Crack initiation and short crack propagation of friction stir welded TC17 alloy joint

•TMAZ consists of needle-like α precipitates and elongated αp within β grains.•Fine β grains in SZ contribute to the highest strength in the 3rd layer.•Cracks tend to nucleate from HAGBs and {112} 〈111〉 slip deformation of β structure.•Fatigue cracks initiate from the 2nd layer of SZ below 210 MPa.•Crack growth exhibits a higher crack growth rate in HAZ than SZ.