Continuous-bending-under-tension (CBT) has been conceived as a mechanical test or a forming process imparting cyclic bending during stretching of a metallic sheet or strip in order to increase its elongation to fracture (ETF) relative to simple tension (ST). In a recent work, over five times improved ETF by CBT over ST has been reported for a dual-phase (DP) steel DP 1180. This paper evaluates the behavior in CBT of three additional automotive advanced high strength steels (AHSS), DP 590, DP 780, and DP 980. In doing so, the process parameter space defined in terms of crosshead velocity applying the tensile force, and roller depth imposing the amount of bending to the specimen has been explored to maximize the ETF of these materials. The studied steel sheets had different thicknesses, in addition to intrinsically containing different fractions of ferrite and martensite phases. After establishing the optimal process parameters, significant improvements in ETF are achieved for all studied steels. Based on comprehensive data, it is found that lower martensitic content moderately improves ETF, while increasing of the sheet thickness rapidly deteriorates ETF, under CBT. The behavior in tension of sheets that were subjected to CBT processing under the established optimal process condition is investigated to determine enhancement in strength and any residual ductility of the materials. In addition to testing, a combination of electron microscopy along with electron-backscattered diffraction and neutron diffraction is employed in order to assess the initial microstructure, evolution of crystallographic texture, and fracture mechanisms for the studied steels. Texture evolution in CBT forms a more pronounced {011} fiber along the stretching direction than in ST, revealing that the deformation in CBT could extend to greater strain levels than those reached at the fracture location in ST. Fractured surfaces after CBT are found to consist of fine ductile dimples, while those after ST consist of coarser dimples and some content of brittle flat martensitic regions.

连续拉伸不足（CBT）被认为是一种机械测试或一种成形工艺，在拉伸金属片材或带材的过程中赋予循环弯曲以相对于简单张力（ST）增加其断裂伸长率（ETF） 。在最近的一项工作中，已经报道了双相（DP）钢DP 1180的CBT改性后的ETF比ST改性的ETF高出五倍。本文评估了另外三种汽车高级高强度钢（AHSS）DP 590的CBT行为。 ，DP 780和DP980。在此过程中，已探索了根据施加拉力的十字头速度和施加于试样弯曲量的辊深度定义的工艺参数空间，以使这些材料的ETF最大化。所研究的钢板具有不同的厚度，除了本质上包含不同比例的铁素体和马氏体相。在确定最佳工艺参数后，所有研究钢材的ETF均获得了显着改善。根据综合数据，发现在CBT条件下，较低的马氏体含量会适度地改善ETF，而薄板厚度的增加会迅速使ETF劣化。在确定的最佳工艺条件下，对经过CBT处理的板材的张力行为进行了研究，以确定强度的增强和材料的任何残余延展性。除了测试外，还结合使用电子显微镜，电子反向散射衍射和中子衍射来评估初始微观结构，晶体织构的演变，和研究钢的断裂机理。CBT中的纹理演变沿拉伸方向比ST中形成更明显的{011}纤维，这表明CBT中的变形可能会延伸到比ST中的断裂位置处更大的应变水平。发现CBT后的断裂表面由细小的延性凹痕组成，而ST后的表面由较粗的凹痕和一些脆性的平坦马氏体区域组成。