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The grain refinement mechanism of the Al-5Ti-1B grain refiner was studied.
The grain refinement mechanism of the Al-5Ti-1B grain refiner was studied.
Table 1 Experimental scheme of grain refinement Experimental number Addition amount (%, mass percentage) Al-5Ti-1B Al-10Ti Al-4B TiB2 powder 1 0.2 — — — 2 — 0.1 — — 3 — — 0.05 — 4 — — — 0.0064 5 — 0.1 0.05 — 6 — 0.056 — 0.0064 Results Fig. 1 Microstructures of Al-5Ti-1B (a), Al-10Ti (b), Al-4B (c) and TiB2 powder (d) Fig.1 shows the microstructure of the Al-5Ti-1B, Al-10Ti, Al-4B master alloy and TiB2 powder.
It is well known that the microstructure of as-cast pure Al without adding any grain refiner is composed of coarse columnar grains with the average grain size of 2800 μm.
Since there are a large number of TiB2 particles in Al-5Ti-1B master alloy and each TiB2 particle is a heterogeneous nucleus of an α-Al grain, hence the Al-5Ti-1B master alloy is an efficient grain refiner of pure aluminum and aluminum alloys.

The influence of low-temperature annealing (400°C during 1 hour) on the substructure parameters and phase composition of the surface layer depending on a number of cycles of ion implantation with annealing was shown in the research.
Ion implantation is considered as a significantly studied process for a number of titanium alloys [5-9].
Ti3N is situated in the octahedral interstices of the lattice, where the number of atoms of the tetranitride is approximately equal to the number of the titanium ones [18].
The conditions are created for grain boundary sliding and rotation of grains as a result of the local increase of the dislocation density and their pinning on the segregations of mixtures of oxygen and nitrogen in the boundaries of ultra-fine grains at subsequent deformation.
This approach to the controlled management of the grain boundaries structure and properties of ultra-fine grained materials was named as “grain boundary engineering” by Professor Ruslan Valiev [23].

The thin normalized strip was composed of large columnar grains and small equiaxed grains.
Goss grains were very few.
In addition, the number of Goss nucleation in the deformed {111}<112> matrices was more than that of the {111}<110> matrices.
For the misorientation distribution of grain boundaries (Fig. 4c), both Goss grains and matrix grains showed heterogeneous distribution, but the fraction of 20~45° HE grain boundaries surrounding Goss grains was apparently higher than the matrix grains.
During the intermediate annealing, Goss grains were mainly nucleated in the shear bands within the deformed {111}<112> and {111}<110> grains, and the number of Goss nucleation in the deformed {111}<112> matrices was higher than that of the {111}<110> matrices. 2.

New grains are placed at the split grain area and their new boundaries are found.
A number of grains is assigned to the particular phase (ferrite) of the modelled metal microstructure to capture the main statistical properties of the real specimen.
The remaining grains are used for modelling of the austenite grains.
The small white adjacent grains are put together to represent bigger grains with irregular shape.
Table 1: Measured and modelled results Measured sample Mathematical model Ferrite Austenite Ferrite Austenite Number of grains 543 85 543 85 Percentage of surface [%] 48,6 8,06 48,5 8,58 Average grain surface [μm2] 4,84 5,12 4,82 5,12 Median of grain surface [μm2] 1,13 3,77 1,12 3,78 Biggest grain surface [μm2] 95 27 92 26 At the Fig. 4 b) there is the final mathematical model.

As a result of the experiments, it was determined that twist extrusion leads to more grain refinement at high temperatures with more number of passes compared to equal channel angular pressing.
Fig. 6, 7 shows the variation of hardness with temperature and number of passes in TE and ECAP process respectively.
As the temperature increases the hardness also increases with increase in number of passes in both the process.
The grains which were bigger in previous passes have become oriented in one direction and narrowed down as thick banding of the grain.
· From the microstructural studies it appears that the grain boundaries are well defined and oriented with more number of passes which leads to grain refinement from 47µm to 38µm.

The properties of ultra-fine grained materials are superior to those of corresponding conventional coarse grained materials, being significantly improved as a result of grain refinement.
The specimens were processed for a number of passes up to nine, using a die channel angle of 110°, applying the ECAP route BC.
Considering the billet rotation, different processing routes are possible: route A with no rotation of the billet between consecutive passes; route BA when the billet is rotated counter clockwise 90° on even number of passes and clockwise 90° on odd number of passes; route BC when the billet is rotated counter clockwise 90° after every pass (Fig. 1, b); and route C with the billet rotated 180° after every pass [3].
Calculated accumulated equivalent strain evolution vs. number of passes.
Butu, Mechanical behavior and microstructural development of 6063-T1 aluminum alloy processed by equal-channel angular pressing (ECAP): pass number influence, JOM, 64 (2012) 607-614

This paper examines the fabrication of ultrafine-grained materials using high-pressure torsion (HPT) where this process is attractive because it leads to exceptional grain refinement with grain sizes that often lie in the nanometer or submicrometer ranges.
Thus, Fig. 4(b) shows the presence of larger grains in the center of the sample and smaller grains at the edges.
More experiments are now needed to determine the effect of straining to higher numbers of turns.
These results confirm the gradual transition to a reasonably homogeneous hardness distribution with increasing numbers of turns.
Langdon, in: Ultrafine Grained Materials III, edited by Y.T.

Role of Σ9 Boundaries in Abnormal Grain Growth of Goss Grains in Fe-3%Si Steel Approached by Solid-state Wetting.
In the previous approaches are based on the high mobility grain boundaries shared by Goss grains with other matrix grains.
Szpunar et al. [4]have proposed that Goss grains have a large number of high-angle grain boundaries with misorientation in 20-45o range.
In this mechanism, if Goss grain has a high fraction of low energy grain boundaries with matrix grains, it has high probability to occur SSW and grow abnormally.
Goss grain boundaries have low energy relations with CSL grain boundaries.

The grain size continuously decreased with increasing the addition of grain refiner.
Table 1 Number and casting parameters of the samples Number of the sample Al-5Ti-1B (wt.%) Electromagnetic condition S-1 0 N S-2 0 Y S-3 0.02 N S-4 0.02 Y S-5 0.2 N S-6 0.2 Y S-7 2 N S-8 2 Y Note: Y indicates the LFES ingot; N indicates the reference ingot.
The grain size decreases and the grains change to mixed columnar/equiaxed grains after adding 0.02 % Al-5Ti-1B grain refiner as shown in Fig. 2(c).
When the pure Al melt has 0.2 % Al-5Ti-1B grain refiner, the grains entirely transform to equiaxed grains and the grain size decreases to approximately 0.17 mm, as shown in Fig. 2(e).
The grains become equiaxed grains completely with a grain size of 0.26 mm after adding 0.02 % Al-5Ti-1B grain refiner shown in Fig. 2(d).

Moreover, the number of passes significantly improves the particle distribution.
The mean grain size decreases from 9.5 μm to 1.95μm for a 4-pass MMC.
They could achieve ultrafine grain size.
According to the results, it reveals that there is an optimum number of passes for refining the grains and increasing the pass number does not always yield to finer grains.
Furthermore the finest grains could be achieved with 4 passes FSP.