【摘要】 为了优化热轧工艺制造出高性能的铝合金，本文通过光学显微镜（OM）、扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和透射电子显微镜（TEM）等表征手段结合室温拉伸实验，研究了热轧温度对Al-Mg-Si-0.1La铝合金微观组织和力学性能的影响。结果表明，轧制温度对Al-MgSi-0.1La铝合金的大小角度晶界、再结晶组织分布、局部取向差以及位错密度有很大影响。轧制温度为350℃时，Al-Mg-Si-0.1La铝合金具有91.9%的小角度晶界、 3.3%的再结晶组织而且局部取向差和位错密度达到最大。随着轧制温度从350℃升高到500℃，T6态Al-Mg-Si-0.1La铝合金的晶粒尺寸逐渐增大，长径比呈现先增大后减小的趋势，在350℃获得了细小等轴晶，平均晶粒尺寸为58μm。低温轧制会使Al-Mg-Si-0.1La铝合金基体内部形成大量存储能，经过T6热处理后使晶粒显著细化；同时会使粗大第二相破碎减少，提高了基体内部的均匀性，有利于纳米级强化相析出。在350℃轧制及T6热处理后Al-Mg-Si-0.1La铝合金具有最佳的力学性能，其抗拉强度和延伸率分别为328 MPa和9.3%。更多还原

【Abstract】 Hot rolling process is very important; it will affect the microstructure and mechanical properties of hot rolled products. In order to optimize the hot rolling process to produce high performance aluminum alloy, this paper adopted the characterization methods of optical microscope(OM), scanning electron microscope(SEM), electron backscattering diffraction(EBSD), transmission electron microscope(TEM) and room temperature tensile experiment. The effect of hot rolling temperature on the microstructure and mechanical properties of Al-Mg-Si-0.1 La aluminum alloy was studied. The results showed that the rolling temperature had great influence on the grain boundaries, recrystallization structure distribution, local orientation difference and dislocation density of Al-Mg-Si-0.1 La aluminum alloy. With the increase of rolling temperature, the number of small angle grain boundaries of Al-Mg-Si-0.1 La aluminum alloy gradually decreased, and the maximum value was 91.9% at 350 ℃, and the minimum value was 88.6% at 500 ℃. When the rolling temperature was 350 ℃, a large number of deformation structures appeared in the matrix, and a small amount of recovery structures appeared, and the recrystallization structures were very few and almost invisible in the matrix. At 500 ℃, the recrystallization structures and recovery structures increased, while the deformation structures decreased. This was because when the deformation occurred at a lower temperature, the driving force of recrystallization was insufficient but the recovery process was sufficient, so a high-volume fraction subcrystalline structure characterized by a small angle grain boundary was formed. When the rolling temperature was increased, the thermal activation process of atoms was increased, the driving force of grain movement was increased, and the recrystallization process was promoted. The recrystallization grains had large Angle grain boundaries, so the proportion of large angle grain boundaries was increased, and the proportion of recrystallization fraction was increased. When rolling at 350 ℃, the difference of orientation between grain boundary and part of grain was large, which meant that the degree of plastic strain inside grain was large. When the rolling temperature rose to 400 ℃, the orientation difference within the grain tended to a fixed value, and the strain distribution became uniform. When the rolling temperature continued to rise, the orientation difference inside and at the grain boundary of some grains was very small. With the increase of rolling temperature, Kernel Average Misorientation(KAM) value showed a decreasing trend, indicating that lower rolling temperature would increase the geometric dislocation density. Because Al-Mg-Si aluminum alloy was heat-treatable aluminum alloy, it was treated by solution aging after hot rolling deformation treatment. The results showed that the average grain size of T6 Al-Mg-Si-0.1 La aluminum alloy increased gradually with the increase of rolling temperature, and the recovery process of Al-Mg-Si-0.1 La aluminum alloy was weak when rolling at 350 ℃, and high-density dislocation could be accumulated to store a lot of energy, which promoted the full recrystallization during the aging process. The average grain size was significantly reduced, and fine equiaxed crystals with a size of 58 μm were obtained at 350 ℃. A large amount of stored energy was formed in Al-Mg-Si-0.1 La aluminum alloy matrix by low temperature rolling, and the grains were refined significantly after T6 heat treatment. At 350 ℃ hot rolling, due to the low rolling temperature, the deformation resistance of the sample increased, and the coarse second phase was fully broken during the deformation process, and the size was reduced. When rolling at low temperature, the recovery process was inhibited, and a large number of dislocation proliferated to obtain a high density of dislocation defects, which ultimately led to a significant reduction of the coarse number after heat treatment, improved the uniformity of the matrix, and was conducive to nanoscale enhanced phase precipitation. After rolling at 350 ℃ and T6 heat treatment, Al-Mg-Si-0.1 La aluminum alloy had the best mechanical properties, its tensile strength and elongation were 328 MPa and 9.3%, respectively. In this study, it was found that the tensile strength of Al-Mg-Si-0.1 La aluminum alloy gradually decreased with the increase of rolling temperature. In order to explore the reasons for the different mechanical properties of the alloy, the influence of grain boundary strengthening on the mechanical properties was first considered. The strength provided by grain boundary strengthening could be calculated by Hall-Petch formula. With the decrease of rolling temperature, the average grain size of the alloy decreased significantly, the total grain boundary area increased, and the hindrance to the dislocation increased, resulting in the alloy strength increasing. Dislocation density was also one of the main factors affecting mechanical properties. It could be seen from the formula of dislocation strengthening that the dislocation density was proportional to the alloy strength, so the lower the rolling temperature, the greater the dislocation density and the greater the alloy strength.更多还原