Nb微合金化Fe-25Mn-3Si-3Al TWIP钢的组织与力学性能

Microstructure and mechanical properties of Nb micro-alloyed Fe-25Mn-3Si-3Al TWIP steel

向Fe-25Mn-3Si-3Al TWIP钢中添加0.35%的Nb,提高钢中C元素含量至0.1%,并配合适当热处理工艺以提高TWIP钢的屈服强度。结果表明:改进后的Fe-25Mn-3Si-3Al-0.3Nb-0.1C钢的屈服强度由原来的320 MPa提高至445 MPa,均匀伸长率则由65%降低至55%。Nb元素的添加会强烈阻碍TWIP钢的再结晶晶粒的长大,显著细化TWIP钢的奥氏体晶粒,并且添加的Nb、C元素经退火处理后主要以纳米级Nb C沉淀相的形式弥散分布于奥氏体基体上,这些细小的沉淀相将通过Orowan机制进一步提高TWIP钢的强度。此外,Nb、C元素的添加并未显著改变室温下Fe-25Mn-3Si-3Al TWIP钢的塑性变形机制,应变诱发孪晶仍然是Fe-25Mn-3Si-3Al-0.3Nb-0.1C钢的主要变形机制,奥氏体基体仍然维持着较低的层错能。通过细晶强化和沉淀强化的双重作用显著提高Fe-25Mn-3Si-3Al TWIP钢的强度,同时奥氏体基体的TWIP效应保证了改进后的TWIP钢仍具有良好的塑性。

A Fe-25Mn-3Si-3Al TWIP steel was modified by the additions of 0. 35% Nb and 0. 1% C,and then an appropriate heat treatment process was used to improve its yield strength. The results show that the yield strength of Fe-25Mn-3Si-3Al TWIP steel increases from 320 MPa to 445 MPa,but the uniform elongation of the modified steel decreases from 65% to 55% after the modification. The addition of Nb can strongly hinder the growth of austenitic grains,and refines the recrystallized grain size of the high-Mn TWIP steel,moreover,Nb atoms combine with C atoms to form the nanoscale Nb C precipitated phase,and these nanoscale precipitated particles are dispersively distributed in austenitic matrix,which can prevent the dislocation movement and improve the yield strength of the high-Mn TWIP steel by the Orowan mechanism. Furthermore,the additions of Nb and C elements can not obviously change the deformation mechanism of Fe-25Mn-3Si-3Al steel at room temperature,and the strain-induced twinning is still a main deformation mechanism for the modified Fe-25Mn-3Si-3Al-0. 3Nb-0. 1C steel. The stacking fault energy of Fe-25Mn-3Si-3Al-0. 3Nb-0. 1C steel still remains a low level.And finally, the yield strength and tensile strength of Fe-25Mn-3Si-3Al steel are significantly improved by grain refinement and precipitation strengthening,and the twinning induced plasticity effect of the austenitic matrix provides a satisfactory ductility for the modified steel.