累积复合轧制法制备层状超细晶材料的研究现状

综述了累积复合轧制(ARB)的工艺原理及累积复合轧制材料晶粒的细化机理、力学性能、组织与织构演变特征,分析了目前研究中存在的问题,指出累积复合轧制是制备大块体超细晶金属材料最有效的强烈塑性加工工艺。     

Development of a Heterogeneous Lamellar Structure Based on Layer Instabilities during Accumulative Roll Bonding

The strategy of designing heterogeneous structures has emerged as a new tool in avoiding the prominent strength–ductility trade-off dilemma in metallic materials. However, methods to reproducibly synthesize heterostructured materials with effective microstructural control are still elusive. Herein, a highly reproducible method based on conventional accumulative roll bonding (ARB) and postannealing is proposed for designing heterostructured Cu samples with precisely defined heterogeneous lamellar structure (HLS) wherein the size, volume fraction, and spatial distribution of coarse and fine grains can be accurately controlled. An optimal heterogeneous lamellar microstructure is found which gives rise to a roughly 3 times higher yield strength than that of coarse-grained Cu and a good tensile ductility of ≈34.7% total elongation. Experimental observations reveal that the unique HLS induces strong heterodeformation-induced hardening and promotes dislocation accumulation, leading to the observed exceptional strength–ductility synergy. This novel fabrication method is applicable to a considerably larger number of metal systems and can be utilized to further tailor HLS to optimize the mechanical properties of metals.     

Microstructures and Mechanical Properties of Al/Mg Alloy Multilayered Composites Produced by Accumulative Roll Bonding

Al/Mg alloy multilayered composites were produced successfully at the lower temperature(280 C) by accumulative roll bonding(ARB) processing technique.The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy.Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites.It is found that Vickers hardness,bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass.Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load.Strengthening and fracture mechanisms of the composite are analyzed.     

累积叠轧焊合法制备颗粒增强金属基复合材料的研究现状与展望

近年来,累积叠轧焊合法已经成为制备颗粒增强金属基复合材料的一种新颖工艺。介绍了累积叠轧焊合法制备复合材料的工艺原理,综述了累积叠轧过程中的颗粒增强金属基复合材料的金属基体与增强颗粒固相复合机制、强化机制以及复合材料性能。同时展望了用累积叠轧焊合法制备颗粒增强金属基复合材料的研究趋势。     

累积叠轧制备超细晶纯铜多层板的组织和性能

本工作在室温下采用累积叠轧工艺对纯铜薄板进行1~9道次的大塑性变形加工。采用金相显微镜、双束系统FIB/SEM、TEM及拉伸试验机进行组织观察及力学性能测试,获得纯铜板累积叠轧过程显微组织演变和力学性能演变规律。结果表明:累积叠轧形成的初始界面存在微缝隙和纳米层等缺陷,其中微缝隙随着叠轧的进行而逐渐消失,最终形成冶金界面结合;纳米层由片层厚度为20~60nm的片层晶组成,并包含变形孪晶。在轧辊压缩力与剪切力的共同作用下,原始粗晶晶粒由等轴晶变成片层晶,且发生明显细化,6道次后晶粒片层厚度由退火态的~50μm细化到0.2μm左右;晶粒细化主要以位错滑移分割为主,并伴随少量的孪生;材料的硬度和屈服强度明显提高,9道次后达到最大值,硬度为137HV,约为母材的3倍;屈服强度达450MPa,约为母材的5倍;断裂延伸率在首道次剧烈下降,并在随后道次保持在5%左右。