Microstructure Formation and Micropillar Compression of Al-TiC Nanocomposite Manufactured by Solidification Nanoprocessing

The microstructure and mechanical responses of a pseudo-dispersed Al-TiC nanocomposite were thoroughly studied using micropillar compression and high-resolution transmission electron microscopy (HRTEM). The microstructure of the Al-7 vol pct TiC nanocomposite comprised the alpha-Al matrix, DO22-Al3Ti platelet and Al4C3, along with TiC domains in which similar to 30 vol pct TiC nanoparticles were loaded without sintering contact. The pseudo-dispersion of TiC nanoparticles was rationalized by the relationship between Van der Waals attraction, Brownian motion, and energy barrier. The microscale tetragonal DO22-Al3Ti compound exhibited excellent yield strength (YS) (1400 to 1667 MPa) and microplasticity (10.8 pct). Intermittent discrete strain bursts and size effects were observed in the single-crystalline Al/Al3Ti pillars. The remarkable YS (720 MPa) of the 3 mu m Al-30 vol pct TiC composite pillars was attributed to Orowan strengthening and load transfer. The crystallographic orientation relationship at the Al/TiC interface was identified to be [110] ((1) over bar(1) over bar1)(Al) parallel to [110] ((1) over bar(1) over bar1)(TiC), while the solid bonding guaranteed the effective load transfer and prevented the dislocation avalanche. Nano-twins and edge dislocations were observed in the HRTEM images of TiC NPs and [Al + TiC] mixture, which suggested that the major deformation mechanisms of the Al-30 vol pct TiC composite pillars were dislocation 'pile-up' and twins.