Columnar crystal Mg-6.52Zn-0.67Y alloy with (11 2 0)<0001> preferential orientation was prepared by directional solidification technique. The deformation and fracture mechanism were investigated in directionally solidified alloy through stretch test at room temperature and high temperature by using SEM, XRD and EBSD analysis methods. The results show that, directionally solidified Mg-6.52Zn-0.67Y alloy at room temperature has a certain uniform plastic deformation capacity because its yield strength and tensile strength are 124 MPa and 196 MPa, respectively, and its elongation is 13%. With the increase of the tensile temperature, the strength of the alloy decreases, the plasticity increases. At 150 ℃, the tensile strength is 146 MPa and the elongation increases to 27%. At 300 ℃, the tensile strength is down to 73 MPa and the elongation is up to 35%. The deformation mechanism is not only pyramidal, prismatic slip but also{10 1 2} and {10 1 1} twins twin jointly, and the fracture mechanism is a mixture cracking mechanism (ductile fracture and quasi cleavage fracture) at 150 ℃ or 200 ℃. With the tensile temperature reaches to 300 ℃, the deformation mechanism is pyramidal slip and dynamic recrystallization, and the fracture mechanism is ductile fracture.%利用定向凝固技术制备具有(1120)<0001>择优取向的柱状晶 Mg-6.52Zn-0.67Y 合金.对定向凝固Mg-6.52Zn-0.67Y合金进行室温及高温拉伸实验,并利用SEM、XRD和EBSD等分析方法研究合金的拉伸断口、形变过程中组织演变及断裂机制.结果表明:定向凝固Mg-6.52Zn-0.67Y合金的室温σ0.2和σb分别为124和196 MPa,δ为13%,表明定向凝固合金室温下具有一定的均匀塑性变形能力;随着拉伸温度的升高,合金的强度降低,塑性升高,150 ℃拉伸时其σb为146 Ma,δ升至27%;300 ℃拉伸时其σb降至73 MPa,δ高达35%.150 ℃和200 ℃拉伸时其主要形变机制为锥面、棱柱面滑移及{1012}孪生和{1011}孪生等共同作用,合金的断裂机制为韧性断裂和准解理的复合断裂; 300 ℃拉伸时,主要形变机制则为锥面滑移和动态再结晶,合金的断裂机制为韧性断裂.
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