Mechanical performance of laser spot-welded joints in Al-Al/Cu solar thermal absorbers

Abstract

The mechanical performance of laser spot welded joints used in Al-Cu and Al-Al thermal absorber systems has been evaluated under different laser welding and mechanical loading conditions. In the experimental investigation, the effect of laser pulse shape and laser heat input on the spot weld strength has been examined under static and cyclic shear loading. The residual strength of spot welds after initial cyclic loading has also been evaluated. The experimental results are supported by metallographic analysis of welds and fractography of failed spot welds. It is concluded that the static and cyclic shear strength is primarily influenced by the laser heat input, which regulates the size of the generated laser spot weld section and to a lesser extent by the laser pulse shape. The influence of laser heat input parameter on the mechanical performance seems not to be as severe in the case of residual strength. This may be associated with the presence of brittle intermetallic compounds in the bimetallic Al-Cu welds which induce small scale defects during the welding process, thus further affecting mechanical performance leading to a reduction of the load bearing capacity of the spot weld.