Effect of increased N content on microstructure and tensile properties of low-C V-microalloyed steels

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• 作者：Shuming Zhang ; Ke Liu ; He Chen ; Xinping Xiao ; Qingfeng Wang ; ^{wqf67@ysu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Fucheng Zhang
• 关键词：Low-carbon V-microalloyed steels ; Increased nitrogen ; Microstructure ; Tensile properties ; Strain-hardening
• 刊名：Materials Science & Engineering A
• 出版年：2016
• 出版时间：10 January 2016
• 年：2016
• 卷：651
• 期：Complete
• 页码：951-960
• 全文大小：4314 K

文摘

The processing of four low-carbon vanadium-microalloyed steels with varying nitrogen (N) content of 30–165 ppm, including preheating at 1200 °C, rapid cooling to 550 °C for isothermal transformation, and air cooling, was simulated using a Gleeble 3500 system. The microstructure of each sample was characterized and the tensile properties measured; a microstructure consisting of granular bainitic ferrite (GBF), acicular ferrite (AF), and martensite/austenite (M/A) constituent formed in all of the samples. Moreover, the increasing N content led to an increase in the effective grain size of the GBF and AF and a decrease in the density of dislocations, as well as promoted the precipitation of nanoscale particles; however, the overall yield strength decreased slightly. The increased N content also resulted in an increased amount of M/A constituent, which improved the overall strain-hardening capacity of the microstructure of GBF+AF/M/A, and resulted in an elevated tensile strength and a simultaneously lowered yield-to-tensile strength ratio. In addition, the mechanisms governing the effect of increased N in controlling the final microstructure and tensile properties were discussed.