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Fracture Behavior of Directional TiAl Lamellar Structures Ji Zhang High Temperature Materials Division, China Iron and Steel Research Institute Group No. 76 Xueyuan Nanlu, Beijing 100081, China zhaji@public3.bta.net.cn Keywords: TiAl alloy, Directional lamellar structures, Tensile test, Fracture behavior Abstract: In order to assess the influences of macro- and microstructure as well as the cast flaw on the tensile properties, the fracture behavior of a number of ambient tensile TiAl specimens containing directional lamellar microstructure have been analyzed.
This study conducts a number of ambient tensile tests of the TiAl alloy containing directional lamellar microstructure with their boundaries being parallel to the loading direction.
The tilted lamellar colonies that are fragile in the tensile process are transformed from the equiaxed a grains that precipitate during final solidification due to not yet well optimized heat radiation condition.
Acknowledgement This study was financially supported by National Basic Research Program of China (973 Program contract number 2011CB605503) sponsored by the Ministry of Science and Technology of China.

In addition, after the homogenizing annealing[3], the crystal grain formed by 7150 aluminum alloy often exhibits an equiaxed grain structure, but with large crystal grain structure.
Fund project The department of science of qinghai province’s projectItem number: ( 2013-G-Q15A-1) Author's brief introduction: Li jian (1979-),male,people in Hinghai ledu, Associate professor, master's degree Reference [1] Zhang Jiahui, Xu Guodong, Lin Wei.

Variant selection can occur in displacive transformations, in which the crystal structure changes through a shear transformation in which plates of the daughter phase are formed within a grain of the parent phase.
An increase in the uniformity of the diffraction rings for austenite can be attributable either to a decrease in grain size or to plastic deformation of the material.
Since the phase proportions and the grain size are expected to be similar for both the stress-free and loaded samples, it would seem plausible that plastic deformation in the coupon that was subjected to stress has contributed to the increase in the uniformity in the intensity of the diffraction rings.
Acknowledgements JAF would like to acknowledge funding for the Engineering and Physical Sciences Research Council (EPSRC) under grant number EP-H048294.

All of these data are then analyzed by any number of specifically developed algorithms to determine the desired material property of the specimen.
They often distribute along the grain borders.
If the indentation happens inside of the grain, e.g. region of B in figure 10, the indentation depth will be relevantly large.
While in the region of A there are many particles and borders as it is conjunction of grains.

Preface This volume contains papers presented at the International Conference "Grain boundary diffusion, stresses and segregation" - DSS-2010.
The title of the first one agreed with the conference title "Grain boundary diffusion, stresses and segregation".
As usual, in each talk as well as in conference as a whole, the experimental methods of investigations of the grain boundary diffusion and segregation played a remarkable role.
Participation of such a great number of leading scientists from all over the world was very important for us, people from MISiS, since we pay so much attention to widening of the world scientific and educational cooperation.

With the increasing number of difficult-to-machine materials coming onto the marketplace, grinding and abrasive machining processes are seeing unprecedented growth.
The chip formation is vastly different for grinding over machining, along with "tool" geometry (abrasive grains versus inserts), tool materials, tool depths of cut and cutting speeds.
The normal force required to penetrate the surface of the material, by both attritiously worn grains and loaded grains, grew to a sufficient high magnitude to cause the wheel to self-dress and become very sharp and aggressive, hence the very rough surface finish and low G Ratio. 0 5 10 15 0 100 200 300 400 500 Seconds Power - hp. 12.5% 15.0% 17.5% 20.0% 22.5% 25.0% 27.5% 30.0% 35.0% 40.0% 45.0% 50.0% Figure 2.

The particle size of crystal grain separated and granular material on average is 0.1mm to 10mm.
Screen slit width is usually similar to or a bit bigger than average grain size of treatment material.
If screen is chosen improperly, especially first-level screen, and if sieve mesh number is undersized, percent opening will be inadequate, which will lead to untimely dewatering, uneven material distribution on first-level screen and increase in pushing resistance.
Fig.3 Milled expanded metals diagram Expanded metals slit width S and spacing K are decided by such parameters as article size distribution of material separated and grain shape.

Introduction La1-xSrxCo1-yFeyO3(LSCF) oxides with high cation coordination number have very stable structure, this kind of materials is oxygen ion conductor because the mutative valence cation exist.
But the half-height-widths of diffraction lines decrease obviously, which shows the grain sizes increase and surface activity decreases with the rising of temperature.
When self-combustion occur, the maximum of flame temperature may reach 1450C,and the powder grain will partly sinter and be joined at grain boundary if the temperature is higher than 1250C, the higher of degree of slight sintering appears with the higher of self-combustion temperature.

As it can be seen from the figure, the LNO deposited at room temperature and crystallized in the furnace has bigger grains than the ones deposited at high temperature, for which the grains cannot be distinguish in the picture.
This aspect can be related with the different grain growth mechanisms due to the different manner in which the crystallized layers were obtained: after deposition in the furnace or during deposition.
Also, for the highly (100) oriented films (PL2, PL4 and PL10), only the 180º can be easily switch, but there is a high probability for the 90º domains to exist, therefore a smaller number of switchable domains are present and the Pr is lower when compared with the films with lower degree of preferential orientation (PL1 and PL3).

Some specimens for the microstructural analyses were prepared by standard metallographic techniques and etched with Keller's reagent to reveal the grain structure.
A statistical analysis of mean grain size was performed in the nugget based on light microscopy images.
In all the welds, three different regions can be individuated; the one corresponding to the material nugget fully recrystallized in which particles belonging to the two alloys are recognized (Fig. 2a); the region characterized by the alternate lamellae structure in which the induced plastic deformation is not so severe to cause complete recrystallization (Fig. 2b); and the heat affected zone in which just grain growth is observed in both the side of the two different alloys (Fig. 2c).
For a stress amplitude of 80 MPa the number of cycles to failure results to be around 2x10 6 for the AA6082, 1.1x10 7 for the AA2024 and 6.5x106 for the dissimilar welds.