Q235碳素钢应变强化相变的基本特点及影响因素

在热模拟单向压缩实验中，通过形变参数的变化考察了Q235碳素钢应变强化相变的基本规律及铁素体晶粒细化效果，结果表明，铁素体的超细化在热力学上是由于应变强化相变最大限度地提高了相变过冷度，在动力学上是由于形核集中在局部的高应变区，同时在转变过程中形变不断产生新的形核地点并抑制铁素体生长的结果，实现铁素体的超细化需要一最小变量及一定的应变速率，以使转变完毕并加抑制铁素伯的生长及形变成长条状，应变明显削弱了奥氏体晶粒尺寸的差异带来的铁素体尺寸的差异，应变造成的铁素体动态再结晶进一步细化了晶粒，这种特征是动态转变所特有的，此外，还比较了应变强化相变与无应变及传统近轧控冷铁素体形成时的差异。

HARACTERISTICS OF STRAIN ENHANCED TRANSFORMATION AND ITS INFLUENCING FACTORS IN Q235 PLAIN CARBON STEEL

The characteristics of strain enhanced transformation and ferrite grain refinement are investigated under different processing parameters by thermal simulating tests of Q235 plain carbon steel. Results indicate that the ferrite refinement during strain enhanced transformation is due to the strongly increased undercooling of austenite by deformation in the viewpoint of thermodynamics. Repeated ferrite nucleation in localized high strain regions and the prevention of ferrite growth are the dynamic features of strain enhanced transformation. In order to realize ferrite grain refinement a certain amount of strain and a strain rate are needed to provide sufficient nucleation sites and restrain the growth of ferrite grains or their deformation to elongated form. Strain dramatically decreases the influence of initial austenite grain size on the following transformed ferrite grain size. Ferrite dynamic recrystallization can further refine ferrite grain size which is unique in dynamic transformation. The differences between strain enhanced transformation and normal ferrite transformation as well as traditional TMCP are discussed.