Kim Sung-Dae, Park Seong-Jun, Jang Jae Hoon, Moon Joonoh, Ha Heon-Young, Lee Chang-Hoon, Park Hyungkwon, Shin Jong-Ho, Lee Tae-Ho
Advanced Metals Division, Korea Institute of Materials Science, 797 Changwondaero, Changwon, 51508, Republic of Korea.
Materials and Manufacturing Technology Development Center, Corporate Research and Development Institute, Doosan Heavy Industries and Construction Co. LTD, 22 Doosanvolvo-ro, Changwon, Gyeongnam, 51711, Republic of Korea.
Sci Rep. 2021 Jul 14;11(1):14468. doi: 10.1038/s41598-021-93795-4.
We investigated the effect of κ-carbide precipitates on the strain hardening behavior of aged Fe-Mn-Al-C alloys by microstructure analysis. The κ-carbides-strengthened Fe-Mn-Al-C alloys exhibited a superior strength-ductility balance enabled by the recovery of the strain hardening rate. To understand the relation between the κ-carbides and strain hardening recovery, dislocation gliding in the aged alloys during plastic deformation was analyzed through in situ tensile transmission electron microscopy (TEM). The in situ TEM results confirmed the particle shearing mechanism leads to planar dislocation gliding. During deformation of the 100 h-aged alloy, some gliding dislocations were strongly pinned by the large κ-carbide blocks and were prone to cross-slip, leading to the activation of multiple slip systems. The abrupt decline in the dislocation mean free path was attributed to the activation of multiple slip systems, resulting in the rapid saturation of the strain hardening recovery. It is concluded that the planar dislocation glide and sequential activation of slip systems are key to induce strain hardening recovery in polycrystalline metals. Thus, if a microstructure is designed such that dislocations glide in a planar manner, the strain hardening recovery could be utilized to obtain enhanced mechanical properties of the material.
我们通过微观结构分析研究了κ碳化物析出相对时效态Fe-Mn-Al-C合金应变硬化行为的影响。κ碳化物强化的Fe-Mn-Al-C合金表现出优异的强度-塑性平衡,这得益于应变硬化率的恢复。为了理解κ碳化物与应变硬化恢复之间的关系,通过原位拉伸透射电子显微镜(TEM)分析了时效合金在塑性变形过程中的位错滑移。原位TEM结果证实,粒子剪切机制导致平面位错滑移。在100小时时效合金的变形过程中,一些滑移位错被大的κ碳化物块强烈钉扎,并易于发生交滑移,从而导致多个滑移系的激活。位错平均自由程的突然下降归因于多个滑移系的激活,导致应变硬化恢复迅速饱和。得出的结论是,平面位错滑移和滑移系的顺序激活是诱导多晶金属应变硬化恢复的关键。因此,如果设计一种微观结构,使位错以平面方式滑移,那么应变硬化恢复可用于获得材料增强的力学性能。