Study On Preparation And Microstructure & Properties Of Aluminum Matrix Composite Reinforced By Fiber Copper (T2) Mesh

In recent years,the aluminum matrix composite prepared by ARB technology has been widely used in military,aviation,aerospace and civil fields because of its high specific strength,low density,high thermal conductivity and other excellent comprehensive properties.At present,many researchers have successfully prepared a large number of aluminum matrix composites with SiC particles,Cu particles,carbon fibers,Al₂O₃ fibers and steel wire mesh as reinforcements by using ARB technology.However,during the rolling process,the appearance of reinforcement particles clusters,interface pores,deformation incongruity and grid distribution not dense will hinder reinforcement effect.In this thesis,a kind of compact（350 mesh）fiber copper（T2）mesh woven by orthogonal method is selected as the reinforcement,and the best process of preparing aluminum matrix composite with copper grid reinforced by ARB technology is explored by cold rolling&cumulative rolling（ARB）,hot rolling&cumulative rolling（ARB）,changing the laying angle of copper mesh and heat diffusion treatment.The mechanical properties of Al/Cu composite plates with different cycles were tested by means of uniaxial tension and microhardness,and the macrostructure and microstructure of composite plates were analyzed by SEM,EDS,TEM and XRD.The results show that tensile strength and elongation of Al/Cu composite plate are 171 MPa and 5.39%respectively after 5 passes of cold rolling,and they increase with the increasing of rolling passes.It can be seen that the introduction of copper mesh as reinforcement is a new way to improve the strength and plasticity of aluminum matrix composite at the same time.The thickness increased from 4.63μm to 6.09μm,which greatly promoted the interface bonding strength of composite plate.TEM observation showed that the Al grains were mainly long strip structure,and grain size was obviously refined from 1.17μm（0 cycle）to 0.64μm（5 cycle）,indicating that fine grain strengthening mechanism was the main strengthening mechanism of high cycle composite plate;After 5 passes of rolling,the hardness of Al layer and Cu layer increased to maximum value,which was 51.18 HV and 205.1 HV respectively.There were different sizes of shear dimples on the fracture surface of composite plate,indicating that the fracture mechanism was typical shea r ductile fracture.The results show that,when the laying angle of copper mesh is 45°,tensile strength and elongation of aluminum copper composite plate reach the maximum value after four rolling passes in the hot rolling process,which are 174.1 MPa and15.2%,respectively.When the laying angle of copper mesh is 0°,the tensile strength and elongation of the aluminum copper composite plate reach a good strong plastic match after three rolling passes,the strength is 147.3 MPa,and the elongation is 7.5%.It can be considered that the tensile strength and elongation of fiber copper mesh reinforced aluminum composite increase with the increasing of copper mesh laying angle.The fracture morphology shows that the fracture mode of Al/Cu composite plate is mainly plastic fracture form in Al layer and interface delamination fracture in Al/Al interface.The in-situ tensile tests results of cold-rolled and hot-rolled composite plates show that interface bonding between base metal aluminum plates can be realized under same rolling deformation by 25℃cold rolling and 400℃hot rolling condition.In-situ tensile load displacement curves of composite plates under two rolling conditions show obvious elastic stage,plastic stage and failure stage.The results show that the cold rolling at 25℃has better comprehensive properties,and its ultimate load and maximum displacement are 217 N and 2.16 mm respectively.Dynamic observation of fracture process shows that microcracks are initiated around the Cu particles and at the stress concentration,and continue to grow and connect with each other at the Al/Cu interface.Main cracks expand rapidly with the tensile load until obvious fracture occurs,and the fracture path is 45°along slip line and uniaxial tensile direction.Fracture analysis shows that failure modes of cold-rolled and hot-rolled composite plates are the whole ductile delamination fracture and the ductile shear fracture of Al layer and Cu layer.