Search results

Despite the large number of studies that are being conducted to advance the friction stir processing (FSP) technology, the effects of FSP on various mechanical and microstructural properties are still in need for further investigations.
Several researchers reported the effectiveness of FSP in producing an ultrafine grain structure [3-7].
The obtained average hardness values are displayed in Fig. 3(d); confirming the effect of lateral conduction in increasing the imposed temperature and consequently increasing the grain size due to grain growth.
Finer grain size can be achieved when the maximum induced temperature is reduced.
Khraisheh: Ultrafine Grained Material III TMS, 2004

Simplified description of grain-scaled stresses in the case of <110> fibre texture Previously, a simplified model has been proposed for grain-scaled stresses in cold drawn steel wires having a strong <110> fiber texture [3].
A full-constraint condition of the grain is assumed.
The actual grain stress tensor σσσσg is eventually obtained as follows.
(2) Here the Taylor factor of the grain is defined as Μg = Γg/D.
On the one hand, there are a number of factors that should be taken into account in order to improve the model accuracy: particular shape of deformed grains and respectively changing constraint conditions, predominance of next neighbors in the grain inetraction, the substructure development in the grain interior, etc.

Preparation and Characterization of α-Fe2O3 Nanometer particles of different appearance Qiao-ling Li 1*, Hong-xia Jing 1, Li-li Cui 1 , Yun Ye 2, Ya-kun Wang 3 1 Department of Chemistry, North University of China, Taiyuan 030051, China 2 Department of materials, North University of China, Taiyuan 030051, China 3Beijing new technology population institute, Beijing 100089, China 1*Qiaolingl@163.com, 1 jhx820215@126.com, 2 yeyun200@nuc.edu.cn, 3 wyk98@163.com Keywords: microwave radiation, high temperature sintering, α- Fe2O3 nanometer grains, round, cube, rod-like Abstract.
This article uses the method of microwave radiation combined with high temperature sintering to prepare dispersive and symmetrical α-Fe2O3 nanometer grains for the first time, and this method not only may reduce the reactive cycle, but also may enhance the concentration of reactive initial solution of FeCl3.
At the same time, in the process of experiment we found that if we put different crystal promotion agents in reaction solution at different calcining heat and calcining time, we can obtain round, cubic or rod-like α-Fe2O3 nanometer grains separately.
Among them, Fig.3 tallies with 251402 standard atlases whose number is JCPD, so it proved that the proof sample isα-Fe2O3; We may see that the characteristic absorption peak of the sample from Fig.3 in 563cm-1 and 476cm -1 tallies basically with characteristic absorption peak of α-Fe2O3 which is reported in literature 5 in 580.538cm-1 and 485cm -1, so it proved that the sample obtained is α-Fe2O3.
crystal promotion agents A (mol ratio) B（min） C（℃） appearance grain diameter (nm) 1 tartaric acid 200 120 400 round 20 2 citric acid 200 60 600 cubic 80 3 Sodium dihydrogen phosphate 100 60 500 clavate 30 Acknowledgements This work was funded by National Natural Science Foundtion of China (No. 20571066), and Returned Overseas Chinese Scholars, State Education Ministry (No. 2003406).

Research on the Mechanical Properties for Medical Stainless Steel Ming Wen, Wei Li and Xiaoming Cao School of Material Science and Engineering Hebei University of Technology, Tianjin, China E-mail: gd-wen@gadvanize.com.cn, shmily_lw@126.com, gd-sam@gadvanize.com.cn Keywords: Austenitic stainless steel; Grains; Crew; Torque; Torsion angle Abstract.
The original scan 400× 00Cr18Ni14Mo3 original austenite, from Fig.1 and Fig.2 we can see a large number of slip belt within the grain and black white spots, the initial suspect that these spots may be carbides, due to the presence of these spots on the hardness of the screw, plastic , has an impact toughness.
Carried out a number of experiments, we found that the bar is heated to 950 ° heat 1h water, torque and angle can meet well.
D. 950 ℃ solution and water cooling Fig.5. 950 ℃ solution and water cooling scan 200 Fig.6. 950 ℃ solution and water cooling scan 400× Compared with the original sample, can be seen within the austenite grains slip bands disappeared completely, grain boundary is clear and grain grew up in different degrees.

