日本金属学会誌

J. Japan Inst. Metals, Vol. 21, No. 4 (1957),
pp. 300-304

Formation of the Cleavage Cracks by Thermal Cycles in Polycrystalline Zinc

Masayuki Kawasaki and Tadashi Ichiyama


Abstract:

Observations were made on the cleavage cracks produced in polycrystalline zinc by thermal cycles between room temperature and -196°. Cleavages are apt to begin in the vicinity of the grain boundaries. The cracks cannot continue to propagate on a cleavage plane, but jump from one cleavage plane into the adjacent one after propagating for a small distance. Therefore, the cracks are composed of small cracks in a row. These small cracks are linked up by cleavages on (1010) planes. The cracks propagate across grains and grain boundaries. Thus, polycrystalline zinc may fracture by thermal cycles. The dislocation model of cleavage crack formation involving the concept of piled-up groups of dislocations is considered, and the decrease of fracture strength of polycrystalline zinc with temperature is explained by this model.


(Received 1956/11/20)

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