Research Of Flow Stress Behavior And Heat Treatment Of High Purity Al-Cu-Mg Alloy

The high purity Al-Cu-Mg alloy has the advantages of high-purity, high strength and high toughness. It developed by reducing the content of impurities such as Fe, Si and raising the proportion of Cu which is based on2024aluminum alloy. The phase constituents and composition distribution of the as-cast and homogenized high purity Al-Cu-Mg alloy were studied by OM, SEM and TEM. Establised the flow stress constitutive equations and the processing map, analysed the microstructure under different deformation conditions. And the machanical properties of alloy after thermomechanical treatment were studied. The conclusion can be summarized as follows:(1) Severe dendritic segregation exists in high purity Al-Cu-Mg alloy ingot, and Cu, Mg and Mn elements are uneven distributed from grain boundary to inside.(2) With increasing the homogenization temperature or prolonging the holding time, the residual phases are dissolved into the matrix gradually, grain boundaries become sparse and the distribution of all the elements beeomes more homogenized. The suitable homogenization treatment of high purity Al-Cu-Mg alloy is530℃for18h, which is consistent with the results of homogenizing kinetic analysis.(3) The flow stress behavior of high purity Al-Cu-Mg alloy during high temperature compression can be described by using the equation with Zener-Hollomon parameter. The four characteristic constants of materials are obtained as follows:A=1.95891×1014s-1, α=0.0118Mpa-1, n=5.59603, Q=216.647KJ/mol.(4) When the deformation temperature is below400℃, the hot deformation structure is mainly dynamic recovery structure:sub-grain structure. As deformation temperature is higher than400℃, dynamic recrystallization occurred in the alloy. The nucleation mechanism of recrystallizing process is subgrain coalescence and subgrain growth.(5) High purity Al-Cu-Mg alloy processing map was established by Dynamic material model(DMM), and the results show that the feasible region are:high strain rate (>0.5s’’) or450℃-500℃and0.01s-1～0.02s-1.(6) The cold-rolled state sheet of High purity Al-Cu-Mg alloy immediately be cold deformed of0%,5%,15%,20%,25%after solid solution treatment by500℃/1h, then ageing at195℃. And The age-hardening curve shows two stages ageing process. The pre-deformation improve age hardening characteristics of high purity Al-Cu-Mg alloy and accelerate the the alloy aging process, shorten the peak aging time. The age-hardening curve of high purity Al-Cu-Mg alloy sheet at the thermomechanical treatment shows two stages ageing process. And the pre-deformation improve age hardening characteristics of and accelerate the the alloy aging process, shorten the peak aging time. The strength of the alloy increases with the increase in the amount of deformation, while the elongation decreased with it. And deformation of15%shows the excellent comprehensive mechanical properties:σb of463.2MPa, σ0.2of414.2MPa and the elongation of8.5%...