Search results

Figure 4b shows the same area observed with different tilt: in the picture on the left, several columnar grains within the rounded area can be observed, whereas in the picture on the right, there is a nanostructure with grains even smaller than 10nm.
Other encountered grains of above 1 µm size (Figs. 5c and d) also matched to a cubic lattice.
TEM images of the HVOF-NiTi coating showing: (a) oxide bands and amorphous areas; (b) columnar austenite NiTi grains; and (c) equiaxed micro-scale grains with also austenite phase.
Austenite was even identified in the columnar grains where solidification was thought to be more rapid.
Cinca also wants to acknowledge the Ministerio de Educación y Ciencia for the grant of researcher personnel with reference number AP-2004-2453.

A number of factors contributed to the high TFT achieved sintered at 1000-1100 °C.
Almost all grains seen in MS and NR pellets were equiaxed and their average grain sizes were given in Table 1.
In addition, numerous small CaO grains were formed at the boundaries between HA grains because of the decomposition of HA in the thermal etching process.
The elongated grains and CaO grains made it difficult to calculate NS pellet’s average grain size.
Instead, the aspect ratio (grain length/width) was calculated and a value of 5 ± 1 was obtained after measuring 24 randomly selected elongated grains.

Quite recently, the present authors have presented that the ultrafine-grained (UFG) Ti-64 alloy (with an average grain size of 0.4 mm) consisting of almost single a(HCP) phase exhibited an excellent property of low-temperature and high-strain-rate superplasticity [8].
It is seen that microstructure in deformed STQ specimen (in Fig. 5) is comprised of fully equiaxed grains with high angle boundary and retained acicular grains, indicating that formation of fine-equiaxed-grains is enhanced even at lower strain region around 0.47.
It is well recognized that superplastic deformation mechanism of Ti-64 alloy with an equiaxed grains (da £ 3mm) is dominated by grain boundary sliding in relation to the Gifkins Core-Mantle model [16].
Acknowledgement This research was partially supported by a Grant-in-aid from the Japan Society for the Promotion of Science (JSPS, Number 25709068).
Shin, Microstructural influence on low-temperature superplasticity of ultrafine-grained Ti–6Al–4V alloy, Mater.

Trans. 24A (1993) 1795- 1806. ] that coarse grains embedded in a fine-grained matrix can act as critical defects, significantly decreasing the plastic fracture strain at ambient temperature.
At such a temperature, the presence of β-phase and/or globular γ-grains as well as borides helps to suppress grain growth [13,[] W.J.
The resulting microstructure consists of globular βo- and/or γ-phase together with highly supersaturated α2-grains with a grain size well below 100 μm, containing few nm-fine g-lamellae.
In case of the DFL microstructure only supersaturated α2-grains, showing few fine g-lamellae, are present after air cooling.
A clear improvement of the creep strength is observed by elimination of βo-phase and equiaxed g-grains, which are situated along the lamellar γ/α2-colonies (see Fig. 2).

Material removal volume of a grain Micro-brittle fracture can be caused on the surface of ceramics when * max LP P≥ [7].
The material removed by one grain in some t becomes: 1 3 L hV C C L = ⋅ ⋅ � (4) Where L is the distance of single grain during some t.
Base on the relative motion locus of a grain Eq. (1), the movement track in WTDUVG of a single diamond grain is approximate expression: ' 2 ' 2 0 ( ) ( ) t l L ds x y dt = = +∫ ∫ � (5) Where, Zw is the material removal rate�mm 3/min �and K are coefficient.
So the number of effective abrasive particles with two-dimensional vibration grinding is: 1 1 3 3 2 1 sin(2 ) x WTDd CGd CGd w w A f v N N ft N v vπ π   ⋅  = = −      
And the effect of the acoustic cavitation of cooling emulsion and peening of detached grains contributes to material removal.

The number of thermal shock cycles was recorded.
But when the fiber content exceeds 15 wt%, porosity is relatively high owing to a large number of micro-pores and micro-cracks in ZrO2 ceramics.
Grain nucleation and growth of ZrO2 matrix can also be seen from Fig. 3.
The crystal grains of ZrO2 matrix develop well and the structure of ZrO2 matrix is compacted.
Some glassy material is formed in grain boundary, which makes the grain boundary is not obvious.

Theoretical background The physical nature of the investigation process, is based on multiple dynamic effects of a large number of fluid particles on the surface working environment of the work piece, cause plastic deformation or destruction of the elementary parts of the surface layer of the processed material, under the efforts of a single particle impact on the surface working environment of parts.
Significant influence on the roughness of the forming surface has a grain size of abrasive grains.
Sequential reduction of abrasive grain granules provides the transition from coarse sanding operations to the more subtle.
Equation describing the dependence of the surface roughness of the abrasive grain [5] , (11) Where N3 is the grain size ; m and K are coefficients, depending of treated materials .
The formation of regularization micro relief performed many contact vibrating percussion instrument- ball - rod hardener (BRH).In this case, a large number of concurrent indenters at a sufficiently high oscillation frequency shock pulses determines the samples contact surface made by hardened steel after surface grinding and vibro-impact treatment with the sample surface calibre of the same steel after finishing and polishing.The sample surfaces after vibro- impact treatment were more resistant to wear under sliding friction than after grinding.

The as-fired samples at each step of condition A are porous and the grains are united by neck-growth.
The grain sizes have the tendency to become even as the firing and milling times increase.
The particle shapes of the as-milled samples reflect the grain shapes of the as-fired samples at each step.
This is attributed to the braking of the dense and large grains.
Therefore, the relationships between the specific Fig.3 The effects of Number of firing and milling times Fig.4 The effects of Number of firing and milling times on the average particle size D50 and the specific surface on the lattice strain η of the fillers.

Fig.2.b shows the deformation induced ferrite (DIF) along the austenite grain boundaries with true strain of 0.15, DIF formed a mesh microstructure occupied most of the austenite grain boundaries, but no DIF appeared along the austenite deformation bands which mean that the value of deformation is not enough to drive the precipitation mechanism.
Fig.2.b, c, e and f shows that DIF proeutectoid along the deformation austenite grain boundaries and the austenite deformation bands or twin bands with the increase of true strain, at the same time the morphology of deformation austenite changed into island-like and prolate-like.
Fig.3.e shows a large number of short rod-like and granular cementite when the volume fraction of ferrite was over the balance value, degenerate pearlite replaced distinct lamellar cementite became the dominating morphology.
The bright parts in the microstructure were the high carbon counting strength in the line-scan photograph which mean a higher carbon concentration, so the carbon concentration strength of the inner of deformation austenite higher than ferrite, but lower than the grain boundaries.
The low-temperature deformation produce excess DIF bringing the inhomogeneity of Gibbs free energy and carbon distribution on the microstructure, so the microstructure including a large number of austenite micro-regions with various carbon content came into being.

From the metallographic structure of the defect sample it can be seen that mischcrystal exist at the sample surface and the crystalline grain around the crack is obviously larger than normal part of the sample.
Like the transition strip, after removing the oxide layer, a lot of fine cracks can be found as well and the crystalline grain around the cracks are very large.
The thermal resistance at the oscillation hook gap is higher, and it will cause poorer heat transfer, due to what bulky austenite grains are partly generated[5].
It is analyzed that the inclusion composition consists of a large number of C element and a small amount of Na, Al, Si, K, Ca elements through surface and point scanning of energy spectrum, which can be inferred that the inclusions on slab edge are the pressed-in casting powder without fully oxidization.
Under the actions of the tensile stress of heat process, hot-quenching crack is generated, so the enrichment of Cu in the grain boundary will be one cause of crack[6].