The Fatigue Behaviour of the Aligned Al-Al 3 Ni Eutectic Alloy

The fatigue behaviour of the unidirectionally solidified Al-Al₃Ni eutectic has been studied at room temperature, at 593 K, and at 743 K and the fracture mechanisms have been investigated by optical metallography and scanning electron microscopy. At room temperature and 593 K there is a change in the mode of fracture as between high and low stresses. At high stresses the fatigue-resistance is controlled by fibre cracking in planes of maximum shear stress, whereas at low stresses fibre buckling predominates and leads to failure because of local fibre misalignment. At 743 K the failure mode is similar at all stresses and is due to weakening resulting from fibre misalignment.