Effect of homogenization heat treatment on refractory phase and grain size of 5083 aluminum alloy

In order to study the changes in the content, type of the refractory phases and grain size during homogenization of the 5083 aluminum alloy, material microstructure was characterized by metallographic microscope (OM), scanning electron microscope(SEM), energy dispersive spectrometer(EDS), differential scanning calorimetry (DSC) and X-ray diffractometer (XRD). The results show that the refractory phases in the cast 5083 aluminum alloy are composed of Al(FeMnCr) phases, Al(FeMnCr)Si phases and Mg2Si phases. The composition of the cast state alloy was verified by using phase diagram calculations, and the results are basically consistent with the experiment. As the temperature rises from 460 ℃ to 560 ℃, the electrical conductivity increases firstly and then decreases. This is related to the precipitation of dispersed phase and the dissolution of refractory phase in the structure. When the homogenization processing is 540 ℃/10 h and 560 ℃/10 h, the refractory phase is dominated by the needle-flake Al(FeMnCr) phases, Mg2Si phases is fully solubilized, the area fractions are 0.730% and 0.632%, respectively, and there is no over burned tissue at the same time, and there are obvious dispersed phase particles in the grain. Therefore, to dissolve part of the refractory phases in cast 5083 aluminum alloy, the homogenization temperature must be ≥540 ℃. Increasing homogenization temperature and prolonging homogenization time will increase grain size.When the homogenization temperature is less than 540 ℃, the insoluble phase changes have little effect on the grain growth, when the homogenization temperature is greater than 540 ℃, the average grain size begins to be greater than 140 μm, and the refractory phase is dissolved at the same time.