固溶处理对2205双相不锈钢组织与疲劳裂纹扩展规律的影响

Effects of solution treatment on microstructure and fatigue crack propagation behavior of 2205 duplex stainless steel

采用光学显微镜、扫描电镜、EDS能谱分析和力学性能测试等方法,研究了固溶处理对2205双相不锈钢显微组织与疲劳裂纹扩展规律的影响。结果表明：与原始热轧态相比,在950-1150℃范围固溶处理的试样的疲劳裂纹门槛值显著提高,稳态裂纹扩展速率均有所减小。在950℃固溶处理时,组织中析出少量的σ相,试样的稳态裂纹扩展速率显著降低;随着固溶温度的升高,组织中α相含量逐渐增加,σ相溶解,试样的稳态裂纹扩展速率的变化呈现为先增大后减小的趋势;当固溶温度达到1150℃时,组织中α相含量最高且两相组织明显粗化,试样的稳态裂纹扩展速率达到最小,呈现出最高的抗疲劳裂纹扩展能力。固溶处理引起σ相的析出与溶解、α相含量的增加及组织粗化是引起2205双相不锈钢试样疲劳裂纹扩展性能非单调变化的原因。

Effects of solution treatment on microstructure and fatigue crack propagation behavior of 2205 duplex stainless steel（DSS）were studied by means of light microscopy,scanning electron microscopy,EDS and mechanical testing,etc.The results show that compared with the commercial hot-rolled plate,the fatigue crack growth threshold of solution-treated samples all increases obviously and the steady fatigue crack propagation rate all decreases with the samples solution treated in the range of 950 to 1150℃.At 950℃,σphase is precipitated along the boundary betweenαphase andγphase and inαphase,which leads to an obvious decrease of the steady fatigue crack propagation rate.With the further increase of solution temperature,the volume fraction ofαphase increases gradually,σphase dissolves,and the steady fatigue crack propagation rate increases at first and then decreases.When the solution temperature reaches 1150℃,the volume fraction ofαphase gets a maximum,duplex crystal particle coarsens,and the steady fatigue crack propagation rate becomes a minimum.Meanwhile,the sample exhibits highest fatigue crack resistance.The phase transformation fromγphase toαphase and the precipitation and dissolution ofσphase both in theαphase and along the duplex boundary together with the crystal particle coarsening might be the reason for the non-monotonic variation of fatigue of DSS2205.