Al-based metal matrix composites reinforced with Al–Cu–Fe quasicrystalline particles: Strengthening by interfacial reaction

• Strength of composites is enhanced as the QC-to-ω phase transformation advances.
• Yield strength increases from 195 to 400 MPa with QC-to-ω interfacial reaction.
• Reducing matrix ligament size explains most of the strengthening.
• Improved interfacial bonding and nano ω phase explains divergence from model.

The interfacial reaction between the Al matrix and the Al62.5Cu25Fe12.5 quasicrystalline (QC) reinforcing particles to form the Al7Cu2Fe ω-phase has been used to further enhance the strength of the Al/QC composites. The QC-to-ω phase transformation during heating was studied by in situ X-ray diffraction using a high-energy monochromatic synchrotron beam, which permits to follow the structural evolution and to correlate it with the mechanical properties of the composites. The mechanical behavior of these transformation-strengthened composites is remarkably improved as the QC-to-ω phase transformation progresses: the yield strength increases from 195 MPa for the starting material reinforced exclusively with QC particles to 400 MPa for the material where the QC-to-ω reaction is complete. The reduction of the matrix ligament size resulting from the increased volume fraction of the reinforcing phase during the transformation can account for most of the observed improvement in strength, whereas the additional strengthening can be ascribed to the possible presence of nanosized ω-phase particles as well as to the improved interfacial bonding between matrix and particles caused by the compressive stresses arising in the matrix.