| Al-Si series alloy is one of the first-choice materials for making engine pistons.At present,The research on Al-Si alloys through alloying and heat treatment methods mainly focuses on the use of traditional T6 heat treatment processes to study the effect of alloying on the intermetallic compounds in the alloy,while the effect on the ?-Al matrix is less researched.In addition,the existence of complex and diverse second phases in the alloy complicates the study of a single factor on Al-Si piston alloys.Therefore,this paper takes the ?-Al matrix in the Mahler piston alloy as the research object,prepares the alloy Al-1 Si-1Cu-0.5Mg close to the ?-Al matrix composition,And use Pandat phase diagram and DSC curve to design alloy T6 heat treatment process.Basid on this,adding Sc,Zr,Ti trace elements,and comparing different heat treatment systems,To study the effect of adding Sc,Zr,and Ti on the microstructure,tensile properties and high temperature creep behavior of Al-1Si-1Cu-0.5Mg alloy.The main conclusions are as follows:(1)The addition of trace elements Sc,Zr,and Ti will all have an impact on the grain size of the alloy.The synergistic addition of Sc,Zr,and Ti has a greater effect on the refinement of the structure than that of the separate addition.The synergistic addition of Sc,Zr,and Ti has the strongest refinement effect,and the average grain size is 113?m,which is reduced by 139?m compared with not adding Sc,Zr,and Ti alloys.(2)The hardness of the alloys with Sc,Zr and Ti alone and in combination in the as-cast state?solid solution state?and aging state are all higher than that of the base alloy.The hardness of the alloy added with Sc,Zr,and Ti is the highest,and the hardness reaches 148HV in the aging state,which is 69HV higher than that of the as-cast base alloy.At the same time,the alloy with Sc,Zr,and Ti synergistically added has the highest strength,and the room temperature tensile strength has been increased from 313MPa to 365MPa.without adding Sc,Zr,and Ti,The elongation has been increased from 1.55%to 5.1%;The high temperature tensile strength has been enhanced from 77.5MPa to 105MPa,The elongation has been enhanced from 1.9%to 8.6%.(3)After the alloys with composite addition of Sc,Zr,and Ti undergo high-temperature short-return re-aging process and high-temperature heat exposure,The tensile strength is reduced and the ability to resist deformation is weakened.but the plasticity of the alloy is enhanced,the ability to resist deformation is weakened,and it shows good impact toughness.The high temperature elongation under the re-aging process has been increased from 8.6%in the T6 state to 34.7%.As the heat exposure temperature increases,the tensile strength of the alloy has been raised from 33.7MPa to 44MPa,and the elongation also has been raised from 30.5%at 350? to 34.7%.(4)The addition of trace elements Sc,Zr,and Ti refines the grains to varying degrees and promotes the sliding of the grain boundaries.the precipitated particles of Al3Ti,A13(Sc1-xZrx),Al3(Sc1-xTix)and other particles in the alloy play a role of strengthening the second phase.However,the strengthening of the precipitation formed by the addition of alloying elements against the movement of intragranular dislocations is far less than the deformation caused by grain boundary slip after grain refinement.Therefore,the Al-1Si-1Cu-0.5Mg alloy is added with Sc,The creep behavior of the alloy after Zr and Ti elements is more likely to occur.After the alloys with elements of Sc,Zr,and Ti are subjected to the high-temperature short-return re-aging process and the high-temperature long-term thermal exposure treatment,the alloy creep process does not include the steady-state phase,and directly enters the acceleration stage from the deceleration stage. |
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