Si添加对快速凝固/粉末冶金镁合金组织及力学性能的影响

采用快速凝固/粉末冶金工艺分别制备Mg-8Al-0.5Zn-0.15Mn及Mg-8Al-0.5Zn-0.15Mn-2Si合金挤压棒材。利用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)及拉伸机,研究了Si添加对Mg-Al-Zn-Mn合金显微组织及室温力学性能的影响。结果表明,与热压Mg-Al-Zn-Mn合金相比,热压Mg-Al-Zn-Mn-Si合金内晶界上网状分布的Mg17Al12相减少,晶内出现多边形状Mg2Si相。热压后的反向挤压过程中Mg-Al-Zn-Mn合金与Mg-Al-Zn-Mn-Si合金组织均发生连续动态再结晶,其中Mg-Al-Zn-Mn-Si晶粒细化较好,伸长率较大,第二相Mg2Si与基体接合良好,但Mg2Si相周围出现的应力集中导致屈服强度和抗拉强度降低。随着反向挤压温度上升,反向挤压制备的两种合金屈服强度和抗拉强度均降低,而伸长率增大。

Effect of Si Addition on Microstructure and Mechanical Properties of Mg-Al-Zn-Mn Alloy Fabricated by Rapidly solidified powder metallurgy

Mg-8Al-0.5Zn-0.15Mn and Mg-8Al-0.5Zn-0.15Mn-2Si extruded bars were prepared by Rapidly solidified powder metallurgy process. The effects of Si addition on the microstructure and mechanical properties of Mg-Al-Zn-Mn alloy were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffractometry and stretching machine. The results show that compared with the hot-pressed Mg-Al-Zn-Mn alloy, the Mg17Al12 phase in the grain boundary of the hot-pressed Mg-Al-Zn-Mn-Si alloy decreases, and the polygonal Mg2Si phase appears in the crystal. During the reverse extrusion process, the two hot-pressed alloys undergo continuous dynamic recrystallization. Mg-Al-Zn-Mn-Si has fine crystal grains and large elongation, and the second phase Mg2Si is well bonded to the matrix. Stress concentration is likely to occur around the Mg2Si during stretching, which becomes the starting point of the crack, thereby lowering the yield strength and tensile strength. As the reverse extrusion temperature rises, both the yield strength and the tensile strength of the two alloys decrease, while the elongation increases.