Study Of Microstructure And Mechanical Properties On Al/Cu Multilayer Composites

The various monopropellant nano and ultrafine grained(UFG) metal materials had been successfully prepared by accumulative roll bonding(ARB) technology. In recent years, however, The study that metallic multi-layered composites(LMCS) of bimetal systems was produced by the ARB technology also gradually increased. In the process of ARB technology applied to produce dissimilar metallic multi-layered composites, whose accumulative roll bonding process was only limited to regard one phase as a matrix, another phase materials as a strengthening phase uniformly dispersed in the dissimilar metallic multi-layered composites, due to the hard phase layers in the process of accumulative roll bonding necking and subsequently fracturing. In order to improve the situation, This paper developed a modified accumulative roll bonding process which was based on conducting 300℃/0.5 h intermediate annealing before each accumulative roll bonding cycle to successfully fabricate Al/Cu multi-layered composites whose the distribution of each layer metal materials was uniform and continuous, then Al/Cu multi-layered composites were continually rolled by 50% of the conventional rolling at room temperature. Metallographic microscope, SEM, EDS, XRD, TEM and tensile testing machine were employed to analysis macrostructure and microstructure and the mechanical properties of ARBed Al/Cu multi-layered composites and cold-rolled(CRed) Al/Cu multi-layered composites, respectively.For different cycled ARBed Al/Cu multi-layered composites showing: In observing different cycled ARBed Al/Cu multi-layered composites samples, the distribution of each layer of ARBed Al/Cu multi-layered composites was keeping good uniformity and continuity. After 8 cycles of the ARB process, Thicknesses of Al and Cu layers were 500 um ~1.9 μm and 1000 μm ~4.17 μm, meanwhile the deformations were ~99.62% and ~99.58%, respectively. In the process of conducting 300℃/0.5 h intermediate annealing before each accumulative roll bonding cycle, Al and Cu atoms of Al/Cu interfaces had had the mutual diffusion, and in the Al/Cu interfaces had formed intermetallic compounds. By increasing the number of cycles of the ARB process, the strength of ARBed Al/Cu multi-layer composites was gradually increasing and elongation of it was gradually decreasing. After 8 cycles of the ARB process, the yield strength(YS) increased to 354.7 MPa and tensile strength(TS) increased to 373 MPa. However, the axial strain was only 0.012 mm/mm.For different layered cold-rolled Al/Cu multi-layered composites showing: In the process of the conventional rolling, the distribution of each layer of cold-rolled 3, 6, 12 layers of Al/Cu multi-layered composites was keeping good uniformity and continuity; each layer of cold-rolled 24, 48, 96 layers of Al/Cu multi-layered composites appeared slight fluctuations, which embodied in the necking of Cu layer; and the fluctuation of each layer of cold-rolled 192, 384 layers of Al/Cu multi-layered composites was obvious, which manifested the necking of Al layer. As the increasing of the number of layers cold-rolled Al/Cu multi-layered composites, the number of intermetallic compounds of Al/Cu interfaces was growing and obviously grew up. TEM photographs showed that each layer of cold-rolled 96 layers of Al/Cu multi-layered composites contained a multitude of dislocation cell structures, then fitted by XRD analysis, As the increasing of the number of layers cold-rolled Al/Cu multi-layered composites, the dislocation density of it increases unceasingly, the dislocation density of cold-rolled 384 layers of Al/Cu multi-layered composites had up to ~2.0×1014 m-2. Meanwhile strength of cold-rolled Al/Cu multi-layered composites is gradually increasing, tensile strength of cold-rolled 384 layers of Al/Cu multi-layered composites increased to ~403 MPa, However, its total elongation was only 1.8%. After the tensile test, Observation revealed that the fracture mode of Al and Cu layers of cold-rolled Al/Cu multi-layered composites was a shear ductile fracture, however, the fracture mode of intermetallic compounds of Al/Cu interfaces to was typical brittle fracture.