时效温度对铸态低密度钢Mn30Al9Si组织及性能的影响

Effect of aging temperature on microstructure and properties of as-cast low density steel Mn30Al9Si

通过X射线衍射(XRD)、透射电镜(TEM)、电子背散射衍射(EBSD)以及拉伸实验等研究了时效温度对铸态奥氏体基低密度钢(Mn30Al9Si)组织及力学性能的影响,并研究了其强韧化机制。结果表明:铸态Mn30Al9Si钢经固溶时效后的组织由奥氏体基体及条状铁素体组成,并包含κ-碳化物、β-Mn等第二相;450℃时效后试验钢获得了优异的强塑性结合,其抗拉强度为732 MPa,伸长率为52.91%;500℃时效后,由于β-Mn相在铁素体/奥氏体边界析出,其伸长率由52.91%下降到6.31%;550℃时效过程中,由于β-Mn相持续析出并长大以及κ-碳化物的不断长大并分布在奥氏体晶界,使伸长率下降至0.67%。Mn30Al9Si钢的变形区TEM组织具有典型的平面滑移特征,奥氏体基体中存在大量畴界及交叉微带,赋予了试验钢优秀的强塑性,其强韧化机制以微带诱发塑性为主。

Effect of aging temperature on microstructure and mechanical properties of as cast low density steel(Mn30 Al9 Si)was studied by means of X-ray diffraction(XRD),transmission electron microscopy(TEM),electron backscatter diffraction(EBSD)technique and tensile test,and the strengthening and toughening mechanism was also studied.The results show that the microstructure of as cast Mn30 Al9 Si steel after solution and aging treatment is composed of austenite matrix and strip ferrite,and contains second phases such asκ-carbide andβ-Mn.After aging at 450℃,the experimental steel has excellent strength and plasticity,which the tensile strength is 732 MPa and the elongation is 52.91%.After aging at 500℃,the elongation decreases from 52.91%to 6.31%due to the precipitation ofβ-Mn phase at ferrite/austenite boundary.During aging at 550℃,the elongation decreases to 0.67%due to the continuous precipitation and growth ofβ-Mn phase and the continuous growth ofκ-carbide and distribution at austenite grain boundary.The TEM microstructure in the deformation zone of the Mn30 Al9 Si steel has a typical plane slip feature,there are a lot of domain boundaries and crossed microband in the austenite matrix,which endows the experimental steel with excellent strength and ductility,and the strengthening and toughening mechanism is mainly microband-induced plasticity(MBIP).