Search results

Severe Plastic Deformation (SDP) processes including Hydroextrusion (HE) causes the change of the mechanical properties by the introduction of a large number of defects and significant refinement of the microstructure.
Only after a certain deformation, grains become more equiaxed.
Grain size distribution was determined using the program Micrometer .
They are most frequently mentioned two characteristics which influence the corrosion resistance: chemical homogeneity and a large number of defects in the structure of the grain boundaries.
Hydrostatic Extrusion resulted in impaired grain structure.

Fine oxide particles appear to pin grain boundaries and result in inhibition of grain growth in the alloy matrix.
Table 2 Microstructural parameters of materials tested: Grain Size (D), Particle Size (d), Particle Number Density (N), Interparticle Spacing (Nd), Particle Types.
Materials Grain Size, D (μm) Particle Size, d (nm) Particle Number Density, N (m-3) Interparticle Spacing, (Nd)-0.5 (nm) Particle Types 19Cr-ODS Ferritic FCY1 3.07 9.6 5.41×1022 43.9 YCrO3, Cr2O3, Y2O3 FCY2 4.23 10.0 4.64×1022 46.4 FCY3 5.48 11.7 2.85×1022 54.8 FCY4 7.25 12.6 1.73×1022 67.7 Table 2 summarizes grain size, particle size, particle number density, and interparticle spacing for each 19Cr-ODS ferritic alloy determined by the SEM and TEM micrographs.
This is because an increase in consolidation temperature and time (1100 °C × 4 h to 1200 °C × 8 h) results in the decrease of number density and the size increase of dispersed oxide particles.
N and d refer to the particle number density and the mean particle diameter.

Grain refinement was achieved in both steels after all rolling schedules.
The initial austenite grain size, D0, and the average recrsytallised grain size, Drex were measured from quenched specimens immediately after soaking or after roughing.
Austenite Grain Size.
As expected, Drex decreases with increasing εapp due to the increased number of nucleation sites.
Li, Static recrystallized grain size of coarse-grained austenite in an API-X70 pipeline steel, Journal of Materials Engineering and Performance 22(12) (2013) 3626-3630

Titanium alloy plates have a penetration internal microstructure with a large number of ASBs.
It was indicated that the number of ASBs increased and its average width increased slightly with the increase of the velocity.
A large number of studies suggested that bifurcation phenomenon in the expansion process of ASBs was very common, and it appeared in the middle or the end of the expansion of ASBs.
It will increase the number of ASBs.
We classified grains as deformed grains, subgrains and dynamic recrystallized grains according to the value of 3°and 5.7°.

Due to changing the deformation axis, the fraction of severely deformed areas increases with increasing number of passes and very high cumulative strain becomes possible [16,17].
The number of deformation bands was rose owing to increasing a cumulative strain from 3 to 6.
Grain growth led to increasing the grain size in a fine grained area from 5.3 to 8.2 µm in the samples pre-deformed at 400 °C.
The mean grain size in a fine-grained area increased from 10.2 µm to 10.9 µm and fraction of fine recrystallized grains decreased from 54% to 32%.
Bimodal grain structure with 40 % of coarse grains and 60 % of fine grains was formed after 4 cycles.

The alloy shows typical equiaxed b grains with second phase precipitation and twin formation inside the b grains in the as-rolled condition.
Solution treatment at lower temperature led to a smaller b grain size while higher temperature solution treatment produced coarse grains with increasing precipitated phases inside the β grains.
After double solution treatment and ageing, the alloy has an increasing number of α phase particles at the grain boundaries, locally connected like a pearl necklace and a further coarsened β phase structure as shown in Fig. 1d.
For the solution treated and aged sample, thermal exposure increased the β grain size and the number of precipitates appearing within the grains.
Funkhouser, Coating for prevention of titanium combustion, NASA report number CR-165360, 1980

The magnetic behavior of this material is controlled mostly by the final average ferrite grain size.
The microstructure and mechanical properties resulting from annealing cold rolled semi-processed GNO electrical steel depend on a number of processing conditions.
As can be seen, annealing during 60 seconds causes full recrystallization and grain growth.
On the other hand, faster heating at 30 °C/s decreases the total time available for recristallization and growth of the ferrite grains and produces a smaller grain size.
As can be seen, on the average, the ferrite grains have very similar sizes (9.2 vs 10.7 µm) and there is a smaller number of particles precipitated at grain boundaries and within the grains in the former material.

This bar was numbered pass 0.
The roll passes in the wire rod block were numbered from one to eight with the odd numbered being the oval passes and the even numbered the round passes.
For the determination of grain size a minimum number of at least 200 grains and 8 data points per grain has been recommended [5], and these recommendations are followed in this study for both grain and subgrain size determination.
Results and discussion The mean size for all grains (>10°), the recrystallized grains and the subgrains in deformed grains are shown in Fig. 1a.
(b) Map of recrystallized grains growing into a deformed grain after pass 7.

Also specimens with the mean grain size of 1, 7 and 30 mm were obtained by controlling annealing of ultrafine-grained preforms produced by the isothermal multiaxial forging [6] at 480, 600, 700 and 800°С, respectively to check the effect of initial grain size on twinning.
The intensity of twinning in HCP metals is controlled by a number of factors [7].
a b Figure 4 - The influence of the initial grain size on the fraction of twinned grains in 10% cold rolled CP titanium (a) and the microstructure of titanium with the initial grain size of 1mm after rolling to 10% (b).
The investigation of the microstructure of CP titanium with different grain size rolled at room temperature to e=10% have shown that activity of twinning increased with increase in grain size reaching maximum fraction of twinned grains at grain size of 15¸30mm.
To intensify the formation of the ultrafine-grained structure due to twinning, a CP titanium with relatively low level of impurities and with grain size ³15mm should be used.

Cast alloys are designated using three digits along with a decimal designation as Xxx.x, in which first digit shows the major alloying elements and the second and third are the arbitrary numbers given to specify the alloy.
The decimal number with “0” identifies it as casting and “1” or “2” identifies as ingot structure [2].
Mark Easton et al. has derived a relation between grain size (d) and solute content , considering a growth restriction factor Q, potency and number density of nucleant particles, The term a is related to the maximum density of active TiB2 nucleant particles within the melt, while b is related to their potency [23]
Ramesh et al. has studied on the mechanical properties of multi directional cryoforged Cu-Ti Alloy and confirms that Grain size reduces to 2 µm after 3 cycles of MDF, Density of the shear bands increases and width of the shear bands decreases as the number of MDF passes increase and shows that yield, ultimate strength, Hardness increase by increasing number of passes as strain hardening [33].
[23] Mark Easton And David Stjohn “An Analysis of the Relationship between Grain Size, Solute Content, and the Potency and Number Density of Nucleant Particles” Metall.