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THE EFFECT OF GRAIN SIZE ON FATIGUE CRACK GROWTH IN AN ALUMINIUM MAGNESIUM ALLOY
Author(s) -
Turnbull A.,
De Los Rios E. R.
Publication year - 1995
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1995.tb00861.x
Subject(s) - materials science , grain size , microstructure , metallurgy , grain boundary strengthening , fractography , alloy , paris' law , aluminium , aluminium alloy , magnesium alloy , slip (aerodynamics) , crack closure , grain boundary , composite material , fracture mechanics , physics , thermodynamics
Fully reversed uniaxial fatigue tests were performed on aluminium magnesium alloy Al 5754 with four different grain sizes in order that the effect of grain size on fatigue crack growth could be examined. Surface cracks were monitored by a plastic replication technique. Fatigue strength was shown to improve with a decrease in grain size. The endurance stress is a function of the inverse square root of the grain size and is described empiricdty by a Hall‐Petch type relation. The effect of grain size on fatigue crack growth is most significant when the crack length is of the order of the microstructure. Fluctuations in the growth rate of microstructurally short cracks are most marked in a fine grained microstructure and may be related to the need to transfer slip to adjacent grains. Crack path deviation is greatest in the coarsest grained microstructure and SEM fractography reveals a more pronounced crack surface roughness in the coarser grained alloy than in the finer grained alloy.