Research On Strength And Toughness Of A356 Alloy With High Iron Content And Application On Wheel Hub

A356 alloy is one kind of the casting aluminum alloy,which exhibits excellent properties such as high specific strength,outstanding corrosion resistance,fast heat dissipation and high recovery rate.Therefore,it has been used widely in the automotive and aerospace industries.But when the Fe content in A356 alloy is higher,a kind of hard and brittle needle-like phase containing Fe element would form in the alloy.This needle-like phase in the alloy would seriously fragmented the aluminium base,and significantly reduced the mechanical properties of A356 alloy.In this paper,the effect of Mn and Mg elements on the microstructure and mechanical properties of the A356 alloy containing 0.19wt.%Fe element was investigated.And for the application of A356 alloy in wheel hub,the optimization of composition and heat treatment on A356 alloy with high iron was studied.The results showed that the tensile strength of the high Fe A356 alloy with optimized content was obviously higher than that of the low Fe A356.The tensile strength firstly increased and then decreased with the Mg content from 0.38wt.%to 0.44wt.%.Especially,when the Mg content was equal to 0.42wt.%,the tensile properties were best,the yield strength,tensile strength and elongation were respectively 179MPa,286MPa and 9.7%.So the alloy with 0.42wt.%Mg was used to cast the wheel hub,through the same manufacturing processes,including heat treatment,turned and coated,the mechanical properties of the wheel hub cast by the high Fe A356 alloy was better,the yield strength and tensile strength were 250MPa and 296MPa respectively,but the elongation is low,only 3.0%.To ensure the strength of the alloy and improve the toughness at the same time,the heat treatment of the A356 alloy with 0.42wt.%Mg was optimized.According to the solution hardening and age hardening curves,and combining with wheel hub coating process of finishing temperature and time,the optimization heat treatment parameters were confirmed.The results suggested that after the solution treatment at 540 ℃ for 5h,ageing treatment at 130 ℃ for 4.5h and coating treatment,the yield strength,tensile strength and elongation reached to 190MPa,261 MPa and 5.6%respectively,and the impact toughness value was 25J/cm,which indicated that the mechanical properties of the high Fe A3 56 alloy after these treatment process reached to the requirements of conventional A356 alloy.