The Study of Thermal Stability of Mechanically Alloyed Al-5 wt.% TiO2 Composites with Cu and Stearic Acid Additives

In this work, we studied the effect of thermal exposure on the microstructure and mechanical properties of an Al-5 wt.% TiO2 composite material with additions of 5 wt.% Cu and 2 wt.% stearic acid as a process control agent (PCA), obtained by mechanical alloying. The composite was processed in a ball mill for 10 h. Composite granules were consolidated by hot pressing at 400 °C. SEM, XRD, and DSC analyses were used to study the microstructure, phase composition, and thermal behavior, respectively. Studies showed that the hot pressing of the material with copper addition leads to the precipitation of Al2Cu particles from the supersaturated solid solution and a decrease in the microhardness to 233 HV in comparison with the as-milled state (291 HV). In the material with a PCA additive, on the other hand, the microhardness increases from 162 to 187 HV due to the formation of aluminum carbide nanoparticles. In both cases, no reduction reaction products were found. At the same time, the Al-5TiO2-2PCA material after hot pressing shows a more stable grain structure than the Al-5TiO2-5Cu material. In addition, the compressive strength at 300 °C of the former material is 1.7 times higher than that of the latter one.