International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In this study, mechanical alloying (MA) of Al-WC powder system was studied to produce aluminium composite powders having finer tungsten carbide fraction in aluminium matrix. For this purpose, elemental mixtures of 70 wt. % aluminium (Al) powder and 30 wt. % of tungsten carbide (WC) powder were mechanical alloyed for the duration of 2, 4 and 8 hrs. MA’ed powders then annealed at 300 ºC, 400ºC and 500ºC for 2 hours under inert atmosphere. Apparent densities of powders were measured in order to characterize both mechanical alloyed and annealed powders. Compressibility of the powders was determined by green density measurements after pressing.

Microstructural characterizations were conducted with X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Strain rates and crystallite sizes were measured according to fundamentals parameter approach (FPA) by applying Lorentzian function using software TOPAS 4.2.

Mixtures of 10, 20 and 30 wt. % of tungsten carbide powder and aluminum powder were ball milled for 2, 4 and 8 hrs to investigate the effect of percentages of the reinforcement and mechanical alloying time on microstructural properties of the produced composite powders. Finer particles were tried to obtain in ductile matrix. The milled powders were analyzed using X-ray diffraction (XRD).

Nano/micro particle size and distribution (PSD) technique was used to measure particle size and distribution. Scanning electron microscopy (SEM) was also performed to observe particle morphology.

Ni-Ti system is an interesting binary system having different intermetallic compounds. NiTi is the one of them having commercial importance because of its shape memory and superelastic characteristics. In this study, effect of mechanical alloying was studied against milling time to observe powder state changes and phase formations. 35Ni-65Ti, 45Ni-55Ti and 50Ni-50Ti compositions in Ni-Ti binary system were selected, It was possible to obtain different intermetallic compounds in Ni-Ti binary system by mechanical alloying of initial Ni-Ti powders. It is also observed that, particle size and distribution measurements, XRD phase analysis, density measurements and morphological evaluation of the mechanical alloyed powders can be used for the determination of optimum conditions for obtaining desired level of alloying and final product.

This study reports the structural evolution of equiatomic AlCuNiFeTi high-entropy alloy (HEA) from elemental materials to solid solution during mechanical alloying (MA), and further, to equilibrium phases during subsequent thermal annealing. It was justified experimentally that MA of Al-Cu-Ni-Fe-Ti powder mixture during 15 hours resulted in a single-phase nanocrystalline HEA with a structure of ВCC solid solution. During thermal annealing recovery and recrystallization of the BCC solid solution take place at temperatures ranging from 130 to 650 °C, and phase transformation, and grain growth of equilibrium phases occur at higher temperatures. The phase composition transforms to BCC and FCC solid solutions when the MA powder was annealed at 700 °C for 1 h. The BCC and FCC solid solution structure can be maintained even after the alloy was annealed at 1000 °C. The alloy powder was consolidated by pressure sintering at 800 °C with 5 GPa pressure for half an hour. The sintered sample exhibits 10.7±0.3 GPa in Vickers hardness.