Fabrication of Al matrix in situ composites via self-propagating synthesis

TLDR: In this article, a self-propagating high temperature synthesis (SHS) was used to process 30 vol.% TiC, TiB2 and TiC+TiB2 ceramic reinforcements, followed by high pressure consolidation to full density.

Abstract: Al matrix composite materials with 30 vol.% TiC, TiB2 and TiC + TiB2 ceramic reinforcements were processed in situ via self-propagating high temperature synthesis (SHS) followed by high pressure consolidation to full density. Non-steady-state oscillatory motion of the combustion wave was observed during the SHS processing, resulting in a typical layered structure of the reaction products. The microstructure and phase composition of the materials obtained were studied using X-ray diffraction, optical microscopy and scanning (SEM) and transmission (TEM) electron microscopy. Very-fine-scale ceramic particles ranging from tens of nanometers up to 1–2 μm were obtained in the Al matrix. Microstructural analysis of the reaction products showed that the TiB2/Al and (TiB2 + TiC)/Al composites contained the Al3Ti phase, indicating that full conversion of Ti had not been achieved. In the TiC/Al composite a certain amount of Al4C3 was detected. High room and elevated temperature mechanical properties (yield stress, microhardness) were obtained in the high-pressure-consolidated SHS-processed TiC/Al and TiB2/Al composites, comparable with the best rapidly solidified Al-base alloys. These high properties were attributed to the high density of the nanoscale ceramic particles and matrix grain refinement.