Microstructure And Properties Of Die-casting RE-ADC12 Alloy

In order to better integrate different application fields and break for the barriers of traditional aluminum alloy application market,it is urgent to prepare aluminum alloy with excellent properties.Die casting aluminum alloy can be used directly because of its good surface finish,high strength and hardness,and it doesn't need a large amount of processing in general,so it has a place in today's industrial market demand.In addition,in China,rare earth resources have unique advantages.Effective use of the physical and chemical properties of rare earth to develop die-casting rare earth aluminum alloy with excellent performance can not only expand the new use of rare earth,but also fill the gap in the new application field in the demand for high-performance die-casting aluminum alloy.In order to study the structure and mechanical properties of the die casting rare earth aluminum alloy,this paper mainly takes the die casting rare earth aluminum alloy as the research object,through adding the mixed rare earth into the ADC 12 casting aluminum alloy,and then preparing the die casting rare earth aluminum alloy with different mixed rare earth contents by die casting.The results show that the addition of(La+Yb)has a good refining effect on the eutectic Si,The morphology of eutectic silicon changes from coarse lamellar to fine fibrous.When the amount of(La+Yb)is 0.6wt%,the average area of eutectic Si are 30?m2,which are 47.4%finer than that of matrix,and the secondary dendrite wall spacing of a-Al phase is 42.7%smaller than that of matrix.Of course,the addition of(La+Yb)can improve the mechanical properties of die casting ADC 12 alloy to some extent.Compared with the collected data,it is found that the mechanical properties of the alloy are improved better when the addition amount of(La+Yb)is 0.6wt.%,and the corresponding microhardness,tensile strength and elongation are increased by 18.5%,11.3%and 12.5%,respectively.At the same time,the fracture mode of the alloy is quasi-cleavage fracture when the content of(La+Yb)is 0.6wt.%and the fracture morphology is basically consistent with the change trend of tensile properties.In addition,the effect of solution treatment on the microstructure of die casting ADC 12 alloy and die casting 0.6wt.%(La+Yb)/ADC 12 Aluminum alloy was studied,and the effect of heat treatment(solution+artificial aging)on the microhardness and tensile properties of the alloy was explored.490? is selected as the best solution temperature because the existence of surface blister will deteriorate the mechanical properties of die-casting samples at high temperature.After solution treatment at 490?/1.5h without adding rare earth,the spheroidization degree of Si phases in die casting ADC 12 alloy were improved.When 0.6wt.%(La+Yb)/ADC 12 alloy is selected for solution treatment,the solution time is the best under 1h.At this time,most of the Si phase is spherical with uniform distribution,and the corners of the Si phases are effectively passivated.After heat treatment,the mechanical properties of die-casting 0.6wt%(La+Yb)/ADC 12 alloy were improved,the microhardness reached 111.63HV,which was 3%higher than that of die-casting ADC 12 alloy after heat treatment;the tensile strength and elongation were 343MPa and 6.1 respectively,which were 7.9%and 27.1%higher than that of die-casting ADC 12 alloy after heat treatment.Moreover,the fracture mode of die-casting 0.6wt.%(La+Yb)/ADC12 alloy after heat treatment is dimple fracture,and the change trend of fracture morphology and tensile property is basically consistent.On the other hand,the addition of(La+Yb)and T6 can affect the intergranular corrosion of the alloy to some extent.In terms of the intergranular corrosion width of the alloy,the addition of 0.6wt.%of(La+Yb)and the application of subsequent heat treatment can slow down the tendency towards the width spread of intergranular corrosion.The maximum corrosion width of 0.6wt%(La+Yb)/ADC 12 alloy after heat treatment is 59.9%less than that of the matrix,and the average corrosion width is 57.8%less than that of the matrix.In addition,the weight loss rate of die casting 0.6wt%(La+Yb)/ADC 12 alloy decreased by 49.6%after heat treatment.