Dislocation wall and cell structures and long-range internal stresses in deformed metal crystals

The microstructure and solid state phase transformations which take place in aluminium alloys containing lithium have been assessed. In addition to the binary Al–Li system, the Al–Li–Cu, Al–Li–Mg, ...

Solid state phase transformations in aluminium alloys containing lithium

As a tribute to the scientific work of Professor David Brandon, this paper delineates the possibilities of utilizing in situ transmission electron microscopy to unravel dislocation-grain boundary interactions. In particular, we have focused on the deformation characteristics of Al–Mg films. To this end, in situ nanoindentation experiments have been conducted in TEM on ultrafine-grained Al and Al–Mg films with varying Mg contents. The observed propagation of dislocations is markedly different between Al and Al–Mg films, i.e. the presence of solute Mg results in solute drag, evidenced by a jerky-type dislocation motion with a mean jump distance that compares well to earlier theoretical and experimental results. It is proposed that this solute drag accounts for the difference between the load-controlled indentation responses of Al and Al–Mg alloys. In contrast to Al–Mg alloys, several yield excursions are observed during initial indentation of pure Al, which are commonly attributed to the collective motion of dislocations nucleated under the indenter. Displacement-controlled indentation does not result in a qualitative difference between Al and Al–Mg, which can be explained by the specific feedback characteristics providing a more sensitive detection of plastic instabilities and allowing the natural process of load relaxation to occur. The in situ indentation measurements confirm grain boundary motion as an important deformation mechanism in ultrafine-grained Al when it is subjected to a highly inhomogeneous stress field as produced by a Berkovich indenter. It is found that solute Mg effectively pins high-angle grain boundaries during such deformation. The mobility of low-angle boundaries is not affected by the presence of Mg.

In situ TEM nanoindentation and dislocation-grain boundary interactions: a tribute to David Brandon

Characterization of thermodynamic response by materials testing

Texture development in Al 1.8wt% Cu depending on the precipitation state—I. Rolling textures

https://pure.rug.nl/ws/files/36838230/1984ActaMetalldeHosson.pdf

Dislocation Dynamics in Al-Li Alloys. Mean Jump Distance and Activation Length of Moving Dislocations

https://pure.rug.nl/ws/files/14691914/1982ActaMetallTamler.pdf

Dislocation dynamics in aluminium and in aluminium-copper alloys: A nuclear magnetic resonance and transmission electron microscopic study

A combination of a servohydraulic tensile machine and NMR pulse spectrometer is described enabling nuclear‐spin relaxation rates to be recorded simultaneously with stress‐strain data incorporating tension as well as compression of nonmetallic as well as of metallic samples. The data of the mechanical system are as follows: Maximum load: 5000 N; minimum deformation speed: 10 μm s−1, maximum deformation speed: 3×105 μm s−1; deformation stroke: digitally controlled between 1 and 8×103 μm; bandwidth: dc to 1 kHz; resolution: 2–4 μm; temperature conditions of the sample: from 80 to 570 K. The operation and performance of the system is described by means of experiments observing nuclear‐spin relaxation rates which are induced by the movement of dislocations due to the finite deformation rate of the sample.

/pdf/dynamical-in-situ-nuclear-magnetic-resonance-tensile-34tilngywp.pdf

Dynamical in situ nuclear-magnetic-resonance tensile apparatus

Results are presented of investigations into the role of dislocation motion in deforming NaCl single crystals, using the technique of pulsed N.M.R. In particular, the spin-locking pulse sequence is used to measure T 1p, which is the spin-lattice relaxation time in the presence of a resonant r.f. magnetic field. T 1p, depends strongly on the mean free path L which is covered by the dislocations during successive jumps between obstacles in their glide plane. The mean free path is determined in crystals compressed in different directions, in which cases either the {110} or the {100} planes are primarily activated. It is shown that both the mean free path, measured as a function of strain rate and of the applied stress, and the work hardening differ remarkably for the two different primary slip planes. The magnitude of the mean free path is compared with the mean distance between dislocations in the crystal and the activation length of dislocations at obstacles, as obtained from mechanical stress relaxation experiments.

The orientation dependence of dislocation slip in NaCl single crystals

The mean free path of mobile dislocations has been measured by determining the spin–lattice relaxation rate of deforming NaCl single crystals as a function of temperature and of the concentration o

H. Tamler

Papers

Dislocation Dynamics in Al-Li Alloys. Mean Jump Distance and Activation Length of Moving Dislocations

Dislocation dynamics in aluminium and in aluminium-copper alloys: A nuclear magnetic resonance and transmission electron microscopic study

Dynamical in situ nuclear-magnetic-resonance tensile apparatus

The orientation dependence of dislocation slip in NaCl single crystals

The mean free path of mobile dislocations in doped NaCl single crystals measured by N.M.R. between room temperature and 300°C