Materials and Methods
Samples and sample preparation technique
Containers of 0.5 litres of D2O water were placed in a −15°C freezer for one week. The D2O
ice was then crushed at -8 °C using a food processor. The crushed ice was sieved and a size
fraction between 1 and 1.68 mm was used for the preparation of the final samples. The ice
powder was filled into custom made cylindrical moulds with dimensions of 2.5 cm diameter
and 7 cm height. D2O water (approx. 5 ml), close to the freezing point, was added to the
mould with a syringe while constantly stirring the ice. Finally, the ice was compressed using
a piston with holes allowing excess water to escape. The excess water (1-3 ml) was removed
using a syringe. The mould was put immediately into a −15°C freezer and the sample were
removed from the mould after one to two hours and then stored in the −15°C freezer four 4
weeks.
Deformed samples were stored in a -80 °C freezer and any handling was performed at -20 °C
or colder to ensure that no annealing or recovery took place. Hence, final thin section derived
microstructures as well as final full textural data represent the final deformation stage of each
experiment.
Full texture analysis: Details
For full texture analysis three full pole figures of the indices (100), (002) and (101) were
obtained. The pole figures were measured on a regular 5° mesh by using 5° steps in the
goniometer axes  and . To improve grain statistics an additional rocking in the range of 5°
around ω axis was applied to the goniometer during measurements still keeping the resolution
of measurements within 5°.
In-situ Neutron Diffraction measurements: partial pole figures and grain size
The instrument sample table allows the placement of either a load-frame for in-situ
deformation analysis or a goniometer used for the texture analysis after deformation. The
load frame or sample orientation can be changed allowing alignment at a certain angle with
respect to the scattering vector that is defined by the incident and scattered neutron beams
(Fig. S1). The beam geometry, load frame dimensions and detector size allowed a change of
angle in the range ±39° from the direction of the applied load. In the coordinate system of a
sample it provides a cross section of the central part of pole figure, with polar angle also
ranging over ±39°, and therefore this can be considered as a partial pole figure measurement
assuming cylindrical symmetry of the crystallographic texture (Fig. S1).
For the acquisition of the partial pole figure during deformation, the platform was moving in
1° steps. At each step, the load-frame stops and the detector acquires a 2D diffraction pattern
of the diffracted neutrons during 10 s. To cover one partial pole figure scan, with a range of
±39° in 1° steps, took 35 minutes. For the medium strain rate experiments it was sufficient to
make resolution in strain scale of ~1%. For fast experiments to keep the same strain
resolution the time per cycle was reduced to 20 minutes by increasing steps size to 2°. For
representation of the partial pole figures, the points at the same ± angle from the
compression axis were averaged and additionally binned to 5° intervals. The resultant pole
figure partial cross sections with angle from 0° to° is shown as in Fig. 2.
In addition to the texture development, the partial pole figure was used to derive the mean
grain size of the sample. The principle of the approach is to look at intensity oscillation of the
measured diffraction pattern: an infinite number of grains will give perfect diffraction peaks
without any fluctuations while a small number of grains N will give large statistical
fluctuations in comparison The observed diffraction integrated intensity is a statistical
quantity proportional to the neutron beam flux and number of crystallites which are in
reflection condition i.e. comply with Bragg’s law. The number of crystallites n is a random
quantity and it is characterized statistically by the expectation of grain complying with the
Bragg’s law. Therefore, n needs to be corrected according to the developing texture. The
calculation of the influence of the developing texture is based on information in the partial
pole figure. Once this is achieved, individual grain numbers evaluated for a series of
particular angular position and hkl reflection were averaged to produce a reliable estimate of
the numbers of grains in a sample and consequently the mean grain size. Statistical analysis
showed that mean grain size estimate is accurate within 5% error. Comparison with optically
derived grain sizes of samples analysed after deformation confirm grain size estimations by
the above mentioned neutron diffraction analysis method.
Quantitative analysis of full texture through decomposition into texture components in vol%
In order to trace quantitatively the texture evolution during progressive deformation (Fig. 2F)
the texture was decomposed into two main components using the following method. The
cylindrical symmetry (C∞) of the loading process and textures developed in samples during
loading allows us to analyses preferred orientation in terms of fibre texture components. The
full texture model consisting of the random (background) component and one/two Gaussianshape components was proven to be describing orientational distributions the same as any
other texture reconstruction methods (Harmonic or WIMV). This then allowed determination
of the volume fraction of a component within 0.5% accuracy. Each Gaussian-shape
component is described by a few parameters, intensity (%), width (°) and the crystal direction
azimuthal angle (°). Since only intensity changes significantly, the information on preferred
orientation can be represented as the relative volume fraction of the two texture components
identified.