Ho对时效态Mg-5Y-3Sm-0.5Zr合金组织及力学性能的影响

Effect of Ho on microstructure and mechanical properties of aged Mg-5Y-3Sm-0.5Zr alloy

采用X射线衍射仪、光学显微镜、扫描电镜、能谱仪、电子拉伸实验机等研究了时效态Mg-5Y-3Sm-xHo-0.5Zr(x=0、2、4、6,mass%)合金的显微组织和力学性能。结果表明:时效态Mg-5Y-3Sm-0.5Zr合金的组织由α-Mg基体和第二相Mg_(24)Y_(5)、Mg_(41)Sm_(5)组成,添加稀土元素Ho后有新相Mg_(24)Ho_(5)生成;适量Ho的添加能够细化时效态Mg-5Y-3Sm-0.5Zr合金的晶粒,提高其室温及高温力学性能;在室温(20℃)~250℃温度范围内,合金的抗拉强度均随Ho含量的增加呈现先增大后减小的趋势,除200℃略有不同外,合金的抗拉强度均在Ho含量为4%时达到峰值。含4%Ho的合金在不超过150℃时,强度非常稳定,对温度变化不敏感;合金拉伸断裂方式主要表现为脆性断裂,当拉伸温度升高时,呈现向微孔聚集断裂转变的趋势。

Microstructure and mechanical properties of aged Mg-5 Y-3 Sm-xHo-0.5 Zr(x=0, 2, 4, 6, mass%) alloys were studied by means of X-ray diffraction, optical microscope, scanning electron microscopy, energy dispersive spectrometer and electronic tensile testing machine. The results show that the microstructure of the aged Mg-5 Y-3 Sm-0.5 Zr alloy is composed of α-Mg matrix and second phase Mg_(24)Y_(5) and Mg_(41)Sm_(5). A new phase Mg_(24)Ho_(5) is formed after adding rare earth element Ho. The addition of appropriate amount of Ho can refine the grain size of the Mg-5 Y-3 Sm-0.5 Zr alloy, and improve its mechanical properties at room temperature and high temperature. The tensile strength of the alloy increases first and then decreases with the increase of Ho content in the temperature range of 20-250 ℃, except for the slight difference at 200 ℃, the tensile strength of the alloy reaches the peak value when the Ho content is 4%. The strength of the alloy with 4% Ho content is very stable and not sensitive to temperature change when the temperature is not higher than 150 ℃. The tensile fracture mode of the alloy is mainly brittle fracture, and it tends to change to micro-pore accumulation fracture when the tensile temperature increases.