Investigation of the Effect of Forming Variables and Reinforcement Phase on the Microstructure and Hardness of Al7075-CNT Nanocomposite Fabricated by Semi-solid Powder Processing

In this research, semi-solid powder processing was used to fabricate Al7075-CNT nanocomposite. The effect of process variables including compression time, semi-solid temperature and the CNT percent on the sample’s hardness and microstructure was investigated. The 1%-CNT nanocomposite is observed to be superior in hardness compared to the base alloy, but the 2%-CNT sample’s hardness was between the base alloy and 1%-CNT sample. It was observed that the compression time and semi-solid temperature do not have a significant effect on the sample’s hardness. Compression for 10 minutes and forming temperature of 620 °C were selected as the suitable variables. Microstructural examination showed that in 1%-CNT alloy, the reinforcing phase is completely penetrated in the aluminum matrix and there is no CNT accumulation on the sample’s surface unlike the 2%-CNT sample. Quantitative analysis showed that a proper percentage of CNT had the greatest effect on the hardness. Increasing the temperature from 600 to 620 °C by 10% and increasing the compression time from 5 to 15 minutes by 2% increased the hardness of 1%-CNT samples compared to the base alloy.