挤压态ZM61-Sn合金的显微组织及高温力学性能

Microstructures and elevated temperature mechanical properties of as-extruded ZM61-Sn alloys

摘要:

利用金相显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM)和高温拉伸对挤压态ZM61-xSn(x=2, 4, 8 wt. %)合金的显微组织，高温力学性能和断裂机制进行了研究。结果表明添加Sn 元素可有效细化合金组织且细化效果随Sn 含量的增加而增强。挤压态ZM61-xSn(x=2, 4, 8 wt. %)合金的平均晶粒尺寸分别为11, 8和4 μm。随 Sn 含量的增加，合金的力学性能先升高后降低。 在所有的实验合金中ZM61-4Sn合金的强度最高，当在180 ℃下进行拉伸实验时，其极限抗拉强度和屈服强度分别为216和173 MPa。合金的延伸率随Sn 含量的增加而增加，当拉伸温度为300 ℃时，ZM61-xSn(x=2, 4, 8wt. %)合金的延伸率分别为183.8%, 235.8% 和258.6%。ZM61-4Sn合金具有最好的强度和塑性的结合。试样最后的断裂主要由局部缩颈引起以及试样的主要断裂机制为显微孔洞的聚集。当在260和300 ℃下拉伸时，合金发生了不完全的动态再结晶。

Abstract:

Microstructures, elevated temperature mechanical properties and fracture mechanisms of the as-extruded ZM61-xSn (x=2, 4, 8, wt. %) alloys are investigated by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and high temperature tensile tests. The experimental results reveal that the addition of Sn can refine microstructures and the refinement effect increases with the increase of Sn content. The average grain size of the as-extruded ZM61-xSn (x=2, 4, 8 wt. %) alloys are 11, 8 and 4 μm, respectively. With increasing of Sn amount, the strength of experimental alloys increase at first and decrease afterward. ZM61-4Sn alloy shows the highest strength, which ultimate tensile strength and yield strength are 216 and 173 MPa tested at 180 ℃, respectively. The ductility increasing with the content of Sn increasing, the elongation of as-extruded ZM61-xSn (x=2, 4, 8 wt. %) alloys are 183.8%, 235.8% and 258.6%, respectively, when tensile temperature reaches 300 ℃. The ZM61-4Sn alloy has the optimal coalescent of strength and ductility. The localized necking leads the final fracture of the specimens and the micro-void coalescence is the main fracture mechanical. Incomplete dynamic recrystallization occurs when tensile tests are carried out at 260 and 300 ℃.