Papers by Author: Şefika Kasman

Abstract: Thixoforming and related semi-solid processing (SSP) methods require thixotropic materials. One of the many SSP techniques is the cooling slope (CS) casting process, which is simple and has minimal equipment requirements, and which is able to produce feedstock materials for semisolid processing. When the feedstock is reheated to the semisolid temperature range, non-dendritic, spheroidal solid particles in a liquid matrix suitable for thixoforming are obtained. In this study, equipment for the CS technique was first established, and then the effects of the pouring temperature and inclined slope angle on the microstructures of A380 aluminum alloy (ISOAlSi8Cu3Fe) were studied. Optimum parameters for thixoforming experiments were selected, and it was found that the microstructure produced by the inclined plate depended on its angle and the pouring temperature.

Abstract: The effects of laser machining process parameters namely, scan speed and frequency on wear performance of AISI H13 hot work tool steel were investigated in this study. The process parameters are combined with wear process factors and the responses of wear tests were evaluated. The results showed that both friction coefficient and wear rate are affected by process parameters. The average friction coefficient and wear rate increased with an increase in frequency at each set of scan speed. Lowest scan speed and highest frequency produced higher surface roughness and rough texture form.

Abstract: The aim of this study is to investigate the effect of scan speed and frequency on surface roughness and engraving depth of AISI H13 hot work tool steel. The experimental studies were conducted by fiber laser marker machine. The relationship between the parameters is showed that the highest surface roughness and depth values were achieved at lowest scan speed (125mm/s). The depth and surface roughness of engraved geometry was decreased at increase in scan speed. It was concluded that, the surface roughness and depth can be controlled by scan speed and frequency.

Abstract: In this study, A380 aluminum alloy feedstock produced with cooling slope casting was exposed to isothermal treatment to obtain a globular microstructure which is a key feature for semisolid forming. The dendritic primary phase in the conventionally cast A380 alloy has readily transformed into a non-dendritic one in ingots cast over a cooling plate from pouring temperatures between 615, 630 and 650 °C. After the casting process, isothermal treatment was carried out at 565 °C in induction unit. Isothermal treatment yields a globular microstructure. To determine the tribological properties of this alloy, a pin-on-disc tribometer was used to carry out tribological tests under dry sliding conditions. The results showed that both cooling slope casting and isothermal treatment has an effect on tribological properties.

Abstract: Owing to its superior flow and mould-filling capability, a fully globular structure is essential for semisolid processing technologies. The present work was undertaken to identify the cooling slope casting process parameters that, upon heating to the semisolid state, gives the required globular structure for the ETIAL 160 alloy. Of the two pouring temperatures investigated, 605 °C and 615 °C, the lower pouring temperature was found to provide more globular grains surrounded by liquid phases.