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对低碳钢在Ae_3以上进行了单道次快速大形变量变形,测定了材料在高温变形前后的室温拉伸曲线并观察其断口形貌。对结果的分析表明,低碳钢在Ae_3以上的温度发生形变诱导铁素体相变,是形成超细晶粒(3μm左右)的主要原因。应变速率大于0.1 s~(-1)时,可诱导形成铁素体晶粒,且随着应变速率的提高铁素体分数增加而晶粒尺寸减小;当应变速率大于10 s~(-1)时铁素体分数达到饱和,晶粒尺寸的变化不大。与先共析铁素体相比,形变诱导铁素体的强度和硬度大大提高,低碳钢Q235的屈服强度由250 MPa左右提高到510 MPa,抗拉强度则达到615 MPa,而形变诱导铁素体的塑性有所降低,但仍保持较高的水平。
The single-pass rapid deformation of mild steel above Ae_3 was carried out. The tensile curves at room temperature before and after high temperature deformation were measured and the fracture morphology was observed. The analysis of the results shows that the deformation induced ferrite transformation occurs at a temperature above Ae_3, which is the main reason for the formation of ultra-fine grains (about 3μm). When the strain rate is more than 0.1 s ~ (-1), the ferrite grains can be induced and the grain size decreases with the increase of the strain rate. When the strain rate is more than 10 s ~ (-1) ) When the ferrite fraction reaches saturation, little change in the grain size. Compared with the pro-eutectoid ferrite, the strength and hardness of the deformation-induced ferrite are greatly improved. The yield strength of low carbon steel Q235 is increased from about 250 MPa to 510 MPa and the tensile strength is up to 615 MPa. The deformation induced iron The body’s plasticity decreased, but still maintain a high level.