Research On SPF/DB Forming Technology Of 2B06 Aluminum Alloy Double-layer Structure

2B06 aluminum alloy is a new aviation aluminum alloy with good plasticity and toughness,which is based on the original 2A06 aluminum alloy and through strict control of the constituent elements.High temperature properties of 2B06 aluminum alloy are studied,including the thermal properties and the high temperature superplastic properties.According to the test results,the test process parameters of SPF/DB of 2B06aluminum alloy are formulated.The influence of surface roughness or smoothness,diffusion connection pressure and temperature on the process of DB for 2B06 aluminum alloy are investigated.The ideal forming air pressure is obtained by means of finite element simulation,and the time-pressure curve of superplastic forming is corrected.Finally,the quality of double-layer structure of 2B06 aluminum alloy are prepared by SPF/DB combination process.According to the thermal parameters such as thermal expansion coefficient,melting point,specific heat capacity and thermal conductivity of 2B06 alloy are measured.It is concluded that the melting point of 2B06 aluminum alloy is 609?,and the change of microstructure occurs in the temperature range of 450?⁵00?.The strain rate is 0.003s^-1,and the stretching temperature is 450?,which is the optimum superplastic forming temperature of 2B06 aluminum alloy.When this temperature is exceeded,secondary recrystallization occurs,which reduces the plasticity of 2B06aluminum alloy.The strain rate sensitivity index m value and K of 2B06 aluminum alloy under this condition are 0.2426 and 103.68MPa respectively.According to the combination results of the 2B06 aluminum alloy diffusion joint,the joint interface has a certain roughness to facilitate the diffusion connection.The pressure of 10MPa will cause severe deformation of the aluminum plate after diffusion bonding,and the connection pressure of 5MPa is better.Combined with the shear test and hardness test results,530?is the most suitable temperature for diffusion connection of 2B06 aluminum alloy.The shear strength of the diffused joints at this temperature can reach 83.57MPa.And there is no obvious connection defect on the structure,the grain size is similar to before.The high temperature stress-strain curve of the obtained 2B06 aluminum alloy was input into the finite element software.According to the simulation results,it was found that the air pressure of 3MPa was used for forming.The time taken under this condition was 1454s,and the thinning rate of the maximum thinning position of the double-layered structural member was also only 21.5%,and the stress concentration was 2.32MPa.The double layer structure is formed by SPF/DB combination process,and the connection quality and superplastic forming are analyzed.Experimental analysis of microstructure and mechanical properties of the diffusion joints of structural parts.It was found that the joint parts of the 2B06 aluminum alloy double-layer structural parts were well bonded on the microstructure,and there was no obvious diffusion joint defect,and the shear strength reached 79MPa.The maximum thickness reduction of the superplastic forming zone can be controlled within 20%.