The grain boundary geometry for optimum resistance to growth of short fatigue cracks in high strength Al-alloys

Abstract

In this paper, recent work on the effects of micro-texture on the growth behavior of short fatigue cracks in high strength aluminum alloys (such as Al-Li 8090 alloys and AA 2026 Al alloys) was first reviewed. The twist and tilt angles of crack plane deflection at a grain boundary were identified as the key factors that controlled the growth of a short fatigue crack across the grain boundary in these alloys. A large twist angle of the crack plane deflection at the grain boundary gave rise to a higher resistance to crack growth across the grain boundary, while a small twist angle represented a smaller resistance. The possible smallest twist angle of crack deflection at a boundary between a grain with a typical orientation (such as brass and goss orientations) and a randomly orientated grain was calculated and mapped in Euler space. The orientation of the neighboring grain that showed high resistance to crack growth was identified as a peak in these twist angle plots. The theoretical results were consistent with the results obtained from studies of short crack growth in AA 8090 and AA 2026 Al alloys. The results from this work paved the way to quantification of the texture effects on early growth of fatigue cracks in planar slip alloys.