In this study, powder metallurgical steel samples containing 1.5% C by weight were produced by sintering in a vacuum atmosphere at 1200°C. The impact test and dry sliding wear test specimens were prepared in accordance with ISO 5754 and ASTM G-99 standards, respectively. The wear and impact toughness properties of spherical cementite in the bainitic matrix (SCBM) microstructured specimens produced with different heat treatment routes were compared with pearlite plus primary cementite, fully tempered martensitic, fully bainitic and spherical cementite microstructured specimens in ferritic matrix (SCFM). Microstructural characterisations of all specimens were performed by SEM, EBSD and XRD analyses methods. Compared to fully tempered martensitic and fully bainitic microstructured specimens with similar hardness, both the dry sliding wear and the impact toughness properties of the specimens having SCBM microstructures were improved with the increased austempering time after spheroidisation treatment.

In this study, Charpy impact test specimens were prepared by cutting Al 7075 alloy according to ASTM-E23 standards. The prepared test specimens were dissolved in a single-phase region for 1 hour at 480°C in vacuum atmosphere and artificially aged at 120°C for 24 hours after quenching. After the first step aging heat treatment applied, the specimens were artificially aged for 5-50 hours at 180°C for the second time. Microstructural characterization and fracture surface analyzes of the specimens were determined using SEM (Scanning Electron Microscope) device, crystallographic analysis of the precipitated phases were determined using XRD (X-ray diffraction) device. The increase in the amount of ƞı phase (MgZn2) with increasing double aging heat treatment time was effective in increasing the strength. After 10 hours of double aging heat treatment, the impact toughness value is improved by 300% compared to the single aged condition.

In this study, metal matrix hybrid composites obtained by adding B4C and graphene nanoplatelets (GNPs) powders as reinforcement elements to Al7075 powders were produced by powder metallurgy (P/M) method. Mixture powders prepared by supplementing Al7075 powders with different weight ratios of B4C (2-5-10%) and GNPs (0.5%) are compressed at room temperature and at different pressing pressures (600-700-800 MPa) and then at different temperatures (500-550- 600C) was sintered in vacuum atmosphere and samples were produced in accordance with ASTM G99 standard. Density and hardness analyzes were carried out depending on the changing production parameters of hybrid composites. It was determined that the pressing pressure had a direct effect on the condensation rate of the samples and the highest density value was 2.6764 g/cm3 in the Al7075+5% B4C+0.5% GNPs sample pressed under 800MPa pressure. The hardness of the samples, on the other hand, generally increased due to the increasing amount of reinforcement element, while it also increased with the increase of pressing pressure and sintering temperature.

The effects of graphene nanoplatelets added to pure Fe powders at different rates on microstructure, hardness and electrical conductivity were investigated. Prepared mixed powders were compressed at 700 MPa pressure and sintered at 1250°C. Densities of samples were measured Archimedes technique. Scanning electron microscope was used for microstructure investigations. The hardness was measured according to ASTM E384. Phase types, average crystallite size and dislocation density calculations in sintered samples were made. Electrical resistance measurements were made with the four-point probe measurement technique. Powder mixtures containing ≤5 wt-% graphene nanoplatelets were sintered into compact samples. The smallest grain size, highest dislocation density, highest hardness and electrical conductivity values were obtained in samples containing 2 wt-% of graphene nanoplatelets.