Study On Fabrication And Mechanical Properties For Bimetal Using Spray-forming Al-22Si/Cast Aluminum

With the engine lightweight and high performance requirements,it is imperative to develop new lightweight materials that not only have good casting properties but also have high mechanical properties and wear resistance.Spray-formed high silica aluminum alloy has good performance,such as specific strength,thermal stability and wear resistance.Therefore,Sprayformed high-silicon aluminum alloy has a wide range of applicationswiththedevelopment of engineengine liner.However,high silicon aluminum alloy with poor casting and poor plasticity,limiting its promotion and use.Among them,bimetallic aluminum alloy effectively solve the above contradiction,and become a hot research.In this paper,the goal is the development of spray-formed Al22Si5Fe3Cu1 Mg alloy as the matrix of bimetallic materials.The microstructure and wear resistance of the alloy were studied and the gravity casting and extrusion casting processare were used to prepare bimetallic materials.The spray-formed Al22Si5Fe3Cu1 Mg alloy was used as the research object,the mechanical properties and the microstructure of the alloy were studied.At the same time,the effects of friction behavior and wear mechanism for high-silicon aluminum alloy at different temperatures is systematically studied by comparing two processes of conventional casting and spray-formed for manufacturing Al22Si5Fe3Cu1 Mg alloy.The results show the silicon phase size of spray-formed Al22Si5Fe3Cu1 Mg alloy can be effectively refined,and the mechanical properties of Al22Si5Fe3Cu1 Mg alloy are greatly improved compared with conventional casting.The tensile strength is 402 MPa at room temperature,and the tensile strengthcan reach 280 MPa at 300 ℃,this indicating that the alloy has good thermal stability.The wear result shows that Al22Si5Fe3Cu1 Mg alloy using spray-form process shows better abrasion and wear properties due to its characteristics finer grain and uniform composition compared with that using conventional casting.The results show that wear mechanism changed with temperature,which show mixed wear of abrasive and adhesive when lower than the critical temperature and show delamination wear when higher than the critical temperature.When explored at high temperature,the formation of oxidation improved the wear resistance for the Al22Si5Fe3Cu1 Mg alloy due to the fast oxidation and there exiting a critical temperature which wear increased significantly.The wear mechanism of two materials changed into delamination wear with wear rate increased dramatically from low wear.Notably,the Al22Si5Fe3Cu1 Mg alloy with spray-formed process shows superior wear resistance than that from conventional cast both at high and low temperatures.Moreover,the Al22Si5Fe3Cu1 Mg alloy with sprayformed process has higher critical temperature of wear mechanism than that with conventional cast.The wear resistance performance of the spray-formed Al22 Sialloy was better than that of cast iron,and its wear loss presented an approximately linear relationship with the sliding distance.Initially,the spray-formed Al-22 Si alloy was extremely worn due to an abrasive action on the sharp particles and the fracture of the larger particles.Once the sharp edges of the abrasive became blunt with the wear progress,the degree of wear and tear decreased dramatically.This research investigated the effects of surface treatment and appropriate gating system on the microstructures and mechanical properties for evaluating the optimal strategy for producing high quality bi-metal materials.The bi-metal materials were prepared by ZL104 gravity casting by different pouring type around the spray-formed Al-22 Si with varied surface treatments.The wettability between Al22 Si and ZL104 was significantly improved when Zn coating was used to remove the natural oxide layer.This research also obtained the improved interfacial microstructures and interfacial bonding strength for materials when applied the appropriate pouring type.The properties and fracture behaviors of different surface treatments between oxide film and zinc coating were compared between the Al22 Si and Zl102 bimetal through extrusion process.Bimetal alloy was prepared by spray-formed Al22 Si alloy and ZL102 through extrusion process under solid-solid state,semi-solid state and solid-liquid state.During the process of extrusion under solid-solid state,the oxidation film was extruded to crush and the metal was extruded though the micro-cracks of the oxidation film,then the two surfaces were joined together.The average bonding strength of bimetal with intermittent oxide film interface is higher than that of the bimetal fabricated by zinc coating.The results showed that sound metallic bonding could be produced through the semi-solid extrusion process.The bimetal through semi-solid extrusion bonding process is the oxide film is broken by hard particles,the liquid metal wrapped with hard particles to achieve a perfect connection.With the semi-solid extrusion process,the tensile strength exhibits more promising results than that made solid-solid combination and solid-liquid combination.The average bonding strength of the interface could reach about 120 MPa,some of which fracture in ZL102 alloy.The process presented in this study provides a promising and effective approach for achieving a high-quality metallurgical bonded interface to manufacture Al22Si/Zl102 bimetal.