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

Abstract

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 α-Al matrix, DO₂₂-Al₃Ti platelet and Al₄C₃, along with TiC domains in which ~ 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 μm 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 $\left[ { 1 1 0} \right] (\bar{1}\bar{1}1 )_{\text{Al}} \parallel [ 1 1 0 ] (\bar{1}\bar{1}1 )_{\text{TiC}}$, 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.