Original paper

TEM study of mechanical twinning in experimentally deformed chalcopyrite (CuFeS2) single crystals

Couderc, Jean-Jacques; Hennig-Michaeli, Christa

European Journal of Mineralogy Volume 1 Number 2 (1989), p. 275 - 294

24 references

published: May 3, 1989
manuscript accepted: Nov 30, 1988
manuscript received: Jun 27, 1988

DOI: 10.1127/ejm/1/2/0275

BibTeX file

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Abstract : {112}(111ֿ) deformation twinning was operative besides several slip modes on {112}, (001) and {100} planes during experimental deformation of chalcopyrite single crystals at 200 °C (0.41 Tm), under 300 MPa confining pressure and at a strain rate of ~ 4-10-6 s-1. The twinning crystallography with K1= {112}, K2 = {112}, N1 = (111), N2= (HI), S = {110} and s = 0.676 specifies the twinning Burgers vector on successive {112} layers of the a-B1set as bT = 0.16 < 1/6 . Groups of sword-shaped micro-twins are inhomogeneously distributed in crystals of particular orientations. TEM observations reveal that the incoherent twin boundaries contain closely-spaced straight twinning dislocations parallel to (111) of pure screw character. The thickness of the twins does not exceed several tens of nm. Twinning as a single glide mode does not give rise to any strain hardening. The interaction between slip and twinning reduces the macroscopic shear stress for twin formation and seems to contribute to strain hardening even at small strains, in the case that early twins work as barriers for slip dislocations. Slip bands in {112} planes are blocked at crossing micro-twins. On twin boundaries, dislocations align along the intersection between slip planes and the twin boundary. Dislocations of the slip system [110] (001) can cross slip through (1ֿ12־) micro-twins via (001)T planes and (112־)T planes. The flag dissociation of a partial dislocation 1/2 [110] leads to the formation of a pair of twinning dislocations separated by a Frank partial, so that a monolayer micro-twin is nucleated. There is some TEM evidence that the reproduction of this process in successive (112) layers has formed a (112) multilayer micro-twin.


chalcopyritedeformation twinsTEMdislocations