Effect of Ni addition on fatigue properties of bulk glassy Zr 50Cu40Al10 alloys

Abstract

We examined Wöhler curves of Zr50Cu40Al 10 and Zr50Cu30Ni10Al10 bulk glassy alloys (BGAs) using a rotating-beam fatigue test to evaluate the effect of addition Ni on fatigue strength. As a result, we found that the fatigue limit was increased from 250 MPa to 500 MPa by adding 10 at% Ni instead of Cu to a Zr50Cu40Al10 BGA. Zr 50Cu40Al10 BGAs exhibit wider fatigue-fractured region with striation-like marks than that of Zr50Cu 30Ni10Al10 BGAs. Additive Ni element limits the fatigue-fractured region to half of the whole fractured surface. We also measured dimensions of fatigue-fracture area of Zr50Cu 40Al10 and Zr50Cu30Ni 10Al10 BGAs to estimate the value of fatigue-fracture toughness. Especially, the fatigue fracture toughness decreases suddenly around 105-̃104 cycles, similar to the Wöhler curves. The significant decrease of fatigue-fracture toughness originates from embrittlement/hardening in front of the fatigue crack tip during fatigue test.