挤压变形对Mg-2.5Nd-0.5Zn-0.5Zr合金微观组织和力学性能的影响

Effect of extrusion on microstructure and mechanical properties of Mg-2.5Nd-0.5Zn-0.5Zr alloy

采用扫描电镜、透射电镜、X射线衍射和拉伸试验等技术,研究了不同挤压比制备出的Mg-2.5Nd-0.5Zn-0.5Zr合金的微观组织和力学性能。结果表明,初始材料为近似等轴晶粒,平均晶粒尺寸约为23.8μm,沿晶界析出大量离异的共晶Mg;Nd相,在晶界处共晶相呈连续网状分布。挤压之后合金组织明显细化,E1(挤压比为7.65)和E2(挤压比为12.56)合金平均晶粒尺寸分别为8.1和6.3μm,力学性能显著提高,E1合金沿挤压方向的抗拉强度、屈服强度和伸长率分别为231 MPa、152 MPa和18.9%;E2合金沿挤压方向的抗拉强度、屈服强度和伸长率分别为257 MPa、213 MPa和22.4%。E2合金板材的各向异性指数与E1合金相比明显降低,结果表明增大挤压比可以有效缓解Mg-2.5Nd-0.5Zn-0.5Zr合金板材的各向异性。

The microstructure and mechanical properties of Mg-2.5 Nd-0.5 Zn-0.5 Zr alloy prepared with different extrusion ratios were studied by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile test. The results show that the initial material is approximately equiaxed grain with average grain size of 23.8 μm. A large number of divorced eutectic Mg;Nd phases are precipitated along the grain boundary, and the eutectic phases present a continuous network distribution at the grain boundary. After extrusion, the microstructure is obviously refined, and the average grain sizes of E1(extrusion ratio of 7.65) and E2(extrusion ratio of 12.56) alloy are 8.1 and 6.3 μm, respectively.The mechanical properties are improved remarkably, and the tensile strength, yield strength and elongation of E1 alloy are 231 MPa, 152 MPa and 18.9%, respectively. The tensile strength, yield strength and elongation of E2 alloy are 257 MPa, 213 MPa and 22.4%, respectively. The anisotropy index of E2 alloy sheet is significantly lower than that of E1 alloy. The results show that the anisotropy of Mg-2.5 Nd-0.5 Zn-0.5 Zr alloy sheet can be effectively alleviated by increasing extrusion ratio.