日本金属学会誌

J. Japan Inst. Metals, Vol. 39, No. 3 (1975),
pp. 261-267

Deformation Twinning in Cu-Si Alloy Single Crystals

Shozo Yoshioka1, Yutaka Nakayama1, Taichiro Ito1 and Hiroshi Mabuchi2

1College of Engineering, University of Osaka Prefecture, Sakai
2Graduate School, University of Osaka Prefecture, Sakai

Abstract:

Cu-Si alloy single crystals having various orientations were studied with respect to their deformation twinning behavior by tensile tests in the temperature range from -196 to 300°C. The results obtained are summarized as follows.
(1) The temperature and orientation dependences of the occurrence of twinning in Cu-Si alloy single crystals are in agreement with the previously known results of fcc crystals.
(2) When the stress for twinning is reached, a macroscopic band of twin forms, accompanied by an abrupt load drop on the stress-strain curve, and thereafter the band of twin grows jerkily (so-called serration) until the twinned region fills the specimen. The abrupt load drop and serrations vary with the deformation temperature and the composition in a way which is connected with the types of formation and propagation of the band of twin.
(3) In Cu-5.0 at%Si alloy single crystals of suitable orientation deformed at -196°C, twinning occurs even though the stress-strain curves do not show serrations, and in this case the onset of twinning is characterized by a knee in the stress-strain curve.
(4) It has been observed by transmission electron microscopy that the band of twin contains many individual fine twin lamellae, and the width of these lamellae is almost less than 0.2 μ .
(5) Twinning occurs on the primary or conjugate slip plane; and it appears that twinning predominantly takes place on the plane with higher resolved shear stress.


(Received 1974/08/15)

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