两步热处理制备高延性TiAl基合金机理

Formation mechanism of a high ductility TiAl-based alloy made by two-step heat treatment

研究了两步热处理对锻造Ti 4 7Al 2Cr(摩尔分数 ,% )组织演变和室温拉伸性能的影响。经 12 90℃ ,4h FC12 4 0℃ ,4h ,FC +90 0℃ ,2 4h热处理后 ,锻造TiAl基合金中形成了均匀细小的双态组织 ,其室温伸长率 ,室温抗拉强度和室温屈服强度分别为 3.5 % ,6 77MPa和 5 97MPa。在热处理过程中 ,锻造TiAl基合金发生了复杂的相变 ,其相变过程为 :变形组织→γf+αf→γf+(αf+γs+αs)→γf+Lf+γs+Ls。当第二步热处理温度偏低时 ,αs 转变为脆性α2 相颗粒 。

The effect of two step heat treatment on the microstructure evolution and room tensile properties of forged Ti 47Al 2Cr (mole fraction, %) was investigated. After the heat treatment of 1?290?℃, 4hFC1?240?℃, 4?h, FC+900?℃, 24?h, the uniform fine duplex microstructures are formed in forged TiAl based alloy and its room temperature tensile ductility, tensile strength and yield strength reach 3.5%, 677?MPa and 597?MPa respectively. The formation of uniform fine duplex microstructures results from the complex phase transformation of forged microstructures→ γ f+ α f→ γ f+( α f+ γ s+ α s)→ γ f+ L f+ γ s+ L s. When the temperature of the second step heat treatment is lower, the transformation of α s into brittle α 2 phase particles leads to the decrease of room temperature tensile properties.