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采用XRD,SEM,TEM,硬度测试和拉伸实验研究了冷轧Mn12Ni2Mo Ti(Al)钢经不同工艺退火后的显微组织及力学性能.结果表明,马氏体Mn12Ni2Mo Ti(Al)钢经65%冷轧及710~745℃退火处理后转变成主要由奥氏体晶粒和铁素体晶粒组成的亚微米级超细晶粒双相组织,并且弥散分布着第二相析出物颗粒;在退火中形成的富Ti,Mo及Si的第二相颗粒阻碍了超细再结晶晶粒的粗化,从而提高了钢的屈服强度和热稳定性;经710℃,24 h长时间退火后,超细晶粒双相钢的平均晶粒尺寸仍然小于500 nm;超细晶粒双相钢延伸率随室温奥氏体体积分数增加而增加,室温奥氏体体积分数随退火温度升高或退火时间延长先增加后降低,且在745℃,0.5 h退火时达到最大值.超细晶粒钢的屈服强度和总延伸率可达到900 MPa和23%以上,比同种材料淬火马氏体钢提高了约一倍.
The microstructure and mechanical properties of cold-rolled Mn12Ni2Mo Ti (Al) steel after different annealing processes were studied by XRD, SEM, TEM, hardness test and tensile test. The results show that the martensitic Mn12Ni2Mo Ti (Al) % Cold-rolled and annealed at 710-745 ° C to form a sub-micron ultrafine grain dual phase structure mainly composed of austenite grains and ferrite grains, and particles of second phase precipitates are dispersedly distributed; The second phase particles rich in Ti, Mo and Si formed during annealing prevent the coarsening of the ultrafine recrystallized grains, thereby improving the yield strength and thermal stability of the steel. After annealed at 710 ° C. and 24 h for a long time , The average grain size of ultrafine-grained dual-phase steel is still less than 500 nm; the elongation of ultrafine-grained dual-phase steel increases with the increase of the volume fraction of austenite at room temperature, the room temperature austenite volume fraction increases with annealing temperature or The annealing time increases firstly and then decreases, and reaches the maximum value at 745 ℃ and 0.5 h annealing.The yield strength and total elongation of ultra-fine grain steel can reach 900 MPa and 23%, which are higher than that of quenched martensite Steel is about doubled.