一方向凝固させたAl-Cu共晶合金の破壊様式と引張強度

概要

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To study the behavior of fracture of unidirectional solidified Al-CuAl₂ eutectic composites, the specimens with varying solidification rate, 1mm/hr～50mm/hr, were prepared by means of Bridgman method. Most of all specimens showed well-regulated lamellar eutectic structure; i.e., aluminum rich matrix and CuAl₂ lamellae were parallel to the longitudinal direction of the specimen, with few exceptions, e.g., banding structure, degenerate structure produced at the lower solidification rate. Tensile testing of these specimens revealed that the failure occured by a transverse cleavage of CuAl₂ platelets and a shear fracture of the matrix between cracks on adjacent CuAl₂ platelets. There are many cracks in the CuAl₂ lamellae near the final fracture surface, but the distribution of platelet cracks was not uniform. The tensile strength of the specimen obtained was about 24kg/mm², and this actual strength showed good agreement with the Kelly-Tyson discontinuous-fiber composite relations.