Matvienko Y. Structure, stability and properties of intermetallic compounds of Al-Cu system and composites based on it

The structure of Al-Cu and Al-Cu/C powder composites with 17, 33 and 80 wt.% of copper after high-energy ball milling of Al and Cu elemental powders without and with graphite additives (5 wt.%) and thermomechanical treatments (annealing, cold pressing and solid-state sintering) as well as that of multilayered foils Al/Cu of the 60 and 30 nm period with 33 and 80 wt.% of copper, produced by electron-beam physical vapor deposition (EBPVD), before and after annealing were studied using X-ray diffraction analysis, differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), Raman spectroscopy, scanning electron microscopy (SEM). The mechanical properties and reactivity (heat released during exothermic reactions of the composites were considered. The peculiarities of phase formation in all synthesized composites after appropriate treatments were established. It is shown that the phase transformation process in the Al-Cu system occurs via the formation of a supersaturated solid solution of Al(Cu) or Cu(Al). Furthermore, fcc→bcc transformation occurs in the eutectic composites with bct-Al2Cu lower symmetry phase presence. The possibility of metastable disordered Al4Cu9 phase formation after high energy ball milling during 8 hours of powder composites Al-Cu and Al-Cu/C, and annealing of multilayered foils Al/Cu at the temperature of 150 ºC is revealed in a wide composition range. Its structure and chemical composition, the possibility of its ordering at 500 ºC and above is shown in the composite samples with 80 wt.% of copper have been specified. The positive effect of metastable disordered bcc-Al4Cu9 phase formation after appropriate treatments in all composites on the development of composites with a high level of microhardness (Young's modulus) and an acceptable plasticity coefficient is identified and confirmed. The highest level of reactivity was determined in the composites with a higher copper content of 80 wt.%. confirmed.