Key Characteristics of Hypereutectic Al-Si alloy
Low coefficient of thermal expansion(CTE);lower weight;dimensional stability;higher thermal conductivity;excellent wear-resistance and corrosion resistance.The hypereutectic Al-Si alloy possess these combination performances which extremely suitable for manufacturing lightweight and wear-resistance parts.
The properties of hypereutectic Al-Si alloy,encompassing the casting performance,mechanical property,abrasion property and cutting machining.
A large amount of latent heat is released when the primary silicon precipitate out,the commonly used eutectic al-si alloy has better fluidity than eutectic alloy.However, liquidity will begin to decline after the Si content exceeds 18%. As the silicon content in the alloy increases, the linear shrinkage decreases.While with the expansion of the crystallization temperature range, some casting defects will gradually appear, such as alloy shrinkage tendency increases, reduced air tightness, that is, casting performance.
The alloys can obtain the satified mechanical properties if through the matchable modification.As the temperature increases,the alloy strength reduction but improve the ductility. Under the condition of select suitable composition and modification treatment,the high temperature strength of hypereutectic Al-Si alloy is superior than that of eutectic alloy.
As the increase of silicon content,the primary silicon volume percentage will increase in the alloy,so that improve the abrasion resistance of the alloy.
Comparation to the cocrystallizing type and eutectic alloy, the wear rate of hypereutectic of Al-Si alloy is 0.3~0.5 times than hypoeutectic alloy,is 0.1~0.2 times than that of eutectic alloy.In general,the hypereutectic Al-Si alloy has excellent wear-resistance property.
Owing to the tool is worn very easily and roughness surface.The solution to this problem is to use the diamond tools,or add a little lead(Pb) or bismuth(Bi) in the alloy composition.
High Temperature Strength and Dimensional Stability
The current research focuses on the hypereutectic alloys with silicon content below 30%. Due to its high thermal conductivity and controllable thermal expansion coefficient, high-silicon aluminum alloys are used in electronic packaging materials,e.g 27Si-73Al to 70Al-30Al controlled expansion alloys.
Currently,Erbslöh Aluminium GmbH has fabricated range of hypereutectic Al-Si alloy products and successfully entered into mass-production stage,e.g.crankcase.measurement technology,oil pump gears,connecting rods and bearing caps etc.In Japan,more and more manufacturers prefer to select the hypereutectic Al-Si alloy as the raw material of pistons,and expand the application to the trucks and commercial vehicles.
Though the hypereutectic Al-Si alloy is still in the state of research and development in China,Tianjin Baienwei New Material Technology Co.,Ltd as an individual large scale high-tech company which has produced series of aluminum alloy products,e.g.advanced pistons and cyliner sleeves,which have reached the world level standard.The products manufactured has recognized by our clients in the Germany and North America.Baienwei Co.Ltd stick to the principle of ‘’Technological innovation and rejuvenate the state by industrialization’’.We serve our markets with both standard products and customized driven products and milling CNC machining service.Through years of great effort,significant progress has been made in the development of automotive assembly parts.