Relation Between Pre Straining Before Welding , Joint Design , And Microstructure In Welding Of (7020) Aluminium Alloy


Abstaract In the utilization of aluminum alloys for structural applications , one difficulty to be overcome is the reduction of mechanical properties of welded joints as compared to the parent material, consequent upon the weaker strength of the welded metal (WM) and the distortion in the heat affected zone (HAZ) due to the welding thermal cycle . In the present investigation the tensile characteristics of joints welded plates of 7020 alloy under Arc welding at different pre strain before welding (5 ,10 , 20 ,30 %) and joint design (single and double V with angles equal to 70º,80º,90º) are investigated ,and the subsequent microstructure evolution after welding is assessed which improve the properties . This paper show that the improvement in mechanical properties (Yield and Tensile strength) carried out with 20% pre strain at a single V with angle equal to 90º compared with double V and reduced with increasing pre strain (30%) due to phase transformation of ή to the stable microstructure η (MgZn2). And changing joint design angles has little effect on mechanical properties improvement compared with joint design shape (single and double V ). Keywords: 7020 Aluminum alloy; pre strain ; Arc welding ; joint design