Structure and mechanical properties of Al65Cu20Ti15-based amorphous/nanocrystalline alloys prepared by high-pressure sintering

High strength, amorphous or partly nanocrystalline, multiphase intermetallic alloys with average composition of Al65Cu20Ti15 have been processed by mechanical alloying of the elemental powders followed by consolidation using high-pressure (8 GPa) sintering either at room temperature or at 300–450 °C for 1 min. Examination of the microstructural constituents using X-ray diffraction and transmission electron microscopy shows that the alloy pressed at 400 °C is primarily amorphous, while nanocrystalline intermetallic phases, Al2Cu, Al4Cu9 and Al5CuTi2 evolve from the amorphous matrix on pressing at 450 °C. The pressing temperature of 400 °C appears most promising, leading to products with negligible porosity, increment in the Young's modulus by about 85% with respect to that of Al alloys, as well as impressive hardness (7.9 GPa) and compressive strengths (1490 MPa). However, absence of ductility and poor fracture toughness (3.8 ± 0.8 MPa√m) appear as the major challenges to be met for widespread application of these alloys.