Zn含量对Mg-Mn-Zn合金显微组织和力学性能的影响

Microstructure and Mechanical Properties of Mg-Mn-Zn Magnesium Alloy with Different Zn Contents

通过添加少量的Zn元素制备了(%,质量分数)Mg-2.0Mn-x Zn(x=0,0.5,1.0,1.5,2.0)合金。对合金进行挤压变形,并利用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)等手段,研究了少量的Zn元素对Mg-Mn合金组织及力学性能的影响。实验结果表明,Mg-2.0Mn-x Zn合金的铸态及挤压态组织中主要含有的第二相为颗粒状的α-Mn相,Zn元素均匀固溶于Mg基体中。少量添加的Zn元素可以显著细化铸态Mg-Mn-Zn镁合金的晶粒尺寸。随着Zn含量增加,挤压态合金中动态再结晶区域增加,混晶组织呈减少趋势。少量添加Zn元素对挤压态Mg-2.0Mn合金的强度及塑性都有明显的改善作用,尤其是合金的屈服强度最高增加42%,延伸率增加57%。随着Zn添加量增加,合金强度的增加趋势减弱。SEM观察显示挤压态Mg-2.0Mn-x Zn合金拉伸试样的断口形貌以韧窝及解理台阶为主,呈现韧性断裂与准解理断裂的混合断口形貌。

Mg-2.0Mn-xZn （ x = 0, 0.5, 1.0, 1.5, ：2.0） （ %, mass fraction） alloys were fabricated by adding a small amount of Zn into Mg-2.0% Mn alloys under conventional solidification. After hot extrusion deformation, the effects of small amount of Zn on the mi- crostructure and mechanical property of Mg-2.0Mn-xZn alloy were investigated by optical microscope（OM） , scanning electron micro- scope （SEM） and energy dispersion spectrometer（EDS）. In the as-cast state and as-extruded state, the main second phase was oL-Mn particle and Zn was dissolved in the matrix. A small addition of Zn had significant refining effect on the grain size of as-cast alloy. In the as-extruded alloy, the area of dynamic recrystallization increased and the mixed grain structure had a downward tendency with the increase of Zn addition. The strength and plasticity of extruded Mg-Mn-Zn alloy significantly improved with a small addition of Zn, the yield strength increased up to 42% and the elongation increased up to 57%. The improvement of strength diminished with the increase of Zn addition. The fracture morphology of extruded Mg-2.0Mn-xZn alloy mainly consisted of dimples and cleavage steps presented a mixed fracture morphology of ductile fracture and quasicleavage fracture.