Effect of Processing Layer on Fatigue Strength of Extruded AZ61 Magnesium Alloy

Fatigue property of an extruded AZ61 magnesium alloy with the processing layer introduced by machining was investigated. Rotating bending fatigue tests were carried out with the specimen with and without the processing layer. According to results of the fatigue tests, fatigue life significantly increased by introducing the processing layer to the specimen surface. Fatigue crack initiation and propagation behaviors were observed by replication technique during the fatigue test. Fatigue crack initiation life of the specimen with the processing layer was slightly longer than that of the specimen without the processing layer. Higher fatigue crack growth resistance was also observed when the fatigue crack was growing in the processing layer in the specimen with the processing layer. The longer fatigue life observed in the fatigue test in the specimen with the processing layer could be mainly due to the higher crack growth resistance. It is speculated that the fatigue strength can be controlled by change in condition of machining process. It could be effective way in industry to improved fatigue strength only by the cutting process without additional surface treatment process.