Microstructures And Mechanical Properties Of Mg/Al Multilayered Composite Sheets Fabricated By Furnace Heat-assisted Or Electrically-assisted Accumulative Roll Bonding

Pure magnesium and magnesium alloys have good damping properties,high specific strength and specific modulus of elasticity,but there are problems of corrosion and low strength.Pure aluminum and aluminum alloys generally have better formability and corrosion resistance than magnesium.The accumulative roll bonding process is used to fabricate Mg/Al multilayered composites,which can combine the advantages of Mg and Al to obtain excellent comprehensive mechanical properties and better corrosion resistance.However,due to the complicated fabricate process and the formation of intermetallic compounds in the Mg/Al interface,the interface bonding is seriously affected,and the Mg/Al multilayered composites fabricated by the accumulative roll bonding does not obtaine good mechanical properties,and the increase in tensile strength is relatively low.Furnace heat and electrically-assisted accumulative roll bonding process was utilized to explore the feasibility of improving the strength of Mg/Al multilayered composite sheets by high number of rolling cycles and the electrically-assisted accumulative roll bonding effect on the intermetallic compounds.Specifically,the Mg/Al multilayered composite sheets was fabricated by the furnace heat accumulative roll bonding process.The microstructure of the multilayered composite sheet was characterized by SEM and EDS.The tensile test and the microhardness test were carried out on the samples.The strengthening mechanism of the furnace heat acucumulative roll bonding Mg/Al multilayered composite sheets was discussed.The conventional furnace heat was replaced by using electrically-assisted heat.By comparing the traditional heat treatment and the electrically-assisted accumulative roll bonding process,the effects of electrically-assisted rolling on the microstructure and mechanical properties of the samples and the inhibition of intermetallic compounds were investigated.The results show that:(1)The mechanical properties of the sample can be significantly improved by the furnace heat accumulative roll bonding process after high number of rolling cycles.After 7 cycles of accumulative roll bonding,a Mg/Al multilayered composite sheet with a layer thickness of micron was fabricated,and the sample strength increased significantly with the increase of the rolling cycles.A diffusion layer and interfacial intermetallic compound between the Mg/Al layers was formed.As the number of rolling cycles increases,the thickness of the diffusion layer gradually increases,and after 7 rolling cycles,the interfacial intermetallic compound dispersed at the interface of Mg and Al was formed.(2)The Mg/Al multilayered composite sheets were fabricated by electrically -assisted accumulative roll bonding,and the growth of the intermetallic compound is effectively inhibition.After electrically-assisted rolling,the Mg/Al multilayered composite were bonded well,and the growth of the intermetallic compounds were effectively suppressed.The electrically-assisted process effectively suppressed the growth of the intermetallic compound during the rolling process,and the thickness of the intermetallic compound formed at the interface is significantly lower than that of the conventional Furnace heat accumulative roll bonding.