Study On The Bonding Process Of 7A52 Aluminum Alloy And Al₂O₃ By Liquid Forming

Metal-ceramic composite materials have been widely used in the field of armor protection because of their high strength,toughness and low density.However,due to the different physical and chemical properties of metal and ceramic materials,it is difficult to connect them.In this paper,the molten 7A52 aluminum alloy metal liquid is injected into a mold containing Al₂O₃ ceramics by liquid forming technology.The 7A52/Al₂O₃ composite material is directly formed after cooling,and the 7A52/Al₂O₃ connection process is studied.The direct joint of 7A52/Al₂O₃ by liquid forming mainly relies on the free spreading of7A52 metal liquid on Al₂O₃ surface.Mg element in 7A52 metal liquid diffuses to solidify at the interface and forms a magnesium rich layer,which can enhance the shear strength of the interface.The wettability of 7A52 metal liquid on the surface of Al₂O₃ can be significantly improved by nickel plating on Al₂O₃,so that the element diffusion is more sufficient.The maximum shear strength can reach 57.40MPa at the preheating temperature of 450?and casting temperature of 750?.Preheating Al₂O₃ ceramics can improve the ceramic fragmentation under the condition of chilling-exciting heat,mainly due to the decrease of temperature difference between preheating and pouring.Proper vacuum heat treatment reduces the residual stress and internal stress of the Ni-P coating.on the one hand,it can reduce the oxidation of the coating during preheating,and on the other hand,it can prevent 7A52 molten metal from instantly dissolving the coating,reacting to form finely divided Al₃Ni phase.After one hour of vacuum heat treatment at 250?,the maximum interfacial shear strength of the coating is 64.45MPa.Excessive heat treatment temperature causes the Ni3P phase to precipitate in the coating.When the subsequent ceramic preheating,the Ni3P phase further precipitates and decomposes,resulting in the formation of unfavorable phases at the connection interface.The shear strength of the coating obtained by vacuum heat treatment at 400?for one hour was only 48.12MPa.The thickness of Ni-P coating and the preheating temperature also affect the interface reaction.When the coating is thin,the interface is composed of?-Al/?-Al+Zinc-rich layer/?-Al+spinel/spinel+Al₂O₃.When the coating is thick,the interface is composed of?-Al/?-Al+Al₃Ni/?-Al+spinel/Al₂O3,and the?-Al+Al₃Ni layer has more adverse reactions.At a low preheating temperature,element expansion is slow,and Mg element is not highly enriched on the ceramic surface.At a high preheating temperature,Mg element is largely enriched on the ceramic surface to form spinel phase.The optimum parameters of 7A52/Al₂O₃(Ni)composite by liquid forming after optimization are:heat treatment at 250?/1h,plating time at 0.5h,preheating temperature at500?,pouring temperature at 750?,and the maximum shear strength at 72.83MPa.