The Deformation Behavior Of Mg-Li And Mg-Li-Zn-Y Alloy After Hot Rolling And Annealing Treatment

The tensile test was executed on Mg-4Li alloy, Mg-6Li and Mg-4Li-6Zn-Y alloy which was annealed after hot rolled in different directions and at different rates, analyzing the microstructure with the characterization method of OM and SEM, the paper studies the mechanical behavior and strain rate effect of the three kinds of alloy systematically.The experiment results are summarized as follows:Dynamic recrystallization occurs in Mg-4Li alloy, Mg-6Li alloy and Mg-4Li-6Zn-1Y alloy after hot rolling at 270 ?, and the recrystallization is more obvious in Mg-4Li-6Zn-1Y alloy after rolling at 320 ?. The second phases of Mg-4Li-6 Zn-Y alloy are I phase, W phase and Mg0.97Zn0.03 phase.The results shows that the strength of Mg-4Li alloy in rolling direction is higher than the perpendicular rolling direction after stretching in different directions, and the strength in the rolling direction can reach 168.8MPa. But the ductility of Mg-4Li alloy in rolling direction is less than that in perpendicular rolling direction. The phenomenon of Mg-6Li alloy streched in different directions is identified with that of Mg-4Li alloy, and the maximum strength of Mg-6Li alloy in the rolling direction can reach 153.8MPa because of ?-phase. Adding Zn and Y element to the Mg-4Li alloy can significantly improve the strength. The tensile strength of the Mg-4Li alloy in the rolling direction can reach 267.1MPa after rolling at 270?,while the tensile strength decreased slightly after rolling at 320 ? and the maximum of tensile strength in rolling direction is 262 MPa.The PLC occurs obviously at 1×10-3-1×10-2s-1 in rolling direction and 1×10-4-1×10-2s-1section in perpendicular rolling direction of Mg-4Li alloy. With the strain rate increasing, the PLC is weakened. The PLC only occurs at 1×10-4s-1 when the Mg-6Li alloy is stretched in different directions. The PLC occurs in Mg-4Li-6Zn-1Y alloy rolled at 270 ? at 1×10-2s-1 and Mg-4Li-6Zn-1Y alloy rolled at 320 ? at 1×10-3-1×10-2s-1.The complete recrystallization of Mg-4Li alloy occurs after annealing at 240?,and theaverage grain size is about 38?m and the maximum of tensile strength is 149 MPa. The recrystallization of Mg-6Li alloy occurs after annealing at 200?, and the average grain size of ? phase is about 25?m and the maximum of tensile strength is 147.3MPa. The twins of Mg-4Li-6Zn-1Y alloy after hot rolling is eliminated basically and the ratio of recrystallization increases after annealing at 260?.