Papers by Author: D. Božić

Abstract: Prealloyed copper powder containing 2.5wt. %Al was processed in a planetary ball mill to evaluate matrix hardening due to formation of Al2O3 particles in situ by internal oxidation. After milling, the powders were heat treated in hydrogen in order to reduce copper oxide formed on particle surfaces during milling. The compacts were made by hot pressing. The examinations show that the compacts possess a good combination of high strength and high electrical conductivities. After 5h of milling the microhardness of the prealloyed compact was 3 to 4 times higher than that of the as-received electrolytic copper compacted under the same conditions, while the conductivity was 68% IACS. Also, it was found that the prealloyed compacts preserved much of the hardness after exposure to high temperature in inert atmospheres.

Abstract: The compressive characteristics and fracture behavior of CW67 aluminum alloy and of a composite based on CW67 alloy were studied under unaxial compressive loading in the temperature range 25-400°C, at a constant strain rate of 1 - 3 10 4 . 2 s × . The yield strength values of the composite were higher than those of the monolithic alloy at all temperatures. The ultimate strength values of the composite were lower at room temperature, but higher at elevated temperatures when compared with those of the monolithic alloy. The composite exhibited lower ductility than the monolithic alloy in the entire temperature range. High concentration of SiC particles in the structure of CW67 composite affected its compressive properties. At higher temperatures, it behaved like a typical precipitation hardened alloy, in other words, with temperature increase the main influence on the mechanical properties occurred in its matrix. When temperature rises, the fracture process changes from particle cracking and particle agglomerate decohesion (at room temperature) to particle matrix debonding (at high temperature).

Abstract: The structural and compression mechanical properties of Ti3Al-based intermetallics produced by powder metallurgy techniques have been studied. The as-milled powders were compacted by hot pressing to non-porous homogenous compacts. Prior to compression tests, all compacts were homogenized by a solution treatment at 1050°C (a+β region) for 1h, followed by water quenching. The compression tests were performed from room temperature to 500°C in vacuum at a strain rate of 1 3 10 4 . 2 − − × s . Detailed microstructural characterization was evaluated by scanning electron microscopy (SEM), followed by energy dispersive spectroscopy (EDS) and X-ray diffraction analysis.