Nd对Mg-13Gd-0.5Zr合金组织和力学性能的影响

Effect of Nd on Microstructure and Mechanical Properties of Mg-13Gd-0.5Zr Alloy

采用X射线衍射仪、光学显微镜、扫描电镜、能谱仪和电子拉伸试验机等设备研究了Nd对Mg-13Gd-0.5Zr合金组织和力学性能的影响,结合错配度理论、位错密度的变化规律讨论了合金晶粒细化的机理,并从细晶强化和析出强化等方面阐述了合金强化机制。研究发现Mg-13Gd-0.5Zr合金的组成相主要有α-Mg、Mg5Gd,Nd的加入在合金中形成了新相Mg41Nd5,并细化了合金晶粒。Nd的加入显著提高了Mg-13Gd-0.5Zr合金的室温和高温力学性能,当Nd的添加量为2%(质量分数)时,合金在室温和高温下的力学性能达到最大值279MPa(室温)、319MPa(250℃),合金力学性能的提高主要归因于Mg5Gd和Mg41Nd5相的析出强化和细晶强化的双重效果。Mg-13Gd-2Nd-0.5Zr合金在不同温度下的断裂方式主要以脆性断裂为主,随着拉伸温度的升高由脆性断裂向韧性断裂转变。

The effects of Nd on the microstructure and mechanical properties of Mg-13 Gd-0.5 Zr alloy were studied by X-ray diffraction, optical microscope, scanning electron microscope, energy dispersive spectrometer and electronic tensile testing machine. The mechanism of grain refinement was discussed based on the mismatch theory and the change rule of dislocation density. The strengthening mechanism was also discussed from fine-grained strengthening and precipitation strengthening. The results show that the main constituent phases of Mg-13 Gd-0.5 Zr alloy are α-Mg and Mg5 Gd. The addition of Nd forms a new phase Mg41 Nd5 in the alloy and refines the grain of the alloy. The addition of Nd significantly improves the mechanical properties of Mg-13 Gd-0.5 Zr alloy at room temperature and high temperature. When the addition of Nd is 2 wt%, the mechanical properties of the alloy reach the maximum values of 279 MPa(room temperature) and 319 MPa(250 °C). The improvement of mechanical properties of the alloy is mainly attributed to the dual effects of precipitation strengthening and fine grain strengthening of Mg5 Gd and Mg41 Nd5 phases. Brittle fracture is the main fracture mode of Mg-13 Gd-2 Nd-0.5 Zr alloy at different temperatures. As the stretching temperature increases, the alloy changes from brittle fracture to ductile fracture.