摘要
The effect of Gd content ranging from 6.5 wt.%to 8.5 wt.%on microstructure evolution and dynamic mechanical behavior of Mg−xGd−3Y−0.5Zr alloys was investigated by optical microscopy,X-ray diffraction,scanning electron microscopy and split Hopkinson pressure bar.The microstructure of as-cast Mg−xGd−3Y−0.5Zr alloys indicates that the addition of Gd can promote grain refinement in the casting.Due to the rapid cooling rate during solidification,a large amount of non-equilibrium eutectic phase Mg_(24)(Gd,Y)_(5) appears at the grain boundary of as-cast Mg−xGd−3Y−0.5Zr alloys.After solution treatment at 520℃ for 6 h,the Mg_(24)(Gd,Y)_(5) phase dissolves into the matrix,and the rare earth hydrides(REH)phase appears.The stress−strain curves validate that the solution-treated Mg−xGd−3Y−0.5Zr alloys with optimal Gd contents maintain excellent dynamic properties at different strain rates.It was concluded that the variation of Gd content and the agglomeration of residual REH particles and dynamically precipitated fine particles are key factors affecting dynamic mechanical properties of Mg−xGd−3Y−0.5Zr alloys.
采用金相显微镜、X射线衍射、扫描电子显微镜、分离式霍普金森压杆等手段,研究Gd含量(6.5%~8.5%,质量分数)对Mg-xGd-3Y-0.5Zr合金显微组织与动力学行为的影响。观察铸态Mg-xGd-3Y-0.5Zr合金显微组织可知,Gd的加入可促进晶粒细化。由于合金凝固时冷却速度快,在晶界处出现大量非平衡共晶相Mg_(24)(Gd,Y)_(5)。经过520℃固溶处理6h后,非平衡共晶相Mg_(24)(Gd,Y)_(5)融入基体中并产生稀土氢化物相(REH)。根据应力-应变曲线可知,不同Gd含量的固溶态Mg-xGd-3Y-0.5Zr合金在不同应变速率下均表现出优异的抗冲击性能。结果表明,Gd含量的变化、稀土氢化物粒子的聚集以及细小的动态析出相是影响Mg-xGd-3Y-0.5 Zr合金动态力学性能的关键因素。
基金
supported by the National Natural Science Foundation of China (Nos.51575289,51705270)
the Key Research and Development Project of Shandong Province,China (No.2019GHY112068)
the Natural Science Foundation of Shandong Province,China (No.ZR2019PEE028)。