Role of the Interfaces on the Activation of Slip Systems in The PST TiAl Alloy
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Role of the Interfaces on the Activation of Slip Systems in The PST TiAl Alloy Slim Zghal*, Haruyuki Inui**, Masaharu Yamaguchi** and Alain Couret* * CEMES-CNRS,29, Rue J. Marvig, BP 4347, 31 055, Toulouse Cedex 4, France. "**Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan. ABSTRACT The operative slip systems in the so-called PST alloy are determined by transmission electron microscopy. Both post-mortem analyses and in situ observations are presented. It is shown that glide of ordinary dislocations and twinning are the most easily deformation modes activated at yield. The role of the interfaces on the activation of these operative slip systems is then examined and discussed. INTRODUCTION The lamellar microstructure is formed by a succession of y (structure L10) and (x2 (structure DO 19) parallel lamellae related by the following relationship: (11 )Y//(0001)42 and < 1 0]//,2. In the so called PST alloy, between two oC2 lamellae, pile-up of several 7 lamellae which can take six different orientation variants are often present [1,2]. These six orientation variants can be identified by considering the stacking sequence of the planes parallel to the interface and the positioning of the monoatomic row in this plane. It follows that three interface relationships can be found at the y/y interfaces: ordered domain, twin and pseudo-twin. Three deformation modes can be activated in the y phase [3-8]: glide of a< 101 ] superlattice dislocations, glide of a/2
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