TiAl基合金热轧板材的各向异性

摘要

利用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和拉伸力学试验等方法对铸锭冶金Ti-45Al-7Nb-0.3W合金热轧板材力学性能的各向异性进行研究.结果表明:Ti-45Al-7Nb-0.3W合金热轧板材具有明显的力学性能各向异性,在室温条件下,沿轧制方向的屈服强度σRD为445 MPa,高于沿横向的屈服强度σTD;在800℃条件下,σRD为522 MPa,低于σTD.织构和显微组织表明:经热轧变形后,板材中存在明显{100}<010>立方织构,即面心四方γ晶胞的c轴平行于横向;在轧制纵截面上,板材显微组织表现为拉长的γ晶粒和α2/γ层片晶团;在横截面上,板材显微组织表现为等轴的γ晶粒和α2/γ层片晶团.Ti-45Al-7Nb-0.3W合金热轧板材力学性能的各向异性是由织构和显微组织的差异所致.%The anisotropy of mechanical properties of ingot metallurgical Ti-45Al-7Nb-0.3W alloy hot-rolling sheet was investigated by optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffractometry and tensile test. The results indicate that the hot-rolling sheet presents significant anisotropy of mechanical properties, at room temperature, the yield strength of rolling direction(RD) is 445 MPa, which is higher than that of the transverse direction(TD); while at 800℃, the yield strength of rolling direction(RD) is 522 MPa, which is lower than that of the transverse direction(TD). The texture and microstructure analysis results indicate that there exists a strong cube texture {100}<010> in the rolling sheet, i.e., the<001>c-axes of the tetragonalγ-TiAl unit cells parallel to the TD. And along the rolling direction the microstructure of TiAl alloy hot-rolling sheet are composed of elongatedγ grains andα2/γ lamellar colonies, while along the transverse direction the microstructure is composed of elongatedγ grains andα2/γ lamellar colonies. The existing texture and difference of microstructure result in the mechanical anisotropy of Ti-45Al-7Nb-0.3W alloy hot-rolling sheet.