双相钢的铁素体晶粒尺寸控制及其对力学性能和氢扩散性能的影响

Ferrite grain size control of dual phase steel and its effect on mechanical properties and hydrogen diffusion properties

通过920℃两相区奥氏体化3 min+形变热处理的热模拟工艺制备了三种不同马氏体晶粒尺寸的铁素体-马氏体双相钢,利用扫描电子显微镜、透射电子显微镜和拉伸试验对三种不同铁素体晶粒度的铁素体-马氏体双相钢的显微组织和力学性进行了表征,利用氢渗透试验对其氢扩散行为进行研究。结果表明:在同一马氏体含量水平(约30%)下,随着双相钢铁素体晶粒尺寸由11.6μm下降至2.3μm和1.1μm,铁素体-马氏体材料的屈服强度和抗拉强度显著增大,其中抗拉强度由865 MPa增大至965 MPa和1 030 MPa,但三者材料的屈强比和延伸率变化不大。随着铁素体晶粒的细化,马氏体带被铁素体隔离,有效增强马氏体可塑性的同时,减缓了氢在试验钢中的扩散,氢扩散系数由3.91×10^(-12)m^(2)/s下降为2.71×10^(-12)m^(2)/s和9.80×10m^(2)/s。

Three different ferrite grain-sized ferrite-martensite dual-phase steels were prepared by largestrain warm deformation at different deformation temperatures in a thermal simulation process,followed by intercritical annealing at 920 ℃ for 3 min in this study. The dimensions were 11.6,2.3 μm, and 1.1 μm, respectively, with the same content of martensite(about 30%.). The microstructure and mechanical properties of three ferrite-martensite dual-phase steels with different ferrite grain sizes were characterized by SEM, TEM and tensile test. The results show that the yield strength and tensile strength of ferrite-martensite materials increase significantly with the decrease of ferrite grain size from 11.6 to 2.3 and 1.1 μm at the same martensite content level(about 30%), the tensile strength increases from 865 MPa to 965 MPa and 1030 MPa, but the yield strength ratio and elongation of the three materials change little. With the refinement of ferrite grains, martensite bands are segregated by ferrite, which effectively enhances the plasticity of martensite and slows down the diffusion of hydrogen in test steel, The hydrogen diffusion coefficient decreased from 3.91×10^(-12)m^(2)/s to 2.71×10^(-12)m^(2)/s and 9.80×10^(-12)m^(2)/s.