Research On Microstructure,Texture And Mechanical Properties Of Al-Mg-Mn Alloy

Al-Mg-Mn alloy is a kind of alloy without heat treatment which has good strength, plasticity and toughness, and corrosion resistance. It is one metal materials which was widely used in production and life. Its comprehensive properties are closely related to the microstructure. The product performance of Al-Mg-Mn alloy was affected by the change of microstructure and orientation distribution during annealing process, thus, it is very important to research the microstructure and texture during annealing process.Al-5.5Mg-0.5Mn alloy was prepared by semi-continuous easting technique in this thesis. The microstructure and the effect of second phase on recrystallization were analyzed by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) and energy dispersive spectroscopy(EDS), electron back-scattered diffraction(EBSD), in which the recrystallization behavior was investigated by in situ TEM observation technique, the mechanical properties were investigated by hardness and tensile properties testing, also the misorientation angle distribution and texture in different annealing process was researched by EBSD, last the forming factors of texture were discussed.The testing results show that a number of Al6 Mn particles whose size were fine and dispersively distributed were found in the alloy sheet, which hinder the growth of recrystallization grain. The recrystallization temperature was defined by the results of microstructure and hardness, and the range from 250 to 325 ℃ ℃. The ideal annealing process of Al-5.5Mg-0.5Mn alloy is 325 ℃×1h, in which has the excellent comprehensive mechanical properties, yield strength reaches to 255 MPa, tensile strength reaches to 378 MPa, elongation rate reaches to 23.8%.It turned out that there are 89 percent of low-angle grain boundaries were found in the cold-rolling sheet, which decreased as the temperature increases in the annealing process, By contrast, the high-angle grain boundaries increased as the temperature increases, which can be up to 80.2 percent. The﹛1 1 2﹜﹤1 1 1﹥,S﹛1 2 3﹜﹤6 3 4﹥and﹛1 1 0﹜﹤1 1 2﹥are primary textures in Al-Mg-Mn alloy cold-rolling sheet. The annealing temperature is important factor which affects the texture, deformation texture decreased as the temperature increases, Meanwhile, the recrystallization texture increased as the temperature increases, During the recrystallization temperature range, the cube texture become the predominant, the copper and S texture gradually disappeared, and a small amount of brass textures was retained.