冷变形MP35N合金的时效强化机理

Strengthening mechanisms of cold worked MP35N alloy during aging treatment

摘要:

为研究MP35N合金时效强化规律及机制，对MP35N合金进行84.18%的冷轧变形后，进行时效处理研究.在万能拉伸机上进行力学性能测试，用OM、SEM、TEM和EDS进行组织分析和微观成分测试.实验结果表明：在500 ℃时效4 h时，显微硬度达到最大值704.26 HV，抗拉强度为2641.16 MPa，与冷轧态相比，分别提高了30.44%和37.41%；该合金经时效后冷轧撕裂孔洞愈合，在400 ℃时效后出现了由3~4个厚度为3 nm左右的细小孪晶组成的“孪晶簇”；温度升高到500 ℃，孪晶尺寸变大、交错，“孪晶簇”消失.未发现Mo原子在孪晶处处偏聚，时效过程中形成的纳米级片状孪晶起到主要的强化作用.

Abstract:

The strengthening mechanism during aging treatment after 84.18% cold rolling of MP35N alloy was performed in this study. Mechanical properties were tested on universal tensile testing machine and the microstructures were analyzed by OM, SEM, TEM and EDS. The results show that the maximum micro-hardness, 704.26 HV, was obtained when MP35N alloy was aged at 500 ℃ for 4 h, at which state the tensile strength was 2641.16 MPa. The two values increased by 30.44% and 37.41% over cold rolling state respectively. Tear holes which formed during cold forming healed after aging and the TEM result revealed that the thin "twin cluster" consisting of 3 to 4 fine twins which thickness about 3 nm appeared after aged at 400 ℃. When the temperature increased to 500 ℃, twin size became larger, staggered and then "twin cluster" disappeared. The EDS results shows there is no obvious concentration of Mo atom occurred in the twins. Nano flake twins formed during aging treatment play a major role in strengthening.