異なる鋳型に鋳込んだAC4CHアルミニウム合金鋳物の疲労特性と破壊じん性

抄録

  AC4CH aluminum alloys were cast with a sand mold, a permanent mold and a permanent mold cooled by water. From each ingot, test pieces were prepared, and provided for the tensile test, the fatigue test, and the elastic-plastic fracture toughness test. The threshold stress intensity for the fatigue crack growth was independent on the cast structure and the tensile properties, and took the value of 3.0MPa·m^1/2. There was no relations between the elasto-plastic fracture toughness and the stress intensity at final fatigue failure. The both increased with the increase of the grain size of a phase and eutectic Si. The elasto-plastic fracture toughness increased with the 0.2% proof stress, the ultimate tensile strength and the elongation. The stress intensity at final failure had no relations with the tensile properties, except the elongation.