Fe-Cr-Ni-Al-Mo-Si铁素体钢的组织及力学性能

Microstructure and mechanical properties of Fe-Cr-Ni-Al-Mo-Si ferritic steel

采用光学显微镜、扫描电镜、能谱分析和X-射线衍射仪研究了Fe-Cr-Ni-Al-Mo-Si钢铸态及热处理后的显微组织和力学性能。结果表明,试验钢铸态显微组织主要由铁素体基体、沿晶界分布的奥氏体及大小为430~480 nm均匀分布的立方状Ni Al相和分布在Ni Al相上的细小球状Ni Al相组成;经1200℃×0.5h空冷固溶处理后在空冷过程中析出大小为50~100nm弥散分布的球状Ni Al相;固溶处理后再在750、1000℃时效处理1 h,Ni Al相较固溶态粗化,1000℃时效后在铁素体上有奥氏体相析出;拉伸结果表明:在固溶和750℃时效条件下,试验钢无室温韧性,在1000℃时效后由于奥氏体相的析出其室温韧性和规定塑性延伸强度明显提高,抗拉强度值达到了1096 MPa,规定塑性延伸强度为860 MPa;在700℃/150 MPa条件下的蠕变试验表明,固溶态试验钢的稳态蠕变速率最低,达到了6.83×10^-12s^-1,然而,奥氏体相的析出并不能有效提高其抗蠕变性能。

The microstructure and mechanical properties of a Ni Al-type phase strengthened ferritic steel both in as-cast and heat-treated conditions were investigated by means of optical microscope,scanning election microscopy,and X-ray diffractometer.The results show that the cast microstructure of the tested steel consists of ferrite,austenite distributed along grain boundary and cubic Ni Al-type precipitates with a size of around 430-480 nm homogeneously distributed in the ferritic matrix.The Ni Al-type precipitates can be refined to 50-100 nm after solution treatment at 1200℃for 0.5 h followed by air cooling.The aging treatment following the solution treatment causes these precipitates coarse,and after aging treatment at 1000℃,the austenite phase is formed along the ferrite grain boundary.Tensile test results show that the steel has no room temperature ductility in the condition of both solution-treatment and aging treatment at 750℃,but they can be significantly improved after aging treatment at 1000℃because of the formation of austenite phase,the tensile strength reaches 1096 MPa and the yield strength is 860 MPa.The creep test result under the condition of 700℃/150 MPa shows that the steady-state creep rate of solid solution tested steel is the lowest,reaching 6.83×10^-12s^-1.However,the formation of austenite phase is not beneficial for the creep resistance.