挤压速度对NZ30K镁合金组织与力学性能的影响

Effect of extrusion speed on microstructure and mechanical properties of NZ30K magnesium alloy

研究了不同挤压速度挤压出的Mg-3.0Nd-0.2Zn-0.4Zr(质量分数,%,NZ30K)镁合金显微组织和室温力学性能。采用光学显微镜观察了合金的显微组织,采用材料拉伸试验测试了合金的室温力学性能,并利用扫描电子显微镜观察了拉伸试样的断口形貌和断口附近的显微组织。结果表明:当挤压速度相对较低时,发生部分再结晶,组织不均匀,合金的强度很高,而塑性则较差;当挤压速度较高时,合金发生了完全动态再结晶,组织均匀,再结晶晶粒明显长大,合金强度降低,而伸长率则明显提高。合理控制挤压速度可获得细小均匀的组织和良好的综合力学性能。

Microstructure and room-temperature mechanical properties of a Mg-3.0Nd-0.2Zn-0.4Zr （mass fraction, %, NZ30K） magnesium alloy extruded with different extrusion speeds were studied. The microstrueture of the alloy was observed by optical microscopy （OM） , the mechanical properties of the alloy at room temperature were examined by tensile test, the fracture morphology and the microstructure near fracture surface were observed by scanning electron microscopy （ SEM）. The results indicate that partially dynamic recrystallization occurs and the microstructure is inhomogeneous when the extrusion speed is relatively low. Moreover, the alloy exhibits high strength but low ductility. In contrast, when the extrusion speed is high, the alloy is subjected to completely dynamic recrystallization, the microstrueture is homogeneous and the recrystallized grains grow apparently. The strength of the alloy under high extrusion speed declines but the elongation is improved significantly. Fine and homogeneous microstructure and good mechanical properties can be obtained by controlling the extrusion speed during extruaion processing.