将实验V-Nb-Mo微合金钢在1200℃固溶处理,在500℃回火不同时间,用场离子显微镜（FIM）研究实验钢中碳化物的析出过程。结果表明：回火0.5 h的样品中,碳化物处于形核长大时期,与基体的{110}呈共格关系;随着回火时间的延长,碳化物形成独立的晶体结构,与基体{110}之间呈半共格关系;回火100 h后,碳化物粗化长大,与基体呈非共格关系;形状系数随着回火时间的延长先变大再变小,析出相尺寸从1.6 nm逐渐增大至15 nm。500℃回火30 h的实验钢力学性能最佳,表明碳化物的析出强化效果最明显,相应的碳化物尺寸约为4 nm。
The precipitation reaction of nano-carbides in a quenched and tempered V-Nb-Mo microalloyed steel was studied by field ion microscopy（FIM）.The experimental steel was quenched after the solution treatment at 1200 ℃ for 0.5 h,and then tempered at 500 ℃ for different time.The FIM results show that the size of precipitates varies from 1.5 nm to 15 nm as the tempering time is prolonged from 0.5 h to 100 h.It is very clear that the nano-carbide nucleates at {110} planes of ferrite matrix coherently in the initial stage of tempering.The precipitates gradually grow bigger as tempering continues and finally become incoherent with the matrix.Further analysis shows that the maximum precipitation strengthening effect is obtained when the size of precipitates approaches to 4 nm in the steel tempered at 500 ℃ for 30 h.
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