Laser welding of high modulus, low density Al-Li alloys

Abstract

Al-Li alloys are of considerable interest in aerospace industries because the addition of Li improves the stiffness and reduces the density of aluminum. Mechanical fastening methods are currently used to join these alloys. Although such alloys are fusion weldable using MIG and TIG methods, the major problems included hot tearing, porosity, low penetration and poor joint efficiency. In this study, a 2 kW continuous wave CO2 gas transport laser was used to weld 1.6 mm thick plates of a commercially available Al-Li alloy 2090. A comparison was made with conventional arc and electron beam welding processes. Results indicated tht the joint efficiency of laser welds was greater than arc welds and comparable to that of electron beam welds. Unlike arc welds, there was no evidence of hot tearing in the laser welds. Initial surface preparation had a significant effect on the porosity and tensile strength.Al-Li alloys are of considerable interest in aerospace industries because the addition of Li improves the stiffness and reduces the density of aluminum. Mechanical fastening methods are currently used to join these alloys. Although such alloys are fusion weldable using MIG and TIG methods, the major problems included hot tearing, porosity, low penetration and poor joint efficiency. In this study, a 2 kW continuous wave CO2 gas transport laser was used to weld 1.6 mm thick plates of a commercially available Al-Li alloy 2090. A comparison was made with conventional arc and electron beam welding processes. Results indicated tht the joint efficiency of laser welds was greater than arc welds and comparable to that of electron beam welds. Unlike arc welds, there was no evidence of hot tearing in the laser welds. Initial surface preparation had a significant effect on the porosity and tensile strength.