Cao Furong, Shang Huihui, Guo Nanpan, Kong Shuting, Liu Renjie
School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China.
State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China.
Materials (Basel). 2022 Oct 27;15(21):7539. doi: 10.3390/ma15217539.
To explore new approaches to severe plastic deformation and the ductility of a multicomponent magnesium-lithium alloy, an ultralight microduplex Mg-9.55Li-2.92Al-0.027Y-0.026Mn alloy was made by novel multidirectional forging and asymmetrical rolling, and the superplasticity behavior was investigated by optical microscope, hot tensile test, and modeling. The average grain size is 1.9 μm in this alloy after multidirectional forging and asymmetrical rolling. Remarkable grain refinement caused by such a forming, which turns the as-cast grain size of 144.68 μm into the as-rolled grain size of 1.9 μm, is achieved. The elongation to failure of 228.05% is obtained at 523 K and 1 × 10 s, which demonstrates the high strain rate quasi-superplasticity. The maximum elongation to failure of 287.12% was achieved in this alloy at 573 K and 5 × 10 s. It was found that strain-induced grain coarsening at 523 K is much weaker than the strain-induced grain coarsening at 573 K. Thus, the ductility of 228.05% is suitable for application in high strain rate superplastic forming. The stress exponent of 3 and the average activation energy for deformation of 50.06 kJ/mol indicate that the rate-controlling deformation mechanism is dislocation-glide controlled by pipe diffusion.
为探索多组分镁锂合金严重塑性变形及延展性的新方法，通过新型多向锻造和非对称轧制制备了一种超轻微双相Mg-9.55Li-2.92Al-0.027Y-0.026Mn合金，并采用光学显微镜、热拉伸试验和建模研究了其超塑性行为。经过多向锻造和非对称轧制后，该合金的平均晶粒尺寸为1.9μm。这种成形方式使铸态晶粒尺寸由144.68μm细化为轧制态晶粒尺寸1.9μm，实现了显著的晶粒细化。在523K和1×10s时获得了228.05%的断裂伸长率，这表明了高应变速率准超塑性。该合金在573K和5×10s时实现了287.12%的最大断裂伸长率。研究发现，523K时的应变诱导晶粒粗化比573K时的应变诱导晶粒粗化弱得多。因此，228.05%的延展性适用于高应变速率超塑性成形。应力指数为3，平均变形激活能为50.06kJ/mol，表明速率控制变形机制是由管道扩散控制的位错滑移。
