Search results

At 8 days after the soaking, microstructure of the fg-HAp changed from small grains to dense cocoon-like ones by rapid precipitation of HAp microcrystals, while at 14 days, that of the b-HAp was porous urchin-like grains, suggesting that the fg-HAp had higher bone-bonding ability than the b-HAp.
For the spongy b-HAp calcined at 1073 K for 24h, spherical grains that were less than 1 µm in size and formed micro-pores were observed, while for the fg-HAp obtained by the partial dissolutionprecipitation method, spherical moss-like grains with 1 µm in size, which consisted of about 100 nm needle-like microcrystals, were recognized.
Based on these results, it is considered that the specified pore structure of the fg-HAp ceramics permits body fluid to permeate the parts of a living body where it is used because of the number of graded micro-pores with nano-order.
At 14 days after the soaking, microstructure of the b-HAp became porous urchin-like grains of 5-6 µm (Fig.1), while at 8 days, that of the fg-HAp already changed from small grains to dense cocoon-like ones by rapid precipitation of HAp microcrystals (Fig.2).
Summary Bioabsorbable fg-HAp ceramics having gradations in both the crystallinity and the grain size of hydroxyapatite were effectively designed using bovine bone by the partial dissolution-precipitation of the spongy b-HAp ceramics.

The condenser tubing for this study was designed by their width, thickness and number of voids, i.e., 16mmⅹ1.6mmⅹ10voids.
The microstructure of the no heat-treated 1100 Al alloy was similar to 3003 Al alloy, while heat-treated sample showed the very large grain size due to grain growth after recrystallization.
The grain size just exhibited trend of increase with increasing with brazing time.
The large grain size has a profound effect on mechanical properties which have close relationship to resistance of pressure.
By the comparison between the mechanical properties and microstructure, the decrease in yield strength for the 1100 Al alloy was resulted from the large grain size due to recrystallization and subsequent grain growth as shown in Fig. 8.

The solid α-Al grains were still attached to each other, and grain separation was incomplete.
Fig.3 (a, c) shows that coarse grains break down into smaller grains while larger grains appear around them during initial passes.
Upon observing two passes through route A, the microstructure appears to comprise longitudinal grains, with some grains exhibiting more elongation and grain boundaries tending to about 45°.
When higher levels of stress are applied via pass A, the grain width is reduced, and strain bands are formed within the grains, leading to the refinement of the grains within the elongated shape.
Corrosion resistance of ultra fine-grained Ti.

The number and size of small pores were decreased with increasing sintering temperature but the full density could not be attained in the range of the present PLS condition.
The smaller grain size could be obtained from SPS compared to conventional PLS.
The average grain sizes were increased as increasing the sintering temperature.
Relationship between average grain size and sintering temperature was shown in Fig. 3 (a).
Shen, S.Osamu, Microstructural characteristics of large-scale ultrafine-grained copper.

If the internal stress was pressure, then the peak would move to the high wave number domain while if the internal stress was the tension, the peak would shift to the low wave number domain.
The characteristic peak of Sample 1# would shift to the high wave number domain while pressure existed in the film.
The size of crystalline grains was small and homogeneous.
The nucleation density of the diamond crystalline grains was low.
When the methane concentration was too low, the number of carbon-bearing groups in the atmosphere was not sufficient and the nucleation density of the diamond crystalline grains was low.

Li Yuntao et al. [5] studied the influence of strip feeding ratio on structure, the results show that equiaxed crystal ratio and equiaxed grain size is effected by the strip feeding ratio: slab equiaxed grain rate increased from 49.3% to 75.3%, increased by 52.7% and the average equiaxed grain size decreased 55.4% when strip feeding ratio increased from 0 to 3%.
Take the cross section of high times tested, where the specimen number 6442 means feeding steel strip and number 6443 means not feeding steel strip.
Tab.2 High times test results Sample number Surface microstructure 1/4 grain size grade (grade) 1/4 organization Heart organization 6442 F+P+W (Level 1) 8.9 F+P（27%）+W（Level1.5） Existence of segregation，organization：P+F+little B+W（Level 2.5） 6443 F+P+W (Level 1) 8.1 F+P（29%）+W（Level1.5） Serious segregation，organization：F+P+very little B+W（Level 2.5） Notes: (1) F- ferrite, P- pearlite, B- bainite, W- widmanstatten structure (2)Evaluated by GB/T13298-1991 "The metal microstructure test method", GB/T13299-1991 "Steel-Determination of microstructure", GB/T6394-2002 "metal mean grain size determination method" standard.
The melt grain nucleation and growth kinetics and thermodynamics conditions changed because the strip feeding changed the distribution of temperature field of molten steel and reduced the superheat of molten steel and casting section temperature gradient, which makes the columnar grain growth inhibited and the proportion of equiaxed grains increased [9].
From table 2, it can be found, casting billet grain degree at 1/4 increase after feeding the strip.

Equal channel angular pressing (ECAP) is widely studied for its potential to produce ultra-fine grained (UFG) structure in TiNi shape memory alloys (SMA).
In the present work, route Bc was used where the sample is rotated in the consecutive direction by 90o, which can attain the optimum superplastic ductility because of the most obtained equiaxed grains generation with high angle grain boundaries compared to other routes [26-29].
Results and discussion Effect of Pass Number on Homogeneity Distribution.
So it is predicted that Ci and SSD values will decrease by increasing pass number.
Fig. 4b shows the effect of pass number and plane section on SSD.

The wall of the Mg cell packing was made of much finer grains.
Introduction As the lightest structural metal, magnesium and its alloys have attracted a large number of industrial sectors for their high specific strength, machinability and cast ability [1-2].
In the as-received specimens, the structure is composed by equiaxed grains with an average grain size of about 12.7 μm.
After BE deformation, the grain size is significantly refined.
The grain size was significantly refined after BE.

The results show that MgO-MgAl2O4 composite refractory has quite excellent hydration resistance because of periclase grains with exsolved spinel phase.
MgO-spinel based refractories have a large number of applications as an alternative component of chrome containing refractory.
Though the dominant phase of samples is periclase, it can be observed that some spinel crystals with particle size of 1-5 mm have gathered on the surface of MgO grains or in the intergranular spaces between MgO grains.
There are tiny spinel crystals with perfect octahedral structure embedding on the surface of MgO grains with larger size by in situ reaction (Fig. 5(d)).
Spinel crystals with particle size of 1-5 mm on the surface of MgO grains or in the intergranular spaces between MgO grains can enhance significantly hydration resistance of magnesia.

In a polycrystal this supposition makes sense if the grains are relatively uniform before deformation.
Certain regions of the microstructure could generate a larger number of nuclei.
The number of nuclei per unit of area, NA, is equal to 1/841.
Simulations were performed for increasing number of jumps.
In real 3D recrystallization the value of NV, the number of grains per unit of volume is often estimated from the microstructural path itself or from the final grain size using simplifying geometrical assumptions.