A mek diffusion bonding technique was developed to make a joint of Ti and A1, which had been regarded as almost impossible because of high activity. Fatigue crack growth rates, da/dN of the Alfri interfaces were measured experimentally at various stress ratios and compared with pure Ti and A1. The interface showed a resistance to fatigue crack propagation as good as that of aluminum alloy. The proposed universal equations on the basis of the crack closure concept made it possible to predict da/dN for various AK and R. Fatigue crack was observed to grow in the A1 side adjacent to the interface along the direction parallel to the interface. It was observed to form the intermetallic compounds in the interface region.

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