Study on small crack growth behavior of laser powder bed fused Ti6Al4V alloy

Abstract The small fatigue crack growth (FCG) behavior in Ti6Al4V alloy manufactured by selective laser melting (SLM) was experimentally investigated on an in situ fatigue testing machine. A semi‐elliptical artificial defect was introduced into the specimen to simulate the pore defects induced during additive manufacturing (AM) process. The results indicated that the fatigue life was mainly consumed in the small FCG stage. The FCG rate was significantly affected by microstructure at the early small FCG stage with great fluctuations. With the increase of crack length, the effect of microstructure decreased. Compared with long crack growth data, it was found that small crack can still grow below the threshold value of long crack, and at the same stress intensity factor (SIF) Δ K , the FCG rate of small crack was higher than that of long crack. Therefore, the small crack growth behavior should be considered in fatigue life prediction for SLM Ti6Al4V.