Zr基バルク金属ガラスの疲労特性評価および腐食疲労き裂発生に関する研究

抄録

Fatigue tests on Zr₅₅Cu₃₀Ni₅Al₁₀ zirconium (Zr)-based bulk metallic glass were conducted under four-point bending either in air or in distilled water environment. Bulk Metallic Glasses (BMGs) are expected to be applied for many structural applications because of remarkable properties like high strength and high corrosion resistance. However, the knowledge of the fatigue strength and on the fatigue characteristics on newly developed BMGs is still insufficient. The purpose of the present study is to grasp the fatigue characteristics and the conditions of corrosion fatigue crack initiation for Zr₅₅Cu₃₀Ni₅Al₁₀ BMG. Experimental results highlight an earlier fatigue crack initiation in distilled water than in air due to stress concentration at the corrosion pits. The aspect ratio, α, of the corrosion pits where the fatigue crack initiated is approximately 1.4 regardless the stress level. To investigate the conditions of corrosion fatigue crack initiation, artificial small defect simulating corrosion pits was introduced on specimen surface. The aspect ratio, α, of fractured surface is approximately 1.6. In addition, the fatigue crack initiated from the artificial defects all has α = 1.0 or more. It suggests that it is necessary to consider the shape of the pit to define the fatigue crack initiation condition.