Study On Fatigue And Tensile Properties Of Metal Laminated Materials

With the rapid development of MEMS,the reliability of metal laminated composites which are widely used in MEMS becomes very important,more and more attention has been paid to the mechanical behavior of metal laminated composites.Therefore,the fatigue and tensile properties of metal laminated composites were studied by using Cu;IF steel and 6061 aluminum alloy as model materials in this thesis,the fatigue and tensile properties of metal laminated composites were studied by theoretical simulation and experimental process,respectively.The results are as follow:(1)Based on molecular dynamics simulation,the structure models of three kinds of Cu,Fe and Al single crystals were established.The tensile deformation behavior of three kinds of metallic single crystals was studied.The elastic modulus of Cu,Fe and Al was calculated to be 78 GPa;228 GPa and 69 GPa,respectively.(2)Using copper and IF steel as experimental specimen,the annealed polycrystalline copper foils with different thickness(t=70?200 ?m)were prepared by electrolytic etching method and the annealed IF steel foils with different rolling elongation(?=2857%;6667%;10000%)were prepared by multi-pass cold rolling.It was studied that the cantilever beams fatigue and damage behavior of the copper and IF steel foils under the control of total cyclic strain amplitude.The results showed:(a)when the thickness of copper foil is greater than 100 ?m,there was little effect on the fatigue life of copper foil for the material geometry.Under the same cyclic strain amplitude,the bending fatigue life of copper foils is higher than that of bulk Cu and Cu thin films,and the surface of Cu foils eventually fractured due to fatigue damage caused by extrusion/invasion and crack along grain boundary;(b)the dimensionless rolling deformation factor was proposed and the relation between the rolling deformation factor of fatigue life and external service condition was established.The deformation behavior of IF steel foil under total strain control was studied,which under the same cyclic strain amplitude,the tensile strength and fatigue life of IF steel foil decreased gradually with the increase of rolling elongation.The larger the cyclic strain amplitude applied,the smaller the rolling deformation factor.(3)The Al/Al double layered composite and Al/CR340/Al sandwich metallic laminated composites were prepared by Accumulated Roll Bonding(ARB)with 6061 aluminum alloy steel and CR340 steel as experimental specimen.It was researched that the impact of solution and aging treatment on the microstructure and mechanical performance of metal laminated composites.The physical essence of the contribution of aluminum and steel components to the mechanical properties of metal laminated composites was explored.It was showed that compared with the Al/Al double-layer composite,the strength and ductility of the metal laminated composite with the addition of CR340 steel component was both higher.When the solution temperature was 540 ?,the solution time was 1 h,the aging temperature was 165 ?,and the aging time was 6 h,the mechanical properties such as yield strength,tensile strength and elongation at break of metallic layered materials were good as a whole.