两相区退火时间对冷轧中锰钢组织和力学性能的影响

Effect of annealing time on microstructure and mechanical properties of a cold rolled medium manganese steel

研究了650℃下退火时间对冷轧Fe-0.14C-5Mn钢的组织结构和力学性能的影响规律,利用SEM进行了组织结构表征,采用XRD法测量了残留奥氏体量,通过拉伸试验机测试了钢的单轴拉伸性能。结果表明,退火过程中发生奥氏体逆转变,退火1min以后即形成20%以上的亚稳奥氏体;随退火时间的延长,抗拉强度(Rm)逐渐升高,屈服强度逐渐降低;断后伸长率(A)和强塑积(Rm×A)先升高而后降低,在650℃退火10 min时塑性(46%)和强塑积(46 GPa%)获得最大值。分析认为高含量亚稳奥氏体相的TRIP效应以及超细的晶粒尺寸是获得超高强度、超高塑性及高的强塑积的主要原因。

Effects of annealing time on microstructure and mechanical properties of cold rolled Fe-0.14C-5Mn steel annealed at 650 ℃ were investigated.Microstructure evolution of the steel during annealing process was characterized by means of scanning electron microscopy.The amount of retained austenite in the steel was determined by X-ray diffraction analysis.Mechanical properties of the annealed steel were studied by tensile tests.It is found that the austenite reverted transformation takes place,which results in more than 20% austenite phase in the ultrafine grained matrix after annealing at 650 ℃ for 1 min.Tensile strength（Rm） of the steel increases and its yield strength（Rp0.2）,decreases with increasing the annealing time.Both elongation to failure（A） and the product of tensile strength to elongation to failure（Rm×A） first increase and then decrease.The maximum values of A（46%） and Rm×A（46 GPa%） are obtained for the steel annealed at 650 ℃ for 10 min.The high mechanical properties with strength Rm of 1000 MPa,elongation A of 46% and product of Rm×A of 46 GPa% are attributed to the enhanced TRIP effects by the large fraction of metastable austenite and the ultrafine grain size.