Fatigue of metallic glasses |
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Authors: | L A Davis |
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Affiliation: | (1) Materials Research Center, Allied Chemical Corporation, Morristown, New Jersey, USA |
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Abstract: | The fatigue behaviour of Ni49Fe29P14B6Si2, Ni48Fe29P14B6Al3 and Pd77.5Cu6Si16.5 metallic glasses is examined. In the finite lifetime regime the relationship between stress amplitude (
a), fracture stress (
f), mean stress (
m) and cycles to failure (N
f) is
a=A(
f– m) (2N
f)
b
, whereA andb are 16.9 and –0.40 respectively for reduced gauge section Ni49 strips (for m 140 kg mm–2) and 27.0 and –0.44 for Pd base wires. These results are unusual in thatA 1. Consequently, a sharp discontinuity exists near
a(
f–
m) –1. In a simple tensile test failure occurs at f(= y) and 2Nf=1; for peak stresses only a percent or so less than
f the sample will withstand hundreds of cycles of stress. For uniform cross-section glassy metal filaments, a fatigue limit is observed at stress ratios (
a/
f) in the vicinity of 0.07 to 0.15. The fatigue limit for reduced section specimens is a factor of 2 higher. Fatigue failure of the Ni-Fe strips may occur under partially or fully plane stress or plane strain conditions, depending on sample thickness and stress. Final failure of the Pd77.5Cu6Si16.5 wires always occurs by general yielding of the remaining section. |
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