硅和铬对超高强双相钢组织和性能的影响

 利用热膨胀仪研究了合金元素硅和铬对C-Si-Mn-Nb系与C-Cr-Mn-Nb系超高强双相钢连续冷却相变规律的影响；采用单向拉伸试验，以及OM、SEM和TEM等方法对比研究了2种DP钢的组织性能与断口形貌。结果表明：硅元素能够提高Ac1]和Ac3]点温度，扩大两相区，促进铁素体相变，并能提高马氏体的回火稳定性，改善其形貌和分布；铬元素的添加导致了奥氏体中碳的分布不均匀，使得马氏体内部同时出现了孪晶与板条状精细结构，而且快冷过程中出现了残余奥氏体和马奥岛组织，部分马氏体会在时效过程中发生分解；两钢的抗拉强度均超过1 000 MPa，伸长率超过15%，且含硅的双相钢各项力学性能均要优于含铬的双相钢。

Effects of Si and Cr on microstructure and mechanical properties of ultra high strength dual-phase steel

The effects of Cr and Si on the transformation of C-Cr-Mn-Nb and C-Si-Mn-Nb ultra-high strength dual phase steels were analyzed by using thermal dilatometer. The microstructure properties and the fracture surfaces of the steels were tested by tensile tests， optical microscopy， scanning electron microscopy and transmission electron microscope. The results show that the addition of Si can increase the temperature of Ac1]andAc3]， enlarge the two phase region， promote the ferrite transformation， increase the aging stability of martensite and improve its morphology and distribution; the addition of Cr leads to the uneven distribution of C in austenite， the appearance of lamellar and parallel twin microstructure， as well as the appearance of residual austenite and the M/A in the fast cooling stage and the decomposition of some martensite in overaging stage. Although tensile strength and elongation of the two steels both exceed 1 000 MPa and 15% respectively， the comprehensive mechanical properties of DP steel containing Si are superior to that containing Cr.