Improving the fatigue strength of A7N01 aluminum alloy by adjusting Si content

As high-strength aluminum alloy for traction beam of high-speed rail, the fatigue strength of A7N01 aluminum alloy is particularly critical for its industrial application. In order to improve the fatigue strength of this aluminum alloy, three kinds of A7N01 aluminum alloy with different Si content were selected. The result indicates that, with the increase of Si element content, the fatigue strength is enhanced monotonously and meanwhile the dispersivity of S-N curves is largely reduced. Analyses of microstructure and the error of strength and hardness all indicate that the microstructure homogeneity of the alloy is improved when increasing the Si content, which is proved to be the main reason for the enhanced fatigue strength and reduced fatigue life dispersivity. Besides, it is found that the discontinuous distribution of the grain boundary precipitates due to the increase of Si content also contributes to the improved fatigue property.