The behavior of cracking in Mo3Al–Mo3Al8 two-phase intermetallics with lamellar structures

The behavior of cracking in Mo–Al intermetallics with two different interlamellar spacings is investigated by micro Vickers tests at room temperature. The experimental results show the coarse lamellar structure can suppress crack nucleation even under a high load of 9.8 N, whereas the fine one starts being cracked under a low load of 2.94 N. It contradicts to the general observation that toughness of alloys is better with finer grains. The experimental observations are discussed in terms of a fracture mechanics model including dislocation emission at the crack tip. The present model shows that stress concentration at crack tip tends to increase with decreasing interlamellar spacing. The experimental results are qualitatively explained by the present model.