Influence Of Rolling And Heat Treatment On The Microstructure And Property Of LA83-Y Mg-Li Alloy

This study is focus on the effects of homogenization process, hot rolling, cold rolling and heat treatment on the microstructure and mechanical properties of LA83-Y alloy with the help of inductively coupled plasma atomic emission spectroscopy (ICP), Optical metallographic microscopy (OM), Scanning electron microscopy (SEM), X-ray diffraction technique (XRD), Electronic Tensile Tester and Vickers hardness tester. The evolution of microstructure and mechanical properties during different processes are observed and analyzed. The main results are as follow:(1) There exists five phases in LA83-Y alloy:α, β, A12Y, AlLi and MgAlLi2, and a phase has two shapes:irregular block and long strip. After annealed, a phase is spheroidized, and becomes growth with a long of time. Finally, the microstructure and composition become homogeneous. So it can be determined that annealing at300℃for12h is the optimum homogenization process for LA83-Y alloy.(2) a phase of the alloy becomes longer along the rolling direction with an obvious fiber structure after rolled at280℃. The strength and hardness of the alloy increases gradually with the increasing of the amount of the reduction, and the change of the plasticity is opposite. The ultimate tensile strength, elongation and Vickers hardness of the hot rolled sheet with a total reduction rate of0.8is195.75MPa、18%、74.84, respectively. Its tensile fracture mode at room temperature is quasi-cleavage fracture.(3) The hot rolled sheet is rolled at room temperature after annealing treatment. The edge of the cold rolled sheet has no crack when the reduction rate is0.5. a phase becomes longer along the direction of rolling with a characteristic of a strong fiber structure. The ultimate tensile strength, elongation and Vickers hardness of the cold rolled sheet with a total reduction rate of0.5is265.67MPa、11%、86.06, respectively. Its tensile fracture mode at room temperature is cleavage fracture.(4) After annealing the cold rolled sheet, most thin fibrous a phase is parted to form many spherical a phase and the coarse a phase also forms a clear bamboo-like structure. The ultimate tensile strength, elongation and Vickers hardness of the alloy of this state are184.12MPa、35%、65.91respectively. Its tensile fracture mode at room temperature is dimple fracture.(5) The texture types of the alloy with different treat processes are investigated. After rolled at280℃, the textures of a phase are (0001) basal texture and prismatic texture. However, the textures of β phase are {112}<110> texture,{112}<111> texture and {001} cubic texture. When the annealed sheet is rolled at room temperature, the textures of a phase are (0001) basal texture,{1120},{0110} prismatic texture and{1121}<1122> texture. The textures of β phase are {112}<110> texture,{112}<111> texture and {001} cubic texture. When the cold rolled sheet is annealed at350℃with a time of60min, the textures of a phase are (0001) basal texture and{1120},{0110} prismatic texture. Nevertheless, the textures of β phase are{112}<110> texture,{112}<111> and{001} cubic texture.