Mg-Li-Zn-RE alloy hot deformation behavior

Title: Mg-Li-Zn-RE alloy hot deformation behavior of
　　Author: Li Zhiqiang
　　Degree-granting units: Harbin Engineering University
　　Keywords: Mg-Li alloy;; hot deformation;; constitutive equation;; thermal processing graph;; dynamic recrystallization
　　Summary:
　　Experimental studies using thermal compression-extruded Mg-Li-Zn-RE alloy hot deformation behavior. Analysis of the variation of flow stress of the alloy, respectively, with power functions, exponential and hyperbolic sine function to establish the Neodymium magnets thermal deformation of alloy flow stress constitutive equation, the alloy hot-drawing process maps, analysis of the alloy after hot deformation of the organization evolution characteristics.
　　Experiment by the α-Mg alloy phase, β-Li phase and phase composition of rare earth compounds. After extrusion, the alloy phase are along the deformation direction of the flow line was distributed, β phase has completely dynamic recrystallization, α-phase dynamic recrystallization did not occur, mainly in the rare-earth compounds with α / β and β phase at the phase interface . Experimental alloy high strength at room temperature (σ0.2 = 256MPa, σb = 260MPa), elongation δ = 14%.
　　Alloy flow stress curves show the characteristics of dynamic recrystallization. Use of power function and exponential function fitting error larger flow stress equation, and the hyperbolic sine function can better describe the thermal deformation behavior of alloys. Alloy the stress exponent n increases with increasing temperature, the deformation mechanism of dislocation climb. Higher average thermal deformation activation energy (about 148kJ/mol), hot deformation activation energy with temperature and strain rate increase with the increase, but when the strain rate of ε = 10s-1, the hot deformation activation energy and the strain rate ε = 0.01s-1, agreed.
　　Figure shows the thermal processing thermal processing performance alloy under the experimental conditions are good, there are three peak efficiency region, the rheological instability region found no cracks, holes, and other instability phenomena with rheological instability there. Optimal parameters of thermal processing of the alloy is 250 ℃ / 10s-1 and 250 ℃ / 0.001s-1.
　　Experimental alloys in the β-phase in all the deformation conditions are dynamic recrystallization occurs rapidly, α-phase dynamic recrystallization http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php increases with strain rate and temperature reduction is not adequately carried out, recrystallized grains in the rare-earth phase, α / β phase interface, the formation of grain boundaries, etc.. Grain size decreases with strain rate and temperature increases, but the temperature at 400-450 ℃ average grain size of α phase but decreases with increasing temperature. And α-phase of rare earth β-phase of the promotion of dynamic recrystallization, and dynamic recrystallization of α-phase was inhibited.
　　Degree Year: 2010