变形温度对Fe-23Mn-2Al-0.2C TWIP钢变形机制的影响

EFFECT OF DEFORMATION TEMPERATURE ON TENSILE DEFORMATION MECHANISM OF Fe-23Mn-2Al-0.2C TWIP STEEL

利用控温拉伸实验,结合微观组织形貌观察和层错能的计算,分析了在-60—600℃温度范围变形时高锰TWIP钢Fe-23Mn-2Al-0.2C力学性能和显微组织的变化规律及变形温度对其变形机制的影响.结果表明,随着变形温度的升高,TWIP钢的强度和延伸率总体上呈现先降低后增加,然后又降低的趋势.在300℃变形时,强度和延伸率均出现峰值;随着变形温度由-60℃升高到600℃,层错能逐渐增加,其变形机制由孪生为主转变为以滑移为主;低温变形时,组织中存在大量形变孪晶,随变形温度升高,形变孪晶数量逐渐减少.当变形温度达到600℃时,未发现孪晶,主要存在位错,并出现大量的位错胞,试样发生软化;低温变形时产生的高密度形变孪晶诱发的塑性使TWIP钢具有良好的低温力学性能.

Twinning-induced plasticity（TWIP） steel can be classified into three types,Fe-Mn -Al-Si,Fe-Mn-C and Fe-Mn-Al-C steels.Owing to their high strength,superior plasticity and good formability,they have potential applications in automobile manufacturing industry as a new generation of steels.In order to reveal the dependence of deformation mechanism on temperature for Fe-23Mn-2Al-0.2C TWIP steel,microstructural observation,stacking fault energy calculation and tensile deformation experiments were performed at a temperature range from -60℃to 600℃.With increasing the deformation temperature,the strength and elongation to failure of this steel firstly decrease,then increase and finally decrease.And their peak values appear at 300℃during high temperature deformation.As deformation temperature increased from -60℃to 600℃,the stacking fault energy of the steel increases and the deformation mechanism is changed from twining to slipping. Deformation twins with high density appear at lower deformation temperatures,however,they will gradually decrease with increasing temperature.When the sample was deformed at 600℃,only dislocations and dislocation cells appear.High-density deformation twins formed during low-temperature deformation result in the high tensile strength and elongation to failure in this steel.