球化温度对AZ91HP镁合金显微组织及力学性能的影响

Influence of Spheroidizing Temperature on Microstructure and Mechanical Properties of AZ91HP Magnesium Alloys

通过场发射扫描电子显微镜及能谱分析、光学显微镜、X射线衍射分析、室温拉伸试验及布氏硬度测试等手段研究了球化温度对AZ91HP镁合金显微组织和力学性能的影响。结果表明,退火处理后,铸态AZ91HP合金组织中粗大离散的共晶相消失,在其后的随炉缓冷过程中以层片状形式弥散,均匀分布于α-Mg基体;球化过程中,层片状β-Mg_(17)_Al_(12)相自身溶断;球化温度在300℃时球化效果最好;硬度值随球化温度的升高先缓慢上升后下降,且高于铸态合金;经300℃保温20 h球化处理后,合金的抗拉强度、屈服强度达到最大值242.7、132.6 MPa,分别比铸态合金提高了21.78%、28.86%,伸长率较铸态提高了57.47%。

Effect of spheroidizing temperature on microstructure and mechanical properties of as-cast AZ91HP magnesium alloy were investigated by means of field emission scanning electron microscopy （FESEM） and EDS, optical microcope, XRD analysis, tensile tests and hardness tests. The results show that the coarse divorced eutectic phase of AZ91HP cast magnesium alloy disappears after annealing treatment, and in the sequent furnace cooling process lamellar phase precipitates, which uniformly distributes in the α-Mg matrix; in the spheroidizing process, lamellar β-Mg17Al12 phase dissolves and breaks; the spheroidizing effect of the spheroidizing temperature at 300 ℃ is the best; the hardness value increases firstly slowly and then decreases with the increase of the spheroidizing temperature, and is higher than that of the as-cast alloy; after spheroidizing treatment at 300 ℃ for 20 h, the tensile strength and yield strength of the alloy reach the maximum value of 242.7 MPa and 132.6 MPa respectively, which are increase by 21.78% and 28.86%, and the elongation is increased by 57.47% compared with that of the as-cast alloy.