The effect of ultrasonic surface rolling process on tensile properties of a novel Fe-0.6C-2.0Al-1.5Mn-0.04 Nb quenching-partitioning-tempering steel was investigated. Optical microscope, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy were brought out to characterize the microstructure. Compared with quenching-partitioning-tempering steel, the strength and plasticity of the ultrasonic rolling specimen were increased simultaneously, reaching 1329.1MPa and 23.6%, respectively, and the product of strength and elongation reached the range of the third generation Advanced High Strength Steels. The plasticity improvement mechanism of the USRP1specimen is mainly stemmed from two aspects: First, obvious strain gradients during the tensile process was found in the USRP specimens, which not only avoids the strain localization, but also generates a biaxial stress state. The geometrically necessary dislocations induced by the strain gradient and the dislocations induced by the biaxial stress state promoted extra work hardening, thus ensuring high plasticity of the material. Second, there was a moderate content and small size of twinned martensite in the USRP1 specimen. The improvement in yield strength of the USRP specimens primarily results from grain refinement strengthening, dislocation strengthening, phase transformation strengthening, and back stress strengthening. Among them, phase transformation strengthening contributed the most.

中文翻译：

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超声波滚压对高碳低合金调质钢拉伸性能的影响

研究了超声波滚压工艺对新型Fe-0.6C-2.0Al-1.5Mn-0.04 Nb调质钢拉伸性能的影响。采用光学显微镜、扫描电子显微镜、X射线衍射和透射电子显微镜对微观结构进行表征。与调质钢相比，超声波滚压试样的强度和塑性同时提高，分别达到1329.1MPa和23.6%，强度和延伸率乘积达到第三代先进高强度钢的范围。USRP1试件的塑性改善机制主要源于两个方面：首先，USRP试件在拉伸过程中发现了明显的应变梯度，这不仅避免了应变局部化，而且产生了双轴应力状态。应变梯度引起的几何必要位错和双轴应力状态引起的位错促进了额外的加工硬化，从而保证了材料的高塑性。其次，USRP1 试样中存在含量适中、尺寸较小的孪生马氏体。USRP试样屈服强度的提高主要来自晶粒细化强化、位错强化、相变强化和背应力强化。其中，相变强化贡献最大。