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研究了不同热处理条件下σ相的回溶规律及其对合金持久性能的影响.研究发现,在800~900℃范围内经过最长1×104h时效后,合金中产生的σ相率先在枝晶干的M23C6碳化物附近形成,之后扩展到枝晶间;随着时效温度的升高,σ相形成速度加快,σ相形核的孕育时间缩短.激活能计算结果对比表明,σ相形成初期与Co,Cr的扩散相关,稳态阶段与Mo的扩散相关;长期时效后合金在1000~1170℃固溶时,σ相都可以回溶到基体,且固溶温度越高,σ相回溶越快.σ相的回溶动力学研究表明,σ相的回溶速度受Co的扩散过程控制.对比持久实验结果表明,合金中的σ相并不能使合金变脆;经过恢复热处理,长期时效过程中析出的σ相回溶,持久寿命提高.
The effects of heat treatment on the dissolution behavior of sigma phase and its effect on the ductility of the alloy were studied.The results show that the σ phase in the alloy is firstly dendritic after the aging of 1 × 104h at 800-900 ℃, The formation of dry M23C6 carbides, and then extended to the interdendritic; With the aging temperature increases, the formation speed of σ phase, σ phase nucleation incubation time is shortened.Comparison of activation energy calculation results show that the σ phase formation and Co , And the diffusion of Cr. The steady state phase is related to the diffusion of Mo. The σ phase can be dissolved back to the matrix when the alloy is soluted at 1000-1170 ℃ for long-term aging. The higher the solution temperature, the faster the σ phase is dissolved The study on the solution phase of σ phase shows that the dissolution rate of σ phase is controlled by the diffusion process of Co.Compared with the long-term experimental results, the σ phase in the alloy does not make the alloy brittle. After the recovery heat treatment, The precipitated σ phase is dissolved and the longevity is improved.