| The Al-Si-Cu cast aluminum alloy has the advantages of good castability,corrosion resistance,heat treatment strengthening,etc.,has a wide range of application prospects in rail transit and other fields,and has become a candidate material for complex parts.In this paper,the self-made Al-Si-Cu cast aluminum alloy is used as the raw material to study the influence of microalloying elements and heat treatment process on the structure and properties of the cast aluminum alloy.Numerical simulation is used to study the extrusion casting technology of the aluminum alloy control arm.The work carried out in this paper and the main research results obtained are as follows:(1)The effects of Ti and Ti+Ce microalloying elements on the microstructure and properties of Al-6.5Si-5Cu-0.2Zr-0.1Sr cast aluminum alloy are studied.In the Al-6.5Si-5Cu-0.2Zr-0.1Sr alloy,the coarse silicon phase appears as short rods and needles,with a size between 10-35μm,and the alloy’s tensile strength is 218.97 MPa.After adding Ti to the alloy,the silicon phase is refined into spheres or granules with a size between 5-10μm,and the tensile strength of the alloy is increased by 60.75% to352.0MPa.When Ti+Ce is added to the alloy,the silicon phase is further refined,the size is between 1-5μm,and the tensile strength reaches the maximum 368.0MPa.At this time,the toughness of the alloy is also the best,and the elongation at break is as high as 7.50%.It can be seen from the XRD analysis that the three alloy samples have dislocation strengthening effects,and the dislocation contribution intensity of the samples containing Zr,Sr and Ti+Ce is the highest,which is 105.80 MPa.The results show that the addition of Ti and Ti+Ce has a significant effect of refining the Si phase,and the addition of Ti+Ce has a better refining effect.Therefore,the optimal composition of the alloy is Al-6.5Si-5Cu-0.2Zr-0.1Sr-0.16Ti-0.1Ce.(2)The effect of heat treatment process on the microstructure and properties of Al-6.5Si-5Cu-0.2Zr-0.1Sr-0.16Ti-0.1Ce cast aluminum alloy was studied.The results show that the hardness of the alloy is related to the aging treatment time.When the aging time increases,the hardness value first increases and then decreases,then increases and then decreases,and the first peak value is lower than the second peak value.The best aging time is 12 h,at which time the hardness reaches the maximum value of 137.3HV.Under the solution treatment of 480℃×2h+490℃×2h,the structure of the alloy is the most uniform,and the size of the silicon phase is the smallest,which is basically 5-10μm,partly at 1-5μm.The hardness is 137.3HV,the conductivity is39.6%IACS,the tensile strength and elongation are 368.0MPa and 7.50%,respectively,and the mechanical properties are the best.The dislocation contribution intensity under this solid solution process is also the highest,which is 73.01 MPa.When the solution temperature and holding time increase,the Si phase gradually grows and deteriorates the microstructure of the alloy,the tensile strength and elongation of the alloy gradually decrease,and the contribution of dislocation strengthening becomes smaller.The results show that the structure and properties of the alloy show a downward trend with the increase of the solution temperature and solution time.Therefore,for Al-6.5Si-5Cu-0.2Zr-0.1Sr-0.16Ti-0.1Ce alloy,the best solution treatment process is 480℃×2h+490℃×2h,and the best aging process is 191℃×12h.(3)The squeeze casting of the aluminum alloy control arm is simulated,and the best process parameters for squeeze casting are: pouring temperature 700℃,extrusion speed 30cm/s,and mold temperature 300℃.Under this parameter,the shrinkage porosity defect of the casting is the smallest.Simulate the filling,solidification and entrainment process of castings under the best squeeze casting parameters.The filling time is 1.6252 s.When filling,the melt is filled from bottom to top,and the overflow groove is filled at the end.The filling is stable and orderly,and there are few defects in the casting.The total solidification time of the casting is 16.8622 s,and the final solidification position is at the center of the left end of the casting.The entire exhaust process is very stable,and there is no entrainment phenomenon.In summary,this paper successfully developed a high-strength and tough cast aluminum alloy with a tensile strength of 368.0 MPa and an elongation at break of7.50%.On the basis of obtaining the best alloy composition,the best solid solution process of the alloy was explored.And using numerical simulation technology to determine the best parameters of the aluminum alloy control arm squeeze casting process. |
PDF Full Text Request