Origin of plasticity in ultrafine lamellar Ti-Fe-(Sn) composites

Abstract

Transmission electron microscopic studies of eutectic Ti68.38Fe28.61Sn3 upon 5% and 10% plastic deformation reveal slip transfer across the β-Ti/FeTi lamellae interface. Stroh's analysis suggests that addition of Sn to Ti70.5Fe29.5 increases the cleavage stress and reduces the slip stress around a dislocation pile-up at β-Ti/FeTi interface. The presence of ultrafine lamellar FeTi contributes strengthening whereas, dislocation slip is the origin of plasticity in high strength Ti-Fe-(Sn) composites

Mechanism of lamellae deformation and phase rearrangement in ultrafine β-Ti/FeTi eutectic composites

“…Along this direction, Maity and Das has revealed that the dislocation-lamellae interaction improves the strength and the ultrafine lamellar phases contribute to strain-hardening during plastic deformation. Whereas, slip transfer across the lamellae interface improves the global plasticity in UECs, which has been also supported by the model calculations [31]. However, the effects of alloy addition and lamellar spacing on the deformation mechanism in homogeneous UEC, especially activation volume and strain rate sensitivity, have not been studied systematically.…”

“…In order to study the deformation behavior of the individual eutectic phases i.e. b-Ti and FeTi, single phase polycrystalline alloys with nominal compositions of Ti 80 Fe 20 , Ti 82 Fe 10 Sn 8 , and Ti 51.5 Fe 48.5 have been prepared according to our earlier reports [31]. These compositions have been schematically shown as dotted lines in binary TiFe alloy phase diagram, as illustrated in Fig.…”

“…Therefore, yielding has occurred in b-Ti lamellae at first upon loading and dislocations piled-up at the b-Ti/FeTi interface. On the other hand, addition of Sn reduces the shear modulus of b-Ti from 52 GPa (Ti 80 Fe 20 ) down to 38 GPa (Ti 82 Fe 10 Sn 8 ) [31]. Therefore, Sn addition possibly has changed the deformation mechanism in UECs [30].…”

“…Therefore, the dislocation density increases in both the ultrafine phases in relatively soft regions. It has been observed that sufficient number of dislocations passes across the interface at plastic strain >5% [31] and creates stepped morphology at the interface. Accumulation of significant dislocation density assists the development of sub-boundaries and hence, the flow stress rises significantly.…”

Tailoring of GaAs/GaAsSb core-shell structured nanowires for IR photodetector applications

“…Also, twins and stacking faults are observed throughout, with more stacking faults and micro-twins accumulated at the top section of nanowire. The streaky diffraction spots are likely caused by the Sb-induced strain resulting in planar defects [10]. Figure 8 shows the normalized photoluminescence (PL) spectra of nanowires at different shell growth temperatures.…”