Dislocation jump distances during creep of pure and doped NaCl single crystals using nuclear magnetic resonance pulse techniques

1089-7550

AIP Digital Archive

Physics

Jump distances of dislocations are determined from the spin-lattice relaxation rates in a rotating frame [1/T1ρ] using in situ nuclear magnetic resonance pulse techniques during creep of pure and doped NaCl single crystals. Effects of divalent impurity and solid solution are investigated by doping with Ca and LiCl, respectively. Compression creep tests were performed at 10–30 MPa at 473 K. Relaxation rates were evaluated from spin-echo heights following π/2, locking, and 64° pulse sequence. The amplitude of the spin echo decreased as soon as the load was applied following which it increased until the steady-state creep was reached, at which point a saturation value was observed. Mean jump distance of the mobile dislocations decreased with strain during the transient creep reaching a constant value at the onset and during the secondary creep. While the addition of 0.01 Ca has negligible influence on the jump distance, a solid solution with 0.01 LiCl resulted in about a four-fold increase. The results are compared and correlated with various microstructural parameters.

Electronic Resource