Search results

The microstructure of all investigated alloys was fully recrystallized and coarse-grained with a mean grain size of 15-60 m.
During annealing up to 120 minutes dislocation density decreases, the number of grain boundaries with banded contrast characteristic of high-angle boundaries increases, grain size increases to 0.12 m.
A banded contrast typical of equilibrium high-angle grain boundaries is revealed at many grain boundaries.
With the reduction in grain size, the SP temperature decreases.
At 700C the alloy with a grain size of 0.08 m displays the same superplastic properties as the same alloy with a grain size of 0.3 m.

In many cases there are deep incursions of the secondary grain into the primary grain structure behind the macro-boundary.
In the vast majority of cases, no special character was evident for grain boundaries around the periphery of the secondary grains.
The secondary grains are marked with ‘S’.
The small triangular grains appear to be separated from the secondary grain but with a very acute junction.
The strongest selectivity of the Goss orientation will occur when the pinning strength is high since this will increase the number of neighbouring grains that must cooperate.

Grain refinement and precipitation hardening are the main reasons for high strength, and toughness improvement can be attributed to grain refinement and particular microstructural characteristics of AF.
Large number of nanometer particles distribute in X80 pipeline steel, which is given in Fig.4.
Grain refinement can be achieved through repeated recryatallizaiton of austenite during hot rolling.
Sub grain and high density dislocations are characterization of acicular ferrite.
Large number of nanometer particles exist in experimental steel.

However, the prior austenite grain size reduced with increasing the cooling rate.
In fact, the microstructure is not stable and may degenerate during the weld processing, especially in the coarse grain heat affected zone (CGHAZ).
The prior austenite grain size was measured by Digital Micrograph Software.
a b c Fig. 3 Optical microstructures of testing steel formed via various cooling rates applied, (a) 0.02˚C/s, (b) 7.5˚C/s, (c) 60˚C/s A mixture of tempered martensite with different amounts of δ-ferrite was obtained in all conditions, and the prior austenite grain size at low cooling rate is extremely uniform, and display a very irregular shape, the average austenite grain size is large, large grains were also mixed with small grains.
On the other hand, martensite lath had been coarse greatly, and δ-ferrite of slender strip was observed, a large number of precipitate particles inside the δ-ferrite were also seen.

Microstructure of FeAl38 alloy after deformation e = 0.25 at temperature T = 1150/1000°C with a rate of 0.1 s-1, number of deformation cycles 4/4 (a) fine grains after deformation, (b) nuclei of recrystallization an migration of high angle boundaries.
The distribution of grain sizes a) and boundary misorientations as measured by linear intercept (b) after deformation at temperature T=1150/900°C with a rate of 0.1 s-1, number of deformation cycles 4/12.
Substructure of FeAl38 alloy after deformation e = 0.4 at temperature 1150/900°C, number of deformation cycles 4/12 a) subgrains with dislocations b) fine subgrains and nuclei of recrystallization Summary The applied methods of cumulative deformation on Max Strain simulator show possibility of intensive grain size reduction.
Suitable number of deformations (8, 16) and temperature of the process (1150°C /1000°C, 1150°C /900°C) enable to obtain substantial grain size reduction of the tested material.
Average grain diameter of d = 7.3 µm was obtained, that is 15 times the effect of grain size reduction.

Additionally, solutes impose a drag on moving grain boundaries.
Journal Title and Volume Number (to be inserted by the publisher) 3 Another purpose of intermediate annealing processes is to control grain size and texture of the final microstructure, that is at the end of all processing, with the purpose of achieving optimum formability and surface quality after forming in a customer process.
In fact, the latter is an important tool in controlling the Journal Title and Volume Number (to be inserted by the publisher) 7 degree of recrystallization during industrial processing.
The data show that at the onset of recrystallization a large number of soluble phases are precipitated, interfering with the on-going recrystallization process.
On Recrystallization and Grain Growth, Eds.

We chose GC and WA grains.
The GC grains are commonly used for processing brittle materials, because the particles have sharp edges and possess comparatively higher hardness than WA grains.
The WA grains are comparatively tough.
Fig. 2 shows the effect of the average particle diameter of the abrasive grains on the machined surface roughness by changing the number of blasting times.
Since the mixture ratio of compressed air and the abrasive grains lowers, the interference among abrasive grains decreases.

Introduction Since both strength and toughness can be improved by grain refining, the grain refinement is important to create high strength steels.
As indicated by an arrow in Fig. 3a, continuous-recrystallized (recovery and/or grain growth) grains were observed locally.
The tensile strength, TS, increased with number of turns, and that of specimens for N = 5 and 10 showed the extremely high strength of around 1900 MPa, as shown in Fig. 5a.
It is also noteworthy in the tensile property of HPT processed disks that the total elongation, EL, increased with strain from eq = 45 to eq = 91 (number of turns from N = 5 to 10).
Such yielding behavior seems to be ascribable to the difficulty of dislocation nucleation in submicron-grained structure with stable grain boundaries [14].

The surface of coatings revealed smaller grains and uniform dense with higher layers.
However, in ceramic materials a fine-grained multi-structure with a large number of interfaces often leads to increase the toughness and decrease crack propagation rate.
SEM images shows large-grained morphology for the coatings deposited at 8 layers.
During the film layer growth suppresses the formation of the large grains with voided boundaries.
The number of layers increased resulting in decrease of the friction coefficient.

The number of newly generated ultrafine grains increased with the strain; however, the average sizes were found to be independent of strain.
The grain size, `d`, was found to depend on Z parameter.
Grain boundaries that are clearly etched are only initial ferrite grain boundaries.
Along the initial ferrite grain boundaries as indicated by arrows, equiaxed grains having a size of less than 1µm surrounded by clear grain boundaries were observed.
However, equiaxed grains having a size of less than 1µm surrounded by high angle boundaries were generated along the initial ferrite grain boundaries, though small in number.