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Commercially available magnesium alloys such as Mg-AlZn and Mg-Al-Mn alloys generally show relatively poor mechanical properties at elevated temperature because of its microstructure, which is characterized by the magnesium matrix and Mg17Al12 structure at the grain boundaries [1,2].
Mg17Al12 intermetallic compound formed at the grain boundaries has low melting temperature at around 710 K and is brittle.
With the addition of Sb (Fig. 2(c)) or Sr (Fig. 2(d)), microstructural changes can be clearly observed: (1) morphology of the Mg2Si phase has modified and refined from coarse Chinese script shape to polygonal shape; (2) the average grain size of α-Mg matrix also refined (36 to 31μm on average).
Fig. 1 X-ray diffraction pattern of as-cast Mg5Al-2SiX alloys With addition of Sr or Sb, finely distributed polygonal type Mg2Si particles are formed at the interfaces of liquid-solid phase during solidification, thereby it might restrain further growth of αMg matrix grain.
It may be resulted in three aspects : (1) the suppression of formation of thermally unstable β phase [6] ; (2) morphology modification of Mg2Si from coarse Chinese script to refined polygonal shape; (3) distribution of larger number of refined Mg2Si particles with thermal stability distributed in the grain boundary and pinning the grain boundary sliding during creep.

In this study, we succeeded in developing a white, opaque ultra-thin HAp sheet by means of increasing the surface roughness of the sheet, and of generating the inner grain boundaries of the sheet to enhance the diffused reflection of light.
In the lower ranges of the sintering temperatures, the grain size of the targets was coarse and the binding between grains was loose.
On the contrary, in the higher ranges of the sintering temperatures, the grain size of the targets was fine and the binding between grains was tight.
These phenomena is caused by the fact that, lower density PLD targets have weaker binding between particles, and therefore, produces a higher number of larger ablated particles relative to those of higher density PLD targets.
Furthermore, it was determined that the increments in the whiteness of the sheet is due to the generation of the inner grain boundary caused by the post-annealing process and the increase in the diffused reflection of the light.

Comparing with AZ91, the microstructure of these alloys was refined, the reticular grain boundaries gradually become discontinuous, and appear as skelecton and strip, also there are some grain phases appear.
With the increasing of the Y content, these phenomena become more evident, but when the content of Y is more than 0.9%, the alloy microstructures coarsen and the grains tend to agglomerate.
Results of EDS analysis of AZ91 containing 0.2%Ba and 0.7%Y The results of EDS analysis to the Fig.1c grain structure as shown in Fig.2 indicates that Mg, Al, Y and Ba are the main composing elements, but the content of Ba is low.
This grains are concluded to be constituted by intermetallics Al2Y and Mg17Al12 according to the previous experiments [5].
These alloys are numbered as alloy.1, alloy.2, alloy.3 and alloy.4 according to the Ba content from 0% to 0.3%.

Each composite grain must be well exchange decoupled from its neighbouring grains, but the exchange coupling of the two regions of the same grain must be very well controlled.
The exchange decoupling of neighbouring grains is achieved through O2 and Si doping, because SiO2 tends to segregate to grain boundaries.
The switching of grains is a two-step process [5,14].
Grain structure of SAF-ECC media [36].
Acknowledgements This work was supported by a grant of the Romanian National Authority for Scientific Research, CNDI– UEFISCDI, project number PN-II-PT-PCCA-2011-3.2-0373.

In order to evaluate material damages caused by thermal shock, several parameters may be adopted: number of thermal cycles required for the beginning of cracking, mass variation after determined the number of cycles, porosity variation with respect to the number of cycles, flexural strength before and after thermal shock, crack propagation by an indentation test, and also monitoring of properties like Young’s modulus and permeability [[] S.
This stabilization occurs due to formation of short cracks, which are interpreted as fissures which length is comparable to grains size or other microstructural characteristics.
As these samples present a similar behavior with respect to density and the initial modulus, this difference might be related to microstructure, since samples sintered at 1950 ºC have a larger grain size (Fig. 11), determined by studying grain size distribution with Quantikov software.
Vol. 472 (2008), p. 237. ], a microstructure with elongated grains and higher aspect ratio may generate some toughness mechanisms caused by crack deflection or bridging.
This samples presented greater grain sizes, which might have led to toughness mechanisms, thus reducing the damage caused by thermal shock.

