Papers by Keyword: Cooling Slope Casting

Abstract: Earlier work has shown that Al-5.7Si-2Cu-0.3Mg aluminium alloy is suitable for thixoforming process. Here, the dry sliding wear behaviour of the alloy, in the as-cast and thixoformed conditions were investigated. The cooling slope technique was used to produce the alloy with globular microstructure for the thixoforming process. Both the thixoformed and cast samples were subjected to T6 heat treatments prior to the wear tests. The tests were carried out using a pin-on-disc tribometer, against a hardened M2 tool steel disc of 62 HRC at different loads, under dry sliding conditions at fixed sliding speed and sliding distance of 1 m.s^–1 and 5 km respectively. The microstructural response, worn surfaces were thoroughly and carefully examined using various methods such as scanning electron microscopy, energy dispersive spectroscopy, and differential scanning calorimetry. The density of the heat treated thixoformed alloys showed significant increase in the hardness property, among others, due to its reduced porosity. Their wear test results also observed that the weight loss of materials increase with an increase in the input load and the sliding distance for all samples. However, the as-cast alloy displayed higher wear rate compared with the thixoformed alloys. In general, the wear mechanisms showed a mixture of abrasive, oxidative and delamination wear (mild wear) at low applied loads and mainly an adhesive (severe wear) at high applied loads.

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: 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: A356/Al2O3 metal matrix composites produced by means of conventional stirring and cooling slope casting have been investigated and their microstructures were compared. The microstructure of conventional stirring cast samples are fully dendritic in contrast to equiaxed morphology of the cooling slope cast samples. The image analysis was carried out to characterize the effective volume percent of Al2O3 particles in the ingot, and the shape factor and the size of α-Al crystals. The cooling slope casting produces higher effective volume percent, having microstructures with smaller α-Al crystal size and a greater shape factor than the conventional stirring.

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.

Abstract: Vibrating the slope during cooling slope casting of a metallic alloy has shown helpful for causing the microstructure more spherical and thinner in a previous research by the present authors. This paper gives results from a direct observation of the SSM microstructure formation during cooling slope casting of an NH4Cl-H2O alloy with vibrating the slope. It is found that the vibration exerted to the slope can break down the solidification shell formed at the surface of the slope through rapid chilling and produce effectively fine globular grains in the microstructures. The main factors affecting the fine grain formation include the chilling extent, frequency and amplitude of the vibration of the slope, and the superheat of the alloy melt, respectively. The higher vibration frequency and amplitude, the lower superheat of the alloy melt, and the lower chilling temperature will help the formation of finer globular grains.