摘要
2000 MPa级超高强钢是极端服役环境用的关键结构材料,面临严重的强塑性倒置、合金昂贵、生产制备工艺复杂等难题。为此,设计了低成本C-Mn成分体系,研究不同调质温度对实验钢微观组织和力学性能的影响。结果表明,随着调质温度的增加,实验钢的原始奥氏体由带状向等轴状转变,在780℃调质时,带状原始奥氏体晶粒宽约4μm、长约14μm,等轴状原始奥氏体晶粒宽约3μm、长约5μm。实验钢的位错密度随调质温度的增加,从6.87×10^(15)m^(-2)降至5.27×10^(15)m^(-2),再降低至4.46×10^(15)m^(-2)。实验钢室温下残余奥氏体(retained austenite,RA)的体积分数由12.6%降至10.2%再降至9.2%,变形前后RA的体积分数变化值由7.1%降至6.8%再升至7.1%。样品Q780的综合力学性能最好,其屈服和抗拉强度最大,分别为1665和2107 MPa,均匀伸长率也相对较高,为8.9%。5 mm厚V口Q780试样的室温裂纹萌生能(9.8 J)和裂纹扩展能(3.9 J)也相对较高,使其室温冲击功最高为13.7 J。其优异性能归因于最大的位错密度(6.87×10^(15)m^(-2))、最大的RA体积分数(12.6%)和最小的马氏体平均晶粒尺寸(0.77μm)。
2000 MPa ultrahigh-strength steel is a key structural material for extreme service environments and faces serious problems such as strength-ductility inversion,expensive alloys,and complex production and preparation processes.To this end,a low-cost C-Mn composition system was designed,and the effects of different quenching and tempering temperatures on the microstructure and mechanical properties of the experimental steel were studied.The results show that with increasing quenching and tempering temperatures,the original austenite of the experimental steel changes from banded to equiaxed.When quenched and tempered at 780℃,the width and length of the banded original austenite grains are approximately 4 and 14μm,respectively,and those of the equiaxed original austenite grains are approximately 3 and 5μm,respectively.The dislocation density of the experimental steel also decreases from 6.87×10^(15) m^(-2) to 5.27×10^(15)m^(-2)and then to 4.46×10^(15)m^(-2)with increasing quenching and tempering temperatures.The volume fraction of retained austenite(RA)of the experimental steel at room temperature decreases from 12.6%to 10.2%and then to 9.2%.The variation in the volume fraction of RA before and after deformation decreases from 7.1%to 6.8%and then increases to 7.1%.Sample Q780 has the best comprehensive mechanical properties,with the highest yield and tensile strengths of 1665 and 2107 MPa,respectively,and also a relatively high uniform elongation of 8.9%.The room temperature crack initiation energy(9.8 J)and crack propagation energy(3.9 J)of 5 mm thick Q780 with a V-notch are also relatively high,making its room temperature impact energy as high as 13.7 J.The reasons for its excellent performance are that it has the largest dislocation density(6.87×10^(15)m^(-2)),the largest RA volume fraction(12.6%)and the smallest average martensite grain size(0.77μm).
作者
蒋家乐
李云杰
李小琳
袁国
JIANG Jiale;LI Yunjie;LI Xiaolin;YUAN Guo(State Key Laboratory of Rolling and Automation Northeastern University,Shenyang 110819,China;State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China)
出处
《铸造技术》
2025年第2期153-159,共7页
Foundry Technology
基金
国家自然科学基金(52104371)
西北工业大学凝固技术国家重点实验室开放课题(SKLSP202311)。
关键词
超高强钢
原始奥氏体
调质温度
残余奥氏体
力学性能
ultrahigh-strength steel
original austenite
quenching temperature
retained austenite
mechanical properties
