Structure, thermal and mechanical properties of in situ Al-based metal matrix composite reinforced with Al2O3 and TiC submicron particles

We report herein the structure and characterization of in situ Al-based metal matrix composites (MMCs) prepared from the Al–10 wt.% TiO2 and Al–10 wt.% TiO2–1.5 wt.% C systems via hot isostatic pressing (HIP) at 1000 °C and 100 MPa. The structure, morphology and thermal behavior of HIPed samples were studied by means of the X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results indicated that fined Al2O3 particles and large intermetallic Al3Ti plates were in situ formed in the Al–10 wt.% TiO2 sample during HIPing. However, the introduction of C to the Al–TiO2 system was beneficial to eliminate large intermetallic Al3Ti plates. In this case, Al2O3 and TiC submicron particles were in situ formed in the Al–10 wt.% TiO2–1.5 wt.% C sample. Three-point-bending test showed that the strength and the strain-at-break of the HIPed Al–10 wt.% TiO2–1.5 wt.% C sample were significantly higher than those of its Al–10 wt.% TiO2 counterpart. The improvement was derived from the elimination of bulk Al3Ti intermetallic plates and from the formation of TiC submicron particles. DSC measurements and thermodynamic analyses were carried out to reveal the reaction formation mechanisms of in situ reinforcing phases. The DSC results generally correlated well with the theoretical predictions. Finally, the correlation between the structure-property relationships of in situ composites is discussed.