Effect of Surface Structure and Hydrogen on the Fatigue Strength of Electroless Nickel-phosphorus Plated Al-2%Cu and Al-2%Zn Alloys

In this study, the effect of the surface structure and hydrogen on the fatigue strength of electroless Ni-P plated Al-2%. Cu and Al-2%Zn alloys was investigated. As the results, the following points were clarified. (1) Large precipitates (size) were recognized near the specimen surface of the furnace-cooled Al-Cu alloy, but these were not recognized in the furnace-cooled Al-Zn alloy. (2) Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after a furnace cooling treatment was overall reduced rather than one of the non. processed specimens. (3) Fatigue strength of the Al-Zn alloy specimen subjected to Ni-P plating after the furnace cooling treatment showed a clear increase in comparison to one of non. processed materials. (4) In both the Al-2%Cu and Al-2%Zn alloy specimens subjected to Ni-P plating after the furnace cooling treatment, a clear hydrogen desorption was recognized. On the other hand, there was only hydrogen desorption from a few of the non. processed specimens. It is considered that the poor fatigue strength of the plating materials is mainly due to the interaction between the surface precipitates and hydrogen gas.