Abstract: The predictions from a grain cluster deformation texture model, GIA, are utilized to study
the nucleation texture of recrystallisation of aluminium alloys. In combination with a dislocation
based work hardening model, the propensity of specific grains in their granular environment for
select nucleation mechanisms is investigated. Quantitative criteria for the nucleation events can be
formulated. The results can be fed into a growth model of recrystallisation to predict
recrystallisation textures and lend themselves to through-process modelling.
Abstract: Subgrain rotation is a common mechanism of continuous dynamic recrystallization in
minerals and some metals. The mechanism involves new grain boundary formation by progressive
rotation of subgrains or subgrain boundary migration in regions with an orientation gradient. This
paper reviews the status of our current knowledge of rotation recrystallization in minerals. In
minerals a misorientation angle (θ) of 10˚ is often taken as the transition from subgrain boundary to
grain boundary but recent studies on olivine indicate a much higher transition angle between 15-25˚.
In contrast to a high transition angle, the onset of subgrain boundary mobility may occur at much
lower angles between 3-10˚. In consequence, rotation recrystallization in minerals often involves an
initial stage of subgrain rotation followed by subgrain growth once medium angle boundaries have
formed. Current models assume that all subgrain boundaries increase in misorientation with strain.
However, recent studies show that many different types of subgrain boundary develop in minerals.
The formation of new high angle grain boundaries is only likely along some types of geometrically
necessary boundary (GNB). The mineral halite (NaCl) is often quoted as the classic example of
rotation recrystallization yet recent electron backscattered diffraction (EBSD) studies show that only
limited grain sub-division occurs in NaCl polycrystals. This grain sub-division occurs on the scale
of large subgrains that divide the old grain into a few domains and not by the rotation of the smaller
equiaxed subgrains, as envisaged in current models. The small scale, equiaxed, mainly low angle
network of subgrain boundaries that develop in many minerals may be incidental boundaries, as
found in metals, or could be smaller length-scale GNBs. As minerals have high plastic anisotropy
and a limited number of slip systems GNBs may dominate over incidental subgrain boundaries
formed by trapping of statistically stored dislocations. New and extended models for rotation
recrystallization are needed that consider i) incidental subgrain boundaries as well as different types
of GNB, ii) the potential high mobility of medium angle (3-15˚) subgrain boundaries and iii) a link
between the development of subgrain misorientation and texture development.
Abstract: Humphreys’ simple construction to aid understanding of the patterns of rotational plastic
flow observed near undeformable particles in a ductile plastically sheared matrix can be generalised
to predict flow under hardness indenters in crystalline metals. The consequences for internal stress
distributions and polycrystalline plasticity are briefly indicated.
Abstract: Tensile tests have been carried out in the rolling and transverse directions of 'interstitialfree'
(IF) steel cold rolled to a strain of εh= -0.18. Tests in the transverse direction showed the
characteristic features of the orthogonal strain path change effect, with an initially increased flow
stress- compared to tests in the rolling direction- followed by a transient regime of very low strain
hardening. Tests were also carried out following recovery annealing of the prestrained sheet at
500°C and 600°C. Static recovery had a marked effect on the strain-induced anisotropy, but this
was not eliminated even when the cell structure generated by prestraining haD condensed to one
consisting of low-angle boundaries. This supports the view that the length scale, with respect to
active slip systems, between boundary obstacles is a significant factor in the orthogonal path change
Abstract: Possible effects of stress on the movement of grain boundaries and phase boundaries are considered
in terms of available driving forces and mechanisms. Examples of some of these effects are
presented from the literature and new experimental results. Stress may influence the kinetics of
transformation and also the microstructure and texture of the product material.
Abstract: Deformation of metals from medium to high strain significantly affect the deformation
structure as well as the recovery and recrystallization behaviour when deformed samples are
annealed. This behaviour is illustrated for FCC metals of medium to high stacking fault energy, with
emphasis on the behaviour of aluminium and aluminium alloys deformed by cold rolling to large
strain. The analysis encompasses hardness testing, EBSD and TEM. The deformation
microstructure is a lamellar structure of dislocation boundaries and high angle boundaries where the
percentages of the latter increases to about 60-80% at large strain. The macrotexture is a typical
rolling texture, which is composed of individual texture components present as micrometre and
submicrometre size volumes. In the lamellar structure correlations have been established between
microstructural parameters and local orientations showing for example variations in stored energy
between the texture components and large variations in the spatial distributions of the high angle
lamellar boundaries. Such local variations can affect the structural coarsening during recovery at
low temperature leading to significant structural difference on a local scale. The local variations in
the deformed structure can also significantly affect the structural changes taking place locally during
high temperature annealing thereby affecting the evolution of the structure and texture on a
Abstract: The development of deformation substructure and texture has been studied up to large
plastic strains in some simple Al base alloys by multiple forging. The experiments involve
successive forging strains on near-cube samples along 3 orthogonal axes up to cumulative strains of
3 or more (and temperatures from 20 to 400°C). The alloys include the commercial AA 3103 (Al-
1%Mn) and a laboratory Al-3%Mn-Sc-Zr alloy for the high temperature tests. Some complementary
experiments have been carried out on oriented single crystals of Al-0.3%Mn.
During 3D cross forging of fcc metals a clear texture composed of three symmetrical components
is formed; they are the 3 possible variants of the <110> <110> <100> crystal axes along the 3
forging axes. This macroscopic texture is demonstrated by X-ray pole figure analysis, EBSD
mapping and confirmed by crystal plasticity (CP) simulations. At room temperature the alloys
(particularly Al-Mn) exhibit significant grain refinement by grain fragmentation leading to "grain
sizes" of less than 103m. However, at temperatures ≥ 300°C in the stable Al-3%Mn-Sc-Zr alloy the
lattice rotations towards just 3 texture components leads to a high frequency of grain "fusions"; each
grain becomes surrounded by 3-5 neighbours of the same orientation so that long interpenetrating
chains of the texture components are formed; they are also confirmed by FEG-SEM EBSD and
spatially resolved texture simulations.
The behaviour of stable (Goss) and unstable (cube) single crystal orientations during the same
deformation processing is also investigated and shown to agree with the CP simulations.