On twinning and lamellar eutectic growth

January 16, 2011

[1] Twinning Mechanism via Synchronized Activation of Partial Dislocations in Face-Centered-Cubic Materials

B Q Li et al

In situ straining in a high-resolution transmission electron microscope and molecular dynamics simulations reveal a new deformation twinning mechanism in the face-centered-cubic structure. A twin forms via the simultaneous and cooperative activation of different Shockley partial dislocations on three (111) layers. The synchronized slip produces a zero net Burgers vector; such twining relieves local stress concentration in a shear confined to adjacent atomic layers, but induces no macroscopic shape change of the surrounding crystal.

[2] Importance of secondary and ternary twinning in compressed Ti

W Tirry et al

Twin formation during uniaxial compression of high-purity α-Ti at room temperature is investigated for both quasi-static and dynamic conditions using electron backscatter diffraction techniques. The initial texture is favorable for View the MathML source twinning, yet it is observed that secondary and ternary twins occur for both strain rates, showing a higher propensity in the dynamic case. While secondary twins may explain the difference in texture change and strain hardening between the two loading conditions, the ternary twins mainly contribute to grain fractioning.

[3] Limit of steady-state lamellar eutectic growth

Wang and Trivedi

Eutectic microstructure under rapid solidification conditions becomes unstable beyond a certain velocity that places a limit on the finest spacing and the largest interface undercooling that can be achieved for a eutectic microstructure. Expressions are developed to characterize the physics that lead to the limit of eutectic growth. Activation energy for diffusion and eutectic temperature are shown to play key roles at the limit of eutectic growth, and this limit modifies the high velocity branch of the coupled growth regime.

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