The final grain size decreases with hot rolling finishing temperatures above 1040°C in spite of increasing hot band grain size, deteriorating the core loss results.
The final grain size decreases with finishing temperatures above 1000°C and hot band grain size over 200µm.
The Goss orientation is generated mainly in the sites inside shear bands [4,5,6] and the number of shear bands increases with the square rooted prior grain size [7] (hot band grain size).
Fig.4: Final grain size (FGS) and Goss volume fraction as a function of hot band grain size (HBGS).
W1.5 reduces when the final grain size increases independently if to the larger grain sizes correspond worse texture.

Introduction Results of numerous investigations show that a decrease in the grain size to the grain size range of nanocrystalline materials leads to increases by a factor of 2 to 7 in the hardness and yield strength of materials against those of coarse-grained analogs [1, 2 and other works].
No dislocations were detected in the volume of grains.
However, in the indicated temperature range, individual anomalously grew grains, the number of which is insignificant against the predominant number of disperse grains, were detected.
Only after annealing at 1873 К, the grain size of the deposited chromium ranged from 450 to 500 µm, which corresponds to the grain size in the recrystallized chromium (Fig. 2 c).
The thermally activated detachment of grain boundaries from inclusions fixing them occurs only after annealing at 1573 К and is accompanied by intensive grain growth.

Austenite grain refining enhances recovery and recrystallization rates, and decreases the size of recrystallized grains.
[10]: t )l/nl/n(x 2211 +⋅ =ρ [m -2] (8) where: x - the fraction of invisible dislocations with a Burgers vectors a/2<111> for the A1 lattice, l )2(1 - the total length of the horizontal (vertical) lattice lines, n )2(1 - the number of intersections of the horizontal (vertical) lattice lines with dislocations, and t - the thickness of the foil under investigation.
The recrystallized grains are characterized by a deformed grain boundary line, which indicates an extensive cumulated deformation in the specimens.
Deformation parameters Grain average area Grain elongation coefficient Dimensionless shape coefficient Specimen No.
An increase in strain above the value corresponding to the maximum yield stress on the flow curve induces the occurrence of dynamically recrystallized grains in the alloy structure; initially, on grain boundaries and later on inside the grains.

Secondly sample was burnished by metallographic sand paper after from number 1 to number 5, follow-on used polishing compound polishing, Finally samples were corroded by 5% of nitric acid alcohol.
A white zonal between layer allying zone and heat-affected zone is showed in Fig.2.2(a), it is seen that a number of fine needle-like crystal grain embedded in the heat affected zone.
Besides, there are more equiaxed grain and lesser columnar grain dispersive distribution in alloying layer.Why should this phenomenon take place?
There are generally four factors accounting for it. firstly, CeO2 segregates in grain boundary prioritily through Diffusion Mechanism, Because of its segregation purificate the impurity elements's segregation in grain boundary and grain boundary, then grain boundary is strengthened.The ability of resisting deformation is reinforced thereupon.
Secondly, CeO2 can reduce activity of carbon and make they can not precipitate into crystal defect and reduce the number of interstitial atoms of pindislocations.

Attempts have been made by a number of investigators to deposit molybdenum from aqueous solution.
If grain is larger than the critical size, hardness increases with decreasing grain size followed well-known Hall-Petch relationship.
For a smaller grain than the critical size, the hardness decreases with decreasing grain size.
This is known as grain size softening.
Conclusion Crack-free electrodeposits have fine and uniform grains with the average grain size of 7 nm.

Due to the possible grain growth at a higher solution temperature and fewer constituent particles within the grain (Fig. 3d), the as-quenched ZK60-Cu alloy exhibited a slightly lower hardness as opposed to ZK60 alloy.
After the solution treatment, a large proportion of particles remained at the grain boundary and interior of the ZK60 alloy.
However, only the big cuboid phase of MgZnCu could be observed at the grain boundary of the solutionized ZK60-Cu alloy.
Based on the Hall-Petch relationship, the yield strength depends much on the average grain size.
As seen from Fig. 3, the yield strengths of the two alloys are close due to the similar grain size.