中文摘要：

针状铁素体组织强度高、韧性好，基于氧化物夹杂形核，有很强的自身细化晶粒的能力，获得大量超细针状铁素体组织是超级钢研究的主要发展方向。建立了Fe—C-X系合金针状铁素体在奥氏体贫碳区先共析转变的热力学模型，并对Q235钢进行了数值模拟。结果表明，针状铁素体在实际相变开始温度（约923K）的相变驱动力（绝对值）为450-740J／mol，而且随着贫碳区碳含量的减少而增加。该模型可获得比以往扩散模型更大的相变驱动力，从热力学角度来讲，针状铁素体在奥氏体贫碳区很可能具有先共析转变的相变过程。

英文摘要：

Acicular ferrite microstructure has high strength and good toughness, nucleates around oxide inclusions and possesses strong grain-refining ability by itself. The main development direction of the ultra steel research is to get a great many of acicular ferrites. A thermodynamic model of pre-eutectoid transition of acicular ferrite in carbon-depleted regions of austenite was established, and used in the numerical simulation of Q235 steel. The results show that the absolute value range of driving force of acicular ferrite formation at 923 K is from 450 to 740 J/mol, and the driving force in carbon depleted region increases ,with the reduction of carbon concentration. The driving force calculated by this model can be larger than that by any other diffused model. So in aspect of thermodynamics, acicular ferrite is most likely to transform in pre-eutectoid way in carbon-depleted regions of austenite.