The Effects Of Casting-Forging Combined Formation On Microstructure And Properties Of ADC12 Aluminum Alloy

Casting can forming complex structures,but the microstructure and properties are relatively general.Forging can get good mechanical properties and high density parts,but the forming process is relatively complex,high production cost,the production cycle is relatively long,and forging parts shape was limited,it is difficult to form a part what has complex shape.While casting-forging combined formation is combined process of the casting and forging,combining the advantages of the both.Which has many realization form,the most common form is combined the die casting and forging,it is relatively few that combined the squeeze casting and forging combination,and the squeeze casting filling speed is slow,it is requiring to use casting aluminum alloy which has good fluidity,there was not using casting aluminum alloy for casting-forging combined formation before.This paper takes ADC12 Aluminum Alloy as raw materials for casting-forging combined formation process of(the indirect squeeze casting and forging)variation of microstructure and mechanical properties,and the influence of T6 heat treatment on microstructure and mechanical behavior of the squeeze casting and casting-forging combined formation.Research results show that casting-forging combined formation strengthening mechanism is grain refinement,a refinement of Al-phase and acicular eutectic phase of Al-Si particles,Al5 Fe Si alone or in sheets,or distributed in the AlSi internal eutectic with fishbone form.After T6 heat treatment,Al-Si eutectic phase and Al5 Fe Si phase were further dispersed and refined under the fusing effect.With the increase of forging temperature(forging pressure 780 MPa),the tensile strength decreased gradually and the elongation increased gradually;With the forging pressure(forging temperature 360℃)tensile strength increased gradually,when the forging temperature exceeding 780 MPa,the tensile strength reduced,the elongation rate showed an upward trend.When forging temperature were 360 ℃and and forging pressure 780 MPa,we got the most excellent comprehensive mechanical properties,what the tensile strength and elongation are 287.75 MPa and 4.4% respectively,tensile strength were increased by 19.8% compared with squeeze casting,increased by 60.75% compared with gravity casting.From the tensile fracture morphology we can found that,the fracture of cast was typical brittle fracture,squeeze casting and casting-forging combined formation are quasi cleavage fracture,while casting-forging combined formation was more shallow and small dimple,cleavage and tearing edges becomes small,the fracture unit becomes smaller,increasing the trend of ductile fracture.The tensile strength increases with the solid solution time,when the solid solution time reache to 8 h,the tensile strength is 313.6 MPa;the Vickers hardness increases with the increase of solid solution time,and reaches to 4 h,the Vickers hardness is 90.23.but when solid solution time exceeding 4 h the Vickers hardness decreased.With the increase of solution time,the dimples become smaller,the number of cleavage planes decrease and tearing edges became small,The trend of ductile fracture increases.solution time reached 10 h,it have the most maximum number of dimples.