The Effect Of Heat Treatment On Microstructure And Properties Of Spray Forming 2195 Al-Li Alloy

With the development of aerospace industry,aerospace aluminum materials have attracted the attention of researchers all over the world.The weight reduction of aerospace aluminum materials is of great significance to reduce the waste of fuel resources and improve the flight distance of the aircraft.The development of aerospace materials with low density and high strength has a wide application prospect in aerospace field.The spray forming 2195 aluminum-lithium alloy can effectively reduce the segregation of the alloy,refine the grain size and improve the properties of the alloy.In this paper,optical microscope(OM),scanning electron microscope(SEM),transmission electron microscopy(TEM)and mechanical properties tests were used to study the relationship between microstructure changes and mechanical properties and corrosion resistance of spray forming 2195 aluminum-lithium alloy under different heat treatments.The following main conclusions are drawn:After the solution treatment,the second phase is dissolved,the microstructure of the alloy is improved,and the mechanical properties are improved to achieve solid solution strengthening.The solution temperature plays a decisive role in solid solution strengthening compared to other conditions.After solution treatment at 515 °C×40 min,the microstructure and mechanical properties are the best.The recrystallized grain size in the alloy is uniform,and only a small part of the undissolved secondary phase is distributed on the grain boundary.The tensile strength and yield strength of the alloy can reach 475 and 460 MPa,respectively,and the elongation is 8.4%.After solution treatment,the material reaches a single-stage peak aging at 205 °C×18h,and there are screw dislocations in the matrix.On the scre w dislocations,and some T1 phases distributed between the dislocations.They have a certain interaction with the dislocations,so that the strength of the alloy gets greatly improved and the plasticity is lowered.After the unipolar peak aging of the material,the secondary phase of the 2195 aluminum-lithium alloy supersaturated solid solution is mainly the T1 phase.Compared with the solid solution state,the T1 phases in the alloy significantly distribute on the edge of the grain boundary,and a small portion of the non-precipitation zone(PFZ)is formed around the T1 phase.With the increase of the aging time,the T1 phase grows and coarsens,the non-precipitating zone grows around T1,and the electrochemical corrosion property is greatly different.The material has the best corrosion resistance in the solid solution state,and it is superior to the monopolar peak aging than the original extruded material.T1,?',?' phases are the strengthening precipitates inspray forming 2195 aluminum-lithium,and the T1 is the major strengthening precipitate in spray forming 2195 aluminum-lithium alloy.With the increasing of T8 aging time,the number of ? ' decreases,the size of T1 grows up,and the strength of alloy decreases.The mechanical properties of alloy(7%pre-strain+205 ?×24 h)are the best,the highest tensile strength of alloy and the yield strength of alloy is 561 MPa and 558 MPa respectively with the elongation of 1.6%,and the hardness is 228 HV.