Effect of carbon content on formation of bimodal microstructure and mechanical properties of low-carbon steels subjected to heavy-reduction single-pass hot/warm deformation
Effect of carbon content on formation of bimodal microstructure and mechanical properties of low-carbon steels subjected to heavy-reduction single-pass hot/warm deformation
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DOI：
10.1016/j.msea.2014.04.011
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发表时间：
2014-06
期刊：
影响因子：
6.4
通讯作者：
Hyung-Won Park;J. Yanagimoto
中科院分区：
文献类型：
--
作者：
Hyung-Won Park;J. Yanagimoto
通过模拟大压下量单道次轧制的压缩试验，研究了0.01%和0.1%碳钢及铌钢在双态组织形成过程中的组织演变及力学性能。当形变热处理进行附近和以上的临界转变温度（Ac3），所有钢的显微组织显着细化，由等轴晶粒没有拉长的晶粒。然而，这些显微组织显示出弱或没有形成的双峰结构或粗晶粒随着碳含量的降低，而它们显示双峰结构形成时，0.2%的碳钢在我们以前的研究中使用。Nb钢的平均晶粒尺寸约为2 μm，组织均匀细化。这可能是由于随着低碳钢中碳含量的降低，形核位点的数量减少，以及加工过程中Nb钢在晶界和晶粒内部发生形核。在临界转变温度以上变形的所有钢的机械性能表现出高性能特征，具有上级强度和显著的延伸率。拉伸试验后的扫描电镜观察表明，其断口为韧性断裂。
A compression test simulating heavy-reduction single-pass rolling was conducted to investigate the microstructural evolution based on the formation of a bimodal structure and the mechanical properties of 0.01% and 0.1% carbon steels and niobium steel. When thermomechanical processing was conducted near and above the critical transformation temperature (Ac3), microstructures of all steels were significantly refined and consisted of equiaxed grains without elongated grains. Nevertheless, these microstructures showed weak or no formation of the bimodal structure or coarse grains with decreasing carbon content, while they showed bimodal structure formation when 0.2% carbon steel was used in our previous research. The average grain size of Nb steel was about 2 μm and its microstructure was uniformly refined. These may be attributed to a decrease in the number of nucleation sites with decreasing carbon content in low-carbon steels and the occurrence of nucleation at grain boundaries as well as in grain interiors in Nb steel during processing. Mechanical properties of all steels deformed above the critical transformation temperature exhibited high performance characteristics with superior strength and marked elongation. Their fractographs indicated ductile fracture, which was revealed by SEM observation after a tensile test.