1978 Volume 47 Issue 3 Pages 141-147
Fatigue test was performed on a base metal and weld metals of 5052-O aluminum alloy having each solidification structure of columnar crystals, feathery crystals and equixaed dendrites. Investigations have been made on the relation between the weld solidification structures and fatigue characteristics.
The fatigue strengths of the weld metals were less than the strength of the base metal. In the weld metals the strength of equixaed dendrites was the highest. In the base metal, columnar crystals and equiaxed dendrites, anisotropy of the fatigue strength was not observed. In feathery crystals, however, the anisotropy was observed. The crack propagation rates in the weld metals were less than the rate in the base metal. In the weld metals the rate was the lowest in equiaxed dendrites and the highest in columnar crystals. In the feathery crystals the rate was almost the same as that in columnar crystals when the growth direction of feathery crystals was parallel to the direction of propagation of fatigue cracks. When the growth direction of feathery crystals was normal to the direction of propagation of fatigue cracks, however, the rate decreased to that in equiaxed dendrites. Besides, it was made clear from the obser-vation of the feature of fatigue crack propagation that the cracks propagated very easily along twin planes of feathery crystals.