Fracture mechanism of dispersion strengthened Al-Al4C3 materials

Dispersion strengthened Al-Al4C3 materials prepared by mechanical alloying posses good high-temperature properties at low specific weight. Their structure is heterogeneous and consists of fine grained matrix and Al4C3 particles created by chemical reaction between Al and C. The particles are incoherent, different in size. The failure mechanism was analyzed by "in situ tensile test in SEM" for Al-Al4C3 composites with 8 vol.% of Al4C3 Strain rate 6.6 10(-4) s-(1) was applied by direct loading of the thinned test piece in the scanning electron microscope in vacuum at 20 degrees C. The crack creation, coalescence, and propagation ill the test piece was analyzed. The first cracks were shown to create by failure of large Al4C3 particles in the process of loading. Further load increase caused further crack propagation by particle cracking, and matrix-particle interphase boundary decohesion. Cracks propagated also in the direction of load trough the concentration of smaller particles grouped in bands. The fracture ended by tearing the ligaments between the bands. Failure mechanism model has been introduced.