It is well-known that the better the control of the liquid aluminium allows obtaining of better properties. One of the most important defects

that is held responsible for lower properties has been the presence of porosity. Porosity has always been associated with the amount of

dissolved hydrogen in the liquid. However, it was shown that hydrogen was not the major source but only a contributor the porosity. The

most important defect that causes porosity is the presence of bifilms. These defects are surface entrained mainly due to turbulence and

uncontrolled melt transfer. In this work, a cylindrical mould was designed (Ø30 x 300 mm) both from sand and die. Moulds were produced

both from sand and die. Water cooled copper chill was placed at the bottom of the mould in order to generate a directional solidification.

After the melt was prepared, prior to casting of the DC cast samples, reduced pressure test sample was taken to measure the melt quality

(i.e. bifilm index). The cast parts were then sectioned into regions and longitudinal and transverse areas were investigated

metallographically. Pore size, shape and distribution was measured by image analysis. The formation of porosity was evaluated by means

of bifilm content, size and distribution in A356 alloy.

In this study T6 heat treated 6063 aluminum alloys were used as substrate material. In order to form a bond between the substrate and the

main coating, all samples were coated with Ni-Cr-Al powders. 8 wt% Yttria Stabilized Zirconia powders (YSZ) were coated with plasma

spray technique. Thickness of YSZ was 150 m and bond coating was 36 m. XRD and SEM-EDS analyses were performed to characterize

the coating layers. These YSZ coated and uncoated samples were subjected to wear testing under different spindle speed, loading and

working distance. Wear test results were compared with the kinetic friction coefficients and weight loss values. Wear marks on YSZ

coated and uncoated samples were investigated by SEM analysis. By coating with plasma spray technique, the wear resistance of Al alloys

was increased without changing the friction coefficient. It was found that spindle speed had significant effect over the wear properties than

the load applied. By YSZ coating, wear properties were increased 10 times.

Al-4.5Cu alloys are widely used in aerospace industries due to their low weight and high mechanical properties. This group of aluminium alloys is known as 2xx series and exhibits the highest mechanical properties however this alloy is known to suffer from feedability and high tendency for hot tearing. Al-Si alloys (3xx) have improved fluidity and better feedability particularly by several modifications such as Ti, B or Sr. Eutectic temperature is decreased and mechanical properties can be enhanced. Yet, the strength values of this alloy group cannot reach the values of 2xx series. Therefore, in this study, the effect of Ag addition on the fluidity of Al-4.5Cu alloy has been investigated. Standard size spiral mould was used. The casting temperature was selected to be 770oC. Five castings were made and Weibull statistical approach was used to evaluate the results. In addition, coating of the die with BN was also investigated. It was found that Ag addition and BN coating of the die revealed the most reproducible, reliable and high fluidity values.