Mg-4Y-2.5Nd-0.6Zr合金微观组织及力学特性的研究

Microstructure and mechanical properties of Mg-4Y-2.5Nd-0.6Zr alloy

利用光学显微镜、XRD衍射分析仪、扫描电子显微镜、透射电子显微镜、万能拉伸试验机等仪器设备研究了Mg-4Y-2.5Nd-0.6Zr合金铸态、固溶态和峰时效态的微观组织、室温和高温力学特性及断裂行为。结果表明:合金的铸态组织主要由α-Mg、Mg41Nd5和Mg24Y5组成;经固溶处理,共晶组织完全溶入基体,仅残余方块相Mg24Y5;再经时效处理,晶内弥散析出大量β″和β′相,有效强化了合金,对应的室温抗拉强度、屈服强度和伸长率分别为292、215 MPa和4%;随着拉伸温度的提高,峰时效态合金的强度逐渐降低、伸长率逐渐增加,室温断裂类型为解理断裂,而250℃的断裂方式表现为准解理断裂。

Microstructures, mechanical properties and fracture behaviors of Mg-4Y-2.5Nd-0.6Zr alloy at different states were investigated by Optical Microscope （OM）, X-ray Diffractometer （XRD）, Scanning Electron Microscope （SEM）, Transmission Electron Microscope （TEM） and universal tensile test machine. Results show that the as-cast sample mainly consists of α-Mg matrix, Mg41Nd5 phase and Mg24Y5 particle. After solution treatment, the eutectic compounds completely dissolve into the matri. with a few cuboid- shaped particles remained. After subsequent ageing, a great number of dispersed β＂and β＇ precipitates distribute throughout the matrix, which strengthens the alloy, corresponding to mechanical properties as follows：σb=292 MPa, σ0.2= 215 MPa and δ=4%. Besides, the strength of peak-aged sample decreases gradually with a gradual increase of ductility. The peak- aged sample exhibits cleavage fracture mode at room temperature, and the sample shows a quasi-cleavage fracture at 250 ℃.