Study On The Weldability Of 2195 Al-Li Alloy Of Tank Material For Carrier Rocket

Our research intends to make a 600 mm diameter aerospace fuel tank simulator with spray formed and smelting type 2195 Al-Li alloy,while the weldability and joint characteristics after welding of the two alloys we are not yet clear.Based on this,this paper employs a variety of welding methods to discuss the weldability of the two alloys,and to assess the performance of the joint after welding through tensile,metallographic and hardness test,verifying the weldability of S2195 F state aluminum alloy.The experimental results show that the grain coarsening and intergranular cracks caused by the second heat input are the direct reasons for the poor performance of the welded 2195 Al-Li thick plate during VPTIG welding.The grain size of the single layer welding of the weld zone is about 35 μm,while the grain size of the multilayer welding of the backing layer grows from 25 μm to 160 μm,meanwhile resulting in liquefaction micro-cracks.The strength of FSW joint is obviously improved,and the strength coefficient of the joint is 0.65.The welding process of EBW is very unstable.The joints with edge dense pores are the fracture origin.When VPPA is added to the device without shielding gas,the oxidation of the weld surface is very significant.The fracture form of the VPTIG weld of melting type 2195 welded by conventional VPTIG is intergranular fracture;While the fracture form of high energy VPTIG repair welding is intergranular or transgranular fracture;The weld structure has the comprehensive characteristics of two welding methods,when applying the FSW repair welding.The tensile strength coefficient of FSW repaired by FSW welding is about 0.6,and the strength of the joint is obviously reduced when applying the manual VPTIG repair welding.The weldability of S2195 F state is good,and the joint of VPTIG and FSW of S2195-F state Al-Li alloy were all broken by the side of the S2195 F material side,hence the joint is strengthened.The S2195-F state side of disimilar joint is strengthened due to under aging of welding,while the 2195-T8 and 2219-T87 state sides are softened due to over aging of welding.Although the heat treatment state of the material with the same composition in the welding zone is different,the hardnessvalue is basically coincided.There are two intensifying effects in the welding zone:grain boundary strengthening and precipitation strengthening,in which the second phase intensification is the most obvious,while the boundary strengthening play a small part.