Effect of the nanopores in the Al-Cu intermetallic phase on nanoindentation instabilities at the Al/Cu interface of a magnetic pulse impact weld

This paper investigates the features of an AlxCuy intermetallic phase produced by the high strain rate collision at an Al/Cu interface during magnetic pulse impact welding. A SEM observation coupled with a EDX analysis reveals a nanoporous Al2Cu phase. A mechanical characterization using a high resolution nanoindentation shows a P-h curve with a pop-in phenomenon which is attributed to the nanoporosity of the Al2Cu phase. As the nano-porosity fraction increases from-1 % to-6 %, the hardness decreases twofold with a linear tendency. The total cumulative length of pop-ins increases with the nanopores fraction, with a linear tendency also. The critical force of pop-ins is lowered by the porosity content. The curve of highest porosity fraction exhibits the lowest values of critical force. These observations correlate the nanopores to the pop-ins. Compared to the parent metals, the Al2Cu intermetallic phase exhibits a higher hardness in between 4 and 10 GPa.