Publication
The precipitation hardened CuCrZr alloy is used in fusion machines for the heat sink of intensely cooled plasma facing components (PFC) due to its good thermal and mechanical properties. Albeit, the feedback from its application in Tore Supra (French tokamak) showed that this alloy is very sensitive to hot tearing during electron beam welding. Hot tears also known as solidification cracks occur in solidifying parts undergoing tensile stresses that are transmitted to the mushy zone by the coherent solid underneath. In order to characterize the hot tearing susceptibility of the CuCrZr alloy, welding tests based on the investigations of the Joining and Welding Research Institute (JWRI) have been performed. Electron beam fusion lines are performed on a thin rectangular plate equipped with thermocouples and firmly clamped at its extremity in the vacuum chamber. As the width of the plate decreases, conditions leading to the formation of hot tears appear in the run-in, thus defining a critical width hot tearing wise. The JWRI welding tests are then analysed by means of numerical modelling and available hot tearing criteria. To do so, missing thermophysical and thermomechanical properties are determined by associating laboratory tests and numerical analysis. The viscoplastic strain and viscoplastic strain rate undergone by the solidifying alloy are considered as hot tearing (HT) indicators. Critical values at the onset of hot tearing are determined for this particular alloy. In addition, HT initiation conditions are compared with propagation conditions using a simple numerical approach.
António João Caeiro Heitor Coelho