Fracture behavior of bimetallic Al-Cu LBW joints

Abstract

Pulsed laser spot welding of copper tubing to aluminum sheet is currently used for the construction of solar thermal absorbers. The bimetallic joints should withstand high thermal stresses during the operation of the absorber. Among others, major influence on the fracture behavior of these joints comes from the intermetallic compounds, which form during the solidification of the weld metal. In this study several bimetallic Al-Cu spot welds have been produced by employing a Nd:YAG laser with a variable pulse shape. The welds have been characterized metallographically. Simple pull-up tests have been employed in order to assess the static strength of the joints. The fracture surfaces have been investigated with SEM. A correlation between intermetallic compound formation and fracture behavior is established.