两种不同热处理工艺对铸造IN 939合金微观组织及室温拉伸性能的影响

Effect of two different heat treatment processes on microstructure and room temperature tensile properties of as-cast IN 939 alloy

对铸态IN 939(Inconel 939)合金进行了两种不同工艺的热处理:固溶+时效(SA),双固溶+双时效(DSA),并研究了热处理对其显微组织及室温拉伸性能的影响。结果表明:铸态IN 939合金的显微组织由γ、γ′、MC碳化物、η相及γ/γ′共晶组成,其中γ′相有细小和粗化两种形貌。固溶+时效热处理后合金内的η相和粗大γ′相固溶进基体中重新析出细小γ′相,由于细小γ′相充分弥散而得到较为均匀的组织,MC碳化物转变为M_(23)C_(6)和少许粗化的γ′相;双固溶+双时效热处理使得合金中溶解了更多的析出相,使显微组织更均匀,γ′相充分长大。两种工艺热处理后合金的室温拉伸屈服强度较铸态都有一定提高,固溶+时效热处理试样提升了13.5%,双固溶+双时效试样提升了2.2%,但室温抗拉强度和塑性相比于铸态均有所降低。铸态IN 939合金的断裂机制属于韧性断裂,而SA和DSA试样均属于脆性断裂,DSA试样与SA试样相比,其室温下的塑性和拉伸性能都相对较好。

As-cast IN 939(Inconel 939)alloy was heat treated by two different processes:solution+aging(SA)and double solution+double aging(DSA),and the effect of heat treatment on its microstructure and room temperature tensile properties was studied.The results show that the microstructure of the as-cast IN 939 alloy consists ofγ,γ′,MC carbide,ηandγ/γ′eutectic phases,and theγ′phase has two morphology:fine and coarsened.After solution+aging treatment,theηand coarseγ′phases in the alloy are dissolved into the matrix and reprecipitated in the form of fineγ′phase,the fineγ′phase is fully dispersed so that the alloy has a more uniform structure,and the MC carbide is transformed into M_(23)C_(6)carbide and a little coarsenedγ′phase.Double solution+double aging treatment makes more precipitates dissolved in the alloy,resulting in more uniform microstructure,and theγ′phases grow sufficiently.The yield strength at room temperature of the alloy after heat treatment by the two processes is higher than that of as-cast alloy,and increases by 13.5%after solution+aging treatment and 2.2%after double solution+double aging,respectively,but the tensile strength and plasticity at room temperature are lower than that of as-cast alloy.The fracture mechanism of the as-cast IN 939 alloy belongs to ductile fracture,while that of SA and DSA samples belong to brittle fracture.Compared with SA sample,DSA sample has better plasticity and tensile properties at room temperature.