Strain hardening by dynamic slip band refinement in a high-Mn lightweight steel
Strain hardening by dynamic slip band refinement in a high-Mn lightweight steel
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DOI：
10.1016/j.actamat.2016.06.037
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发表时间：
2016-09
期刊：
影响因子：
9.4
通讯作者：
E. Welsch;D. Ponge;S. M. H. Haghighat;S. Sandlöbes;P. Choi;M. Herbig;S. Zaefferer;D. Raabe
中科院分区：
文献类型：
--
作者：
E. Welsch;D. Ponge;S. M. H. Haghighat;S. Sandlöbes;P. Choi;M. Herbig;S. Zaefferer;D. Raabe
采用电子通道对比成像（ECCI）和透射电子显微镜（TEM）研究了高mn轻钢（Fe-30.4Mn-8Al-1.2C (wt%)）的应变硬化机制。该合金具有恒定的高应变硬化率，同时具有高强度和高延展性（极限抗拉强度：900 MPa，断裂伸长率：68%）。研究不同应变水平下的变形组织，以揭示和量化微纳米尺度上的控制结构参数。由于材料的变形主要是由平面位错滑移引起的滑移带的形成，我们定量地研究了滑移带间距在应变过程中的演变。在通过应力的基础上，根据滑移带间距计算流动应力。计算值与拉伸试验数据吻合较好，表明动态滑移带细化是主要的应变硬化机制，具有优异的力学性能。这种新的应变硬化机制是基于共面滑移带之间的传递应力，而不是先前试图解释基于微带晶粒细分的高mn轻钢的应变硬化。我们详细讨论了均匀分布的滑移带的形成和滑移带间距的逐渐减小，从而导致持续的高应变硬化。对淬火态析出态的透射电镜研究显示，晶粒尺寸< 2 nm，具有精细分散的原子有序团簇。讨论了这些带对平面滑移的影响。
The strain hardening mechanism of a high-Mn lightweight steel (Fe-30.4Mn-8Al-1.2C (wt%)) is investigated by electron channeling contrast imaging (ECCI) and transmission electron microscopy (TEM). The alloy is characterized by a constant high strain hardening rate accompanied by high strength and high ductility (ultimate tensile strength: 900 MPa, elongation to fracture: 68%). Deformation microstructures at different strain levels are studied in order to reveal and quantify the governing structural parameters at micro- and nanometer scales. As the material deforms mainly by planar dislocation slip causing the formation of slip bands, we quantitatively study the evolution of the slip band spacing during straining. The flow stress is calculated from the slip band spacing on the basis of the passing stress. The good agreement between the calculated values and the tensile test data shows dynamic slip band refinement as the main strain hardening mechanism, enabling the excellent mechanical properties. This novel strain hardening mechanism is based on the passing stress acting between co-planar slip bands in contrast to earlier attempts to explain the strain hardening in high-Mn lightweight steels that are based on grain subdivision by microbands. We discuss in detail the formation of the finely distributed slip bands and the gradual reduction of the spacing between them, leading to constantly high strain hardening. TEM investigations of the precipitation state in the as-quenched state show finely dispersed atomically ordered clusters (size < 2 nm). The influence of these zones on planar slip is discussed.