Structure And Mechanical Properties Of Al_(65)cu_(20)ti_(15)-based Amorphousanocrystalline Alloys Prepared By High-pressure Sintering

摘要

High strength, amorphous or partly nanocrystalline, multiphase intermetallic alloys with average composition of Al_(65)Cu_(20)Ti_(15) have been processed by mechanical alloying of the elemental powders followed by consolidation using high-pressure (8GPa) sintering either at room temperature or at 300-450℃ for 1 min. Examination of the microstructural constituents using X-ray diffraction and transmission electron microscopy shows that the alloy pressed at 400℃ is primarily amorphous, while nanocrystalline intermetallic phases, Al_2Cu, Al_4Cu_9 and Al_5CuTi_2 evolve from the amorphous matrix on pressing at 450℃. The pressing temperature of 400 ℃ 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 (1490MPa). However, absence of ductility and poor fracture toughness (3.8±0.8MPa m~(1/2)) appear as the major challenges to be met for widespread application of these alloys.