Study On Microstructure And High-low Temperature Mechanical Behavior Of Al-Cu-Mg-X Alloy Fabricated By Large Strain Rolling

The national large aircraft project has put forward higher requirements for the high temperature mechanical properties of heat-resistant aluminum alloys,and it is urgent to develop 2xxx series heat-resistant aluminum alloys in the temperature range of 150³00?.However,the service temperature of 2524 aluminum alloy is below 150?,which is difficult to meet the development needs of large aircraft projects.Therefore,the development of large-size,high-strength,high-toughness and heat-resistant aluminum alloy sheets preparation methods,which is to meet the needs of aviation manufacturing industry for high-performance heat-resistant aluminum alloy sheet has become an urgent problem to be solved,is the current scientific and engineering research focus.In order to meet this demand,in this paper,the production of aircraft skin material 2524 heat-resistant aluminum alloy as the base metal,by adding a small amount of Zr,Er and Sc alloy elements to adjust its composition,studying the effects of rolling temperature and strain rate on the formability,mechanical properties and microstructure evolution of Al-Cu-Mg-X alloy,and the uniaxial tension of Al-Cu-Mg-X alloy sheet at high temperature to study the effects of different deformation temperature and tensile strain rate process parameters on the microstructure and properties of Al-Cu-Mg-X alloy during the process of large deformation rolling.The conclusions and rules of this study are as follows:?1?There is obvious dendrite segregation in the as-cast structure of Al-Cu-Mg alloy,and the non-equilibrium eutectic structure??Al?+??Al₂Cu?+S?Al₂CuMg?is formed during solidification.The optimum homogenization process of Al-Cu-Mg alloy with different contents of Zr,Er and Sc alloy elements is 485?×10 h.?2?When the rolling strain rate is 10S^-1 and the temperature is 400?,the formability of Al-Cu-Mg alloy sheet is the best.After solid solution treatment,the coarse second phase in the microstructure of A4 alloy is basically dissolved into?-Al matrix.The effect of aging strengthening is determined by the solid solution degree of the alloy,the higher the solid solution degree which the more strengthening phases precipitate in the aging process,the better the strengthening effect.?3?By adding a small amount of Zr,Er and Sc alloy elements,the grain size of as-cast Al-Cu-Mg alloy can be refined,and a large number of dispersed Al₃?Zr,Er,Sc?particles can be precipitated after solid solution treatment.This particle can inhibit the recrystallization of the alloy and improve the strength of the alloy.The strengthening mechanisms of Al-Cu-Mg alloy are mainly fine grain strengthening,substructure strengthening and Al₃?Zr,Er,Sc?particle precipitation strengthening.?4?With the increase of Zr content,the strength of Al-Cu-Mg alloy increases after final aging treatment at 150?×4 h.When Zr contains 0.5wt%?A4?,the tensile strength,yield strength and elongation of Al-Cu-Mg alloy are 645 MPa,548 MPa and 11%,respectively.The strength of Al-Cu-Mg alloy decreases with the increase of Er content.When Er contains 0.1wt%?A7?,the tensile strength,yield strength and elongation of Al-Cu-Mg alloy are 638 MPa,542.3 MPa and 9.6%,respectively.The strength of Al-Cu-Mg alloy decreases with the increase of Sc content.When Sc contains 0.1wt%?A10?,the tensile strength,yield strength and elongation of Al-Cu-Mg alloy are 623 MPa,529.6 MPa and9.6%,respectively,and its comprehensive mechanical properties are excellent.?5?The dendrites in as-cast Al-Cu-Mg?A4,A5,A6?alloys are more obvious,and a large number of bulk precipitates are distributed along the grain boundary.After large strain rolling,the fibrous structure in Al-Cu-Mg?A4,A5,A6?alloy is more obvious.The second phase is continuously and uniformly distributed along the grain boundary,and after aging treatment,uniform and fine strengthening phases,mainly S?Al₂CuMg?,??Al₂Cu?and T(Al₂₀Cu₂Mn₃)phases,as well as Al₃Zr phase,are precipitated.When the content of Cu is2wt%?A6?,the mechanical properties of A6 alloy are good,and the tensile strength,yield strength and elongation are 507 MPa,430 MPa and 10.3%,respectively.With the increase of Cu content,the mechanical properties of the alloy show an increasing trend,and have excellent comprehensive mechanical properties.?6?In the process of high temperature tension,A4 alloy can be divided into two stages:strain hardening and stability.The flow stress decreases with the increase of temperature and increases with the increase of strain rate,and the temperature has a significant effect on the fracture characteristics of A4 alloy.With the increase of temperature,the high temperature slip characteristics of the fracture and the slippage of the interface of the matrix precipitated phase become more and more obvious.The hyperbolic sinusoidal constitutive model of A4 alloy is established.Through verification and analysis,it is concluded that the hyperbolic sinusoidal constitutive model can better describe the high temperature plastic deformation process of A4 alloy,and the constitutive relationship between rheological stress and strain rate is found.