Effects of garnet particles and chill casting conditions on properties of aluminum matrix hybrid composites

In recent years, the demand of high-performance and light-weight materials was increasing for industrial applications. The present research aims to study microstructural and mechanical properties of aluminum matrix hybrid reinforced 6-12 wt.% of garnet under the effects of materials chill casting during the manufacturing aluminum matrix composite. In this research work, metallic mold and no chills were used. In order to evaluate the quality of the chill end casting microstructure, hardness, and tensile tests were conducted on the prepared composite specimens. Aluminum matrix composites underwent the chill casting process have been examined using the optical microscope, scanning electron microscopy and X-ray diffraction. Microstructure outcomes of the casted Al-composites alloy indicated that having precipitations (Al2Si, AlCuMg2Si) and Garnet particulates hard within the Al-matrix. The results showed that the copper chill casting is the better one in terms of improving the mechanical properties because of its high volumetric heat capacity. Aluminum composite with addition of 9% Garnet composite produced via copper chill casting exhibits better mechanical properties.

Assessment of Mechanism of Pore Formation in Directionally Solidified A356 Alloy

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.

Direct Materials Deposition: Designed Macro and Microstructure

Rapid Fabrication of three-dimensional shapes of engineering materials such as H 13 tool steel and Nickel super alloys are now possible using Direct Materials Deposition (DMD) technique. H 13 tool steel is one of the difficult alloys for deposition due to residual stress accumulation from martensitic transformation. However, it is the material of choice for the die and tool industry. DMD offers Copper chill blocks and water cooling channels as the integral part of the tool. On the other hand ZrO2 was co-deposited with nickel superalloys using DMD. This process thus is amenable to produce both macro and microstructure to a designed specification. This paper briefly reviews the state of the art of DMD and describes the microstructure and mechanical properties of selected engineering alloy systems deposited by DMD.