Study On Microstructure And Properties Of Squeeze Casting On A390Alloy

In this thesis,the properties of the A390alloy produced by squeeze casting and the modifier for this alloy were deeply studied.A now AlCuP alloy modifier has been developed,which exerts excellent effects on the grain refinement of hypereutectic Al-Si alloys.The mechanical properties and friction and wear properties of squeeze cast A390alloys were tested.The fracture behavior and friction and wear mechanisms of squeeze cast A390alloys were analyzed.The results show that the size of primary silicon was about100μm without modification.When the A390alloy was modified with Cu-8%P alloys,the size of primary silicon was about40～50μm.When the A390alloy was modified with AlCuP alloys,the size of primary silicon was about25～35μm.The modification effect of AlCuP alloys is better than that of Cu-8%P alloys.The alloy performance was largely improved by metamorphism.Squeeze casting is a casting process that the liquid metal was solidified under mechanical stress.The pores、bubbles、segregation and other defects of A390alloy were reduced and the density was raised.The performance of A390alloy was improved.Compared with the alloy produced by metal-mold casting,the vickers hardness of A390alloy by squeeze casting is increased by15.2%;The tensile strength at room temperature is increased by25.2%;The Elongation is less than0.5%,And the tensile strength at300℃of A390alloy is180MPa.At last,the relative wear resistance is1.18times.The room temperature tensile fracture mode of A390alloy is mixed fracture.It contains brittle fracture characteristics of primary silicon and ductile fracture characteristics of Al matrix.Without modification,the main fracture mode of A390alloy is brittle fracture characteristics of primary silicon.Cleavage fracture occurred in the primary silicon.There is transgranular fracture characteristics.When the A390alloy was modified with AlCuP alloys.A lot of dimples can be observed on the fractured surfaces of the tensile specimen.Cleavage fracture zone was reduced for the alloy,which shows ductile fracture characteristics.The wear resistance of squeeze casting on A390alloy is better than that of Metal mold casting.The size of primary silicon is further reduced by dynamic nucleation.The shedding chance of silicon particles from the Al matrix is reduced.The wear resistance of the alloy is improved.In addition,the pores、bubbles、segregation and other defects of A390alloy were reduced by mechanical stress.And the density was increased.The wear resistance of A390alloy is further improved.