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

Abstract

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. [doi:10.2320/jinstmet.JC201414] (Received November 12, 2014; Accepted December 22, 2014; Published March 1, 2015) Keywords: aluminum copper alloy, aluminum zinc alloy, nickel phosphorus plating, fatigue strength, aging, surface precipitate, hydrogen gas