1500 MPa级含Al低密度马氏体超高强钢的相变行为和力学性能

Phase transformation behavior and mechanical properties of 1500MPa low density martensitic ultrahigh strength steel containing Al

采用全自动相变仪、扫描电子显微镜、电子万能拉伸试验机、宏观硬度计等设备和Thermo-Calc热力学计算软件研究了3种1500 MPa级不同Al元素含量对马氏体超高强钢的相变行为、显微组织和力学性能的影响规律。结果表明,相对于不含Al实验钢,Al质量分数为3%实验钢的Ac1温度提高了24℃,Al质量分数为1.5%实验钢的Ac3温度提高了99.8℃,并且与不含Al实验钢相比,含3%Al的实验钢密度降低4.15%。随着Al含量的增加,实验钢热轧后直接水冷至室温的组织由单一的板条马氏体转变为马氏体+沿轧向拉长的铁素体两相层状组织。由于固溶强化以及混合法则的影响,马氏体超高强钢的抗拉强度与硬度都随Al含量的增加呈现出先增加后减少的趋势,1.5Al钢轧向抗拉强度达到1723 MPa,硬度达到530HV,而3Al钢轧向-40℃低温冲击韧性最大可达到363 J。

The effect of three kinds of Al content on the phase transformation behavior,microstructure and mechanical properties of martensitic ultra-high strength steel was studied by automatic phase change instrument,scanning electron microscope,electronic universal testing machine,macro-hardness tester and Thermo-Calc thermodynamic calculation software.The results show that compared with the experimental steel without Al,the Ac1 temperature of 3 wt.%Al is increased by 24℃,and the Ac3 temperature of 1.5 wt.%Al is increased by 99.8℃,and the density of 3 wt.%Al is decreased by 4.15%compared with the experimental steel without Al.With the increase of Al content,the microstructure of the experimental steel directly cooled to room temperature after hot rolling changes from single lath martensite to martensite+ferrite two-phase layered microstructure along the rolling direction.Due to the influence of solution strengthening and mixing rule,the tensile strength and hardness of martensitic ultra-high strength steel firstly increase and then decrease with the increase of Al content.The tensile strength and hardness of 1.5Al rolled steel reach 1723MPa and 530HV,while the maximum impact toughness of 3Al rolled steel at-40℃can reach 363J.