Abstract The mechanical properties and fractured behaviors of 0.2C–6Mn–3Al-(0/0.6)Si medium Mn steels, denoted as 0Si and 0.6Si (0Si without δ-ferrite and 0.6Si with abundant δ-ferrite), are investigated. As the annealing time increases, δ transforms from a hard phase to a soft phase. Due to the hard δ and the weak transformation-induced plasticity (TRIP) effect in 0.6Si, the product of strength and elongation (PSE) is slightly lower in 0.6Si than in 0Si, when the annealing time is less than 7 min. However, the PSE is much higher in 0.6Si than 0Si, resulting from the soft δ and the appropriate TRIP effect in 0.6Si, when the annealing time is higher than 10 min. Microcracks of 0Si initiated at the γ(α')/α interface, and unstable γ could enhance the nucleation and increase the number of microcracks. Microcracks of 0.6Si propagated along the (γ(α') + α)/δ interface, resulting in delamination on fractograph. When the hard δ transformed into soft δ, soft δ abates the plasticity mismatch of the interface, thereby leading to a decrease in the number of interfacial microcracks and delaminations.

中文翻译：

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不同临界间退火时间下含和不含δ铁素体的中锰钢的力学性能和断裂行为

摘要 研究了 0.2C-6Mn-3Al-(0/0.6)Si 中锰钢的力学性能和断裂行为，分别表示为 0Si 和 0.6Si（0Si 不含 δ-铁素体，0.6Si 含有丰富的 δ-铁素体）。随着退火时间的增加，δ从硬相转变为软相。由于 0.6Si 的硬 δ 和弱相变诱导塑性 (TRIP) 效应，当退火时间小于 7 分钟时，0.6Si 的强度和伸长率的乘积 (PSE) 略低于 0Si。然而，当退火时间高于 10 分钟时，0.6Si 的 PSE 远高于 0Si，这是由于软 δ 和 0.6Si 中适当的 TRIP 效应。0Si 微裂纹在γ(α')/α 界面处萌生，而不稳定的γ 可以增强形核并增加微裂纹的数量。微裂纹 0。6Si 沿 (γ(α') + α)/δ 界面传播，导致断口分层。当硬δ转变为软δ时，软δ减弱了界面的塑性失配，从而导致界面微裂纹和分层的数量减少。