铜合金化对Fe-18Mn-0.6C TWIP钢低温韧性的影响

Effect of Cu alloying on cryogenic-temperature toughness of Fe-18Mn-0.6C TWIP steel

TWIP(twinning induced plasticity)具有高强塑性、高抗冲击韧性和高低温性能等优点。目前市场应用较多的是以Fe-18Mn-0.6C为基的TWIP钢。高性能TWIP钢的工业化生产和推广可实现中国钢铁产业品种规格齐全化和推广高附加值钢铁材料。通过一定的合金化设计进一步提升其低温/超低温强韧性,可成为能源储存及运输用钢的有效替代钢材。在Fe-18Mn-0.6C TWIP钢中加入了不同含量的Cu合金元素,通过拉伸试验和室温到低温/超低温冲击试验,结合OM、XRD、SEM和EBSD等表征,研究了Cu合金对热轧TWIP钢微观组织和力学性能的影响,特别针对Cu合金化对低温/超低温冲击韧性的提升作用。结果表明,试验采用的热轧TWIP钢为单一奥氏体组织,Cu合金对TWIP钢有明显的晶粒细化效果,同时又增加了晶界取向差的均匀性。未添加Cu的TWIP钢因其平均晶粒尺寸更大,表现出更高的应变强化效果,强塑性更高。Cu合金对TWIP钢冲击韧性的提升较为明显。随着Cu合金元素含量的增加,TWIP钢的冲击功逐渐增大;室温下含2.9%Cu(质量分数)的TWIP钢冲击功达到375 J。随冲击温度的降低,不含Cu的TWIP钢冲击韧性下降明显;而含Cu的TWIP钢在-180℃的超低温下冲击功仍然保持在200 J以上。这与Cu的合金化增加SFE、减少低温下SFE的下降、抑制ε-马氏体相变和提高低温下固溶强化效果有关。TWIP钢即使在低温下仍然可以保持韧性断裂特征,仅有不含Cu的TWIP钢在-180℃的超低温冲击后局部出现了少量脆性断裂形貌。

TWIP(twinning induced plasticity)steel t has the advantages of high strength and ductility,high impact toughness and high low-temperature performance.At present,the Fe-18Mn-0.6C based TWIP is widely used in the market.The industrial production and promotion of high-performance TWIP steel can achieve complete variety specifications of China′s steel industry and promote high value-added steel materials.Through a certain alloying design to further improve its low-temperature strength and toughness,it can become an effective alternative steel for energy storage and transportation.Cu with different contents were added to Fe-18Mn-0.6C TWIP steel.Through tensile test at room temperature and impact test from room temperature to low/ultra-low temperature,with OM,XRD,SEM and EBSD et al.for characterization to found the effect of Cu alloying on the microstructure and mechanical properties of hot-rolled TWIP steel,especially the improvement effect of cryogenic toughness at low tem‐perature/ultra-low temperature by Cu alloying.The results show that the hot-rolled TWIP steels had single austenitic microstructure,and the Cu alloying had significant grain refining effect on the TWIP steel,and also increased the uniformity of grain boundary orientation difference.At room temperature,the TWIP steel without Cu shows higher strength and better plasticity because of its larger average grain size,showing higher strain strengthening effect and higher strength and plasticity balance.The effect of Cu alloying on the impact toughness of TWIP steel is distinct.The impact energy of TWIP steel increased with the increasing Cu content.The impact energy of TWIP steel with 2.9%Cu alloying at room temperature reached 375 J.The impact toughness of TWIP steel without Cu alloying decreased significantly with the decreasing temperature.The impact energy of TWIP steel with Cu alloying remained above 200 J at−180℃.This is related to Cu alloying increasing SFE,reducing SFE decline at low tem‐perature,inhibitingε-martensitic transformation and improving solution strengthening effect at low temperature.TWIP steel can still maintain ductile fracture characteristics with the decreasing temperature to−180℃.Only TWIP steel without Cu alloying had a small amount of local brittle fracture morphology impacted at−180℃.