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Abstract
The effect of prestrain and ageing on crack propagation in (001) [010] single crystals of 3¼% silicon iron has been studied. Tests performed at 77 K showed that the fracture stresses of crystals containing spark-induced microcracks rose with increasing amounts of prestrain at 298 K. Ageing of prestrained, precracked crystals increased the fracture stresses still further. Prestrain before cracking and fracture had no apparent effect on the fracture stress at 77 K. The temperature variation of the fracture stress of precracked crystals was also affected by prestrain and by ageing. Fracture surface examination revealed that slow crack growth commenced at the general yield stress on prestraining at 298 K.