Evaluation of Microstructure and Mechanical Properties of Ti-Al2O3 Nano-Composites Fabricated by Friction Stir Processing

Ti/Al2O3 nano-composites were fabricated using friction stir processing. In order to achieve nano-composites with different volume fraction and size of reinforcements، the rotating tool was travelled on the substrates along the grooves with various widths that were filled with 20 or 80nm sized Al2O3 powders. Nano-composites with Al2O3 volume fraction of 1. 8 to 5. 7% were resulted. Optical and transmission electron microscopy showed that the most effective factor on refining matrix grain size is the inter-reinforcements distance or in other words their volume fraction and dispersion. In addition، microstructural characterization and micro hardness and mechanical testing revealed that in addition to reinforcements، reduction of matrix grain size and interactions related to reinforcements/sub-grain features such as grain boundaries and dislocations are responsible for the enhancement of mechanical properties of the fabricated nano-composites.