TWIP钢/IF钢热轧复合板材的微观结构和界面结合性能

Microstructure and Interfacial Bonding Property of a Hot-roll-bonded TWIP/IF Steel Composite Plate

界面结合可靠性是影响层状复合板材力学性能的重要因素。采用热轧复合和退火工艺制备TWIP钢/IF钢/TWIP钢三层复合板材,通过拉剪试验、显微硬度测量、结合界面周围合金元素分布的定量分析、变形前后微观组织表征,研究层状复合板材的结合界面形成、界面结合可靠性以及层间剪切变形行为。结果表明:复合板材的相邻层之间形成平均宽度约12μm的界面结合区域,其内部包含片条状马氏体组织,且该薄层区域的硬度显著高于两侧TWIP钢和IF钢的硬度;邻近界面结合区域,主要合金元素C和Mn发生明显重分布。基于上述表征与分析,提出复合板材层间结合界面的形成机制。复合板材的层间结合剪切强度大于IF钢的剪切强度,拉剪试样断裂失效发生在IF钢基体,表明结合界面区域在其两侧分别和IF钢和TWIP钢之间形成良好的冶金结合。拉剪过程中,IF钢良好的塑性变形能力有助于抑制结合界面区域两侧平行微裂纹和结合界面内部垂直微裂纹的形成和扩展。

The reliability of interfacial bonding has a significant impact on the mechanical properties of a laminated composite plate.A three-layered composite plate with the surface layers of twinning-induced plasticity(TWIP)steel and the central layer of interstitial free(IF)steel is fabricated by hot-roll-bonding and annealing processes.Through tensile-shear tests,microhardness measurements,quantitative analysis of alloying elements distributing around the bonding interface,and microstructure characterization before and after deformation,the formation of the bonding interface,the reliability of the interfacial bonding,and the inter-layer shear deformation behavior of the composite plate are investigated.The results are as follows.The bonding interface of the composite plate is essentially a thin-layered region with an average width of approximately 12μm,which mainly contains lamellar martensite structure and has significantly higher hardness than the neighboring TWIP and IF steels.Around the thin interfacial layer,the main alloying elements C and Mn undergo redistribution.A mechanism is then proposed for the formation of the thin interfacial bonding region,based on the above characterizations and analyses.The inter-layer shear strength of the composite plate is higher than the shear strength of the IF steel,and the failure of the tensile-shear specimen takes place in the IF steel matrix,indicating that the interfacial bonding region develops a robust metallurgical bond with both the IF steel and the TWIP steel.During the tensile-shear deformation,the good plasticity of the IF steel contributes to inhibiting the initiation and propagation of parallel microcracks on both sides of the interfacial bonding region and perpendicular microcracks within the interfacial bonding region.