Search results

The powder metallurgy(PM) superalloy has shown highly homogeneous structure containing fine grains, annealing twins and prior particle boundaries (PPBs) as well as brittle MC carbides [9].
Maybe more important, it is evident from Fig. 4(b) that the MC contains a number of stable oxides ZrO2 with an average diameter of 20nm as the nuclei accelerate the preferential precipitation of carbides which forms the continuous harmful PPBs.
Effect of oxygen content on impact toughness of a fine-grained magnesium alloy, Materials Letters. 65 (2011) 2995-3001

Attention was paid to select the particle grain size so that it was not larger than 1/7 times the width of the arch.
The mechanical properties of rammed earth material, representative of the one used to realize the arches, have been determined with uniaxial compression tests on five cubic specimens of 80x80x80mm3 made of rammed soil, from which grains larger than 8mm were removed with an ASTM sieve, and 11% of water calculated with respect to the dry weight of the earth.
For this reason, it was possible to build a limited number of models and some difficulties were met in the control of initial constraints.

The additional layer (dark etching layer) observed between the compound layer and diffusion zone appears to be columnar grains of γ' (Fe4N) + α-Fe.
Precipitates along prior austenite grain boundaries near the surface were all coarser than the precipitates observed at the core of the treated samples.
The number of cracks was particularly high for the samples treated at 550 and 580 0C (Fig. 3(c) and 3(d)).

There are no grain boundary and dislocation in their structure therefore they exhibit superior properties when compared with similar crystalline counterparts.
Results show that under the same drilling conditions the micrograin carbide tool, submicron size carbide grains in it, generally requires less thrust force than solid one.
Acklowledgement A portion of this research was sponsored by The Scientific and Technological Research Council of Turkey (TUBITAK) under the project number 107M443.

Cr2O3 particles can be as dislocation sources, are able to increase the density of dislocations, and block the movement of dislocations on grain boundaries and sub-boundaries, thereby improving the strength of the Cr2O3/Cu composites [9].
Owing to the presence of uniformly dispersed and high electrical erosion-resistant Cr2O3 particles, a great number of particulates composed of copper-coated Cr2O3 particles form on the surface and in the matrix of Cr2O3/Cu composites.
Fig.5 EDS of the worn surface of 1.1Cr2O3/Cu composite（45N,5m/s,30A) In the Cr2O3/Cu composites prepared by internal oxidation of Cu-Cr alloy, the dispersed Cr2O3 nanoparticles serve as sources of dislocation to increase its density, which exert pinning effects on the dislocation and grain boundaries during deformation and annealing treatment.

Fig. 1 Particles size distribution of Al2O3 powder The morphology of the grains of Al2O3 at 250 °C and 900 °C, was observed by scanning electron microscopy (Fig. 2).
This indicates that the oxidation heat treatment does not affect the grain morphology.
Fig. 3 Adsorption isotherms of water vapor onto Al2O3 samples at 25 °C Depending on whether 10.6 Å2 or 14.8 Å2 area can be taken by a water molecule [19], from the amount of adsorbed water vapor and the cross sectional-area of the polar head, it is possible to calculate approximately the hydrophilic and hydrophobic parts of the alumina samples surface according to the following equation: S=Na×Γads×σ (1) Where: Na is the Avogadro’s number; Γads: the amount of adsorbed vapor water (µmol.g-1); s : area of gas molecule (Å2), with: s H2O = 10,6 Å2 or 14,8Å2 and s C4H10 = 44.6 Å2 The values of hydrophilic and hydrophobic surface areas obtained are listed in Table 2 and 3, successfully.

., TM-D, average grain size 0.19mm, a-alumina) and Y3Al5O12(YAG) (Shinetsu Chemical.
Ltd., RYAG-OCX-076, average grain size 1.1mm) powder (weight ratio; 95:5) were used as raw materials for the green sheet.
Number of bending strength measurement was 15~17, and the Weibull modulus of the maximum strength was obtained.

The constitutive relations of an isotropic linear poroelastic medium can be expressed as ij kkij ij Gεελδσ 2 ' += (4) in whichλ is Lame's constant, G is the shear modulus in Pa, ν is the Poisson's ratio, δij is the Kronecker delta defined as 1 for i=j and 0 for i≠j, and the effective stress tensor in Eq.(4) is also given by the relation pijijij αδσσ −=' (5) where σij is the total stress tensor in Pa, α is the Biot's effective stress coefficient which depends on the compressibility of the constituents, which is a positive constant equal to 1 when individual grains are much more incompressible than the grain skeleton, and p is the pore fluid pressure in Pa, negative for suction.
These numerical results are supported by a number of experimental observations reported in the literature [18]. 0 0.05 0.1 0.15 0.2 0.25 0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 Strain Permeability/(m 2/(MPa2d)) m=1.5 m=3 m=5 Fig. 2 Simulated permeability-strain curves Fig. 4 (a) Simulated rock failure process, (b) gas pressure gradients, (c) AE counts, and (d) the volume of flow for rock specimen (m=1.5) As we know, one method of observing damage or microcracking during rock deformation experiments is by monitoring the acoustic emissions (AE) or seismic events produced during deformation.

To remedy this, a number of wires is placed next to each other.
As long as the stress on the different lattice planes doesn’t vary to much as a result of grain-grain interactions, the calculated value for the stress is considered to be a reasonable approximation for the stress in the cementite phase.

For the assessment, the sum of the openings along the glue line and at the end grain developed during the tests has to be taken in relation to the total glue line length at the end grain of the specimen.
Table 