refine the deformed microstructure. This collectively leads to the strengthening of the softened zone.