Effect of chilling on soundness and ultimate tensile strength (UTS) of aluminium alloy –corundum particulate composite

An investigation has been carried out to fabricate and evaluate the strength and soundness of chilled composites consisting of aluminium matrix and corundum particles (size 20–50 μm) in the matrix. The dispersoid added ranged from 3 to 9 vol.% in steps of 3%. The resulting composites cast in moulds containing metallic and non-metallic chill blocks were tested for their strength and soundness. Results of the investigation reveal the following: (1) Strength of the composite developed is highly dependent on the location of the casting from where the test specimens are taken and also on the dispersoid content of the composite. (2) Chill thickness and chill material, however, does significantly affect the strength and soundness of the composite. (3) Soundness of the composite developed is highly dependent on the chilling rate as well as the dispersoid content. An increase in the rate of chilling and increase in the dispersoid content of the material both result in an increase in the ultimate tensile strength (UTS) of the material. The temperature gradient developed during solidification and volumetric heat capacity (VHC) of the chill used are the important parameters controlling the soundness of the composite. (4) Maximum interface temperature attained by the chill decreases with the increase in their VHC and the total heat absorbed by the chill increases with increase in VHC. (5) Thermal properties of the end chills are used to determine the magnitude of the temperature gradient developed along the length of the casting solidifying under the influence of chills.