The variations in grain size and formation of brittle phases due to transformation of δ ferrite during testing in welds are used to illustrate the effect of microstructural changes on crack initiation and propagation and fatigue life.
The stress concentration associated with the intersection of planar slip bands with the grain boundaries contributed to internal grain boundary cracks and a reduced fatigue life.
Further, the fatigue life was found to decrease due to oxidation at strain rates less than 3 × 10-3 s-1 at 823 and 873 K and due to combined effects of DSA and oxidation at 773 K (Fig. 3). 1000 10000 0.001 0.010 773 K 823 K 873 K STRAIN RATE: 3x10-3s-1 NUMBER OF REVERSALS TO FAILURE PLASTIC STRAIN AMPLITUDE Fig. 2 Fatigue Life of mod.9Cr-1Mo at various temperatures 10 -3 10 -2 400 600 800 1000 1200 773 K 823 K 873 K NUMBER OF CYCLES TO FAILURE STRAIN RATE (s -1 ) Fig. 3 Fatigue life of mod.9Cr-1Mo at various strain rates Ingress of oxygen and oxidation of surface-connected grain boundaries and slip bands were observed at lower strain amplitudes and lower strain rates of testing.
However, in weld joints, crack initiation occurs intergranularly in the HAZ (Fig. 4) where grain growth has occurred during welding.
Material Qualification The accumulated information from a large number of tests with appropriate statistics has been used to generate the fatigue curves.

A number of films have been prepared by changing the molarity of the precursor solution.
In order to get good quality, and various grain sizes, the molarity of the precursor solution was changed.
This provided information regarding the surface morphology of the films and could be used to investigate the nature of the deposited thin films: e.g., the roughness and size of the grains.
From the micrographs, one can see total coverage of the substrate with uniform grains.
The values of grain size and roughness were found to increase with increase in molarity of the precursor solution.

The large number, and high quality, of the papers making up this collection reflect the continuing vigor of the powder-metallurgy industry and associated research all over the world.

The contents are divided into the chapters: Powder Manufacturing, Mechanical Alloying, Powder Compaction, Powder Injection Moulding, Powder Forging, Spray Forming, Rapid Prototyping, Sintering, Post-Sintering Processes, Steels, Light Alloys, Composite Materials, Porous and Cellular Materials, Ceramic Materials, Diamond and cBN Tools, Hard Materials, Refractory Materials & Heavy Alloys, Magnetic Materials, Nano & Ultra-fine Grained Materials, PM Materials for Electrical and Electronic Applications, Functionally Graded Materials, PM Materials for Aerospace Applications, Superconducting Materials, Test and Evaluation, PM Production Equipments, Prospects of PM Research & Industry.

Results of laboratory tests have been statistically evaluated and completed with graphical records of carrying capacity of connections in tension corresponding to number of loading cycles.
Samples failure was caused by exceeding the timber strength in tension perpendicular to the grain.
For decreasing the probability of the crack occurrence during sample testing, reinforcement should be in the direction perpendicular to the grain [6, 7].
As the number of samples is small, the presented results are prone to statistical error.
Aknowledgement This paper has been achieved with the financial support of the Ministry of Education, Youth and Sports of the Czech Republic – funds of conceptual development of science, research and innovation assigned to VŠB-TU Ostrava in 2013 under identification numbers SPP IP2213314.

This RP phase with a general formula of (AO)(AMO3)n consists of n number of AMO3 perovskite blocks, separated by AO rock salt [6].
Fig. 3 and Table 1 represent SEM micrographs and average grain size of sintered compositions.
The average grain size of sintered Sr3Fe2O7-δ is 3.69 µm (stdv. 1.34 µm) as shown in Table 1.
The substitution of Co into Fe site tends to increase the grain size of Sr3Fe2O7-δ as illustrated in Fig. 3b-f.
The grain size of Sr3FeCoO7-δ increases to 10.94 µm (stdv. 3.41 µm).