Effect of Initial Austenite Grain Size on Microstructure Development and Mechanical Properties in a Medium-carbon Steel Treated with One-step Quenching and Partitioning
Effect of Initial Austenite Grain Size on Microstructure Development and Mechanical Properties in a Medium-carbon Steel Treated with One-step Quenching and Partitioning
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DOI：
10.2355/isijinternational.isijint-2020-543
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发表时间：
2021-02
影响因子：
1.8
通讯作者：
T. Tsuchiyama;Y. Amano;Shohei Uranaka;T. Masumura
中科院分区：
文献类型：
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作者：
T. Tsuchiyama;Y. Amano;Shohei Uranaka;T. Masumura
Fe-0.4C-1.2Si-0.8Mn（质量%）合金在1 103 ~ 1 473 K的不同温度下奥氏体化，在473 K时进行中断淬火（IQ），然后在该温度下保持，诱导碳从马氏体向奥氏体分块（一步淬火和分块（Q & P）过程）。IQ前奥氏体的初始晶粒尺寸为20 ~ 573 μ m，随着初始晶粒尺寸的细化，分配过程中未转化奥氏体中碳的富集程度增强，导致残余奥氏体体积分数增大。马氏体/奥氏体界面面积的增加导致了碳的有效分配和贝氏体相变的加速，从而导致了碳富集的增加。对具有不同初始奥氏体晶粒尺寸的试样进行拉伸试验，结果表明，通过初始奥氏体晶粒的细化，一步法Q和P试样的力学性能在强度和伸长率方面都得到了改善。
Fe-0.4C-1.2Si-0.8Mn (mass%) alloys austenitized at different temperatures, ranging from 1 103 to 1 473 K, were subjected to interrupted quenching (IQ) at 473 K and then maintained at that temperature to induce the partitioning of carbon from martensite to austenite (one-step quenching and partitioning (Q & P) process). The initial austenite grain size before the IQ was varied from 20 to 573 μ m. As the initial austenite grain size becomes finer, the enrichment of carbon in the untransformed austenite during the partitioning treatment is enhanced, which leads to a greater increase in the volume fraction of retained austenite. The reasons for the increased carbon enrichment were explained by the effective carbon partitioning as well as the promoted bainitic transformation, which were both caused by the increase in the area of the martensite/austenite interface. Tensile tests of the specimens with different initial austenite grain sizes revealed that the mechanical properties of the one-step Q & P specimens improved in both strength and elongation by the refinement of the initial austenite grains.