经冷轧和热处理的钢板,按重量百分比计,其具有包含以下的组成:0.10%≤C≤0.40%,3.5%≤Mn≤8.0%,0.5%≤Si≤2.5%,0.003%≤Al≤3.0%,其中Si+Al≥0.8%,0.001%≤Mo≤0.5%,S≤0.010%,P≤0.020%,N≤0.008%,以及任选的选自Cr、Ti、Nb、V和B中的一种或更多种元素,使得:0.01%≤Cr≤2.0%,0.010%≤Ti≤0.080%,0.010%≤Nb≤0.080%,0.010%≤V≤0.30%,0.0005%≤B≤0.003%,组成的剩余部分为铁和由熔炼产生的不可避免的杂质。以表面分数计,所述钢板的显微组织由10%至50%的残留奥氏体、至多8%的新鲜马氏体,以及回火马氏体组成。残留奥氏体包括:‑Mn含量高于1.3*Mn%的富Mn奥氏体,Mn%表示钢板的Mn含量,所述富Mn奥氏体相对于整个显微组织的表面分数为2%至12%;以及‑Mn含量为0.5*Mn%至1.3*Mn%的贫Mn奥氏体。
Cold-rolled and heat-treated steel sheet, having a composition comprising, by weight percent: 0.10% ≤ C ≤ 0.40%, 3.5% ≤ Mn ≤ 8.0%, 0.5% ≤ Si ≤ 2.5%, 0.003% ≤ Al ≤ 3.0%, with Si+Al ≥ 0.8%, 0.001% ≤ Mo ≤ 0.5%, S ≤ 0.010%, P ≤ 0.020%, N ≤ 0.008%, and optionally one or more elements selected from amongst Cr, Ti, Nb, V and B, such that: 0.01% ≤ Cr ≤ 2.0%, 0.010% ≤ Ti ≤ 0.080%, 0.010% ≤ Nb ≤ 0.080%, 0.010% ≤ V ≤ 0.30%, 0.0005% ≤ B ≤ 0.003%,the remainder of the composition being iron and unavoidable impurities resulting from the smelting. The microstructure consists of, in surface fraction, between 10% and 50% of retained austenite, at most 8% of fresh martensite, and tempered martensite. The retained austenite comprises:- Mn-enriched austenite, having a Mn content higher than 1.3*Mn%, Mn% designating the Mn content of the steel sheet, the surface fraction of said Mn-enriched austenite with respect to the whole microstructure being comprised between 2% and 12%, and- Mn-poor austenite, having an Mn content comprised between 0.5*Mn% and 1.3*Mn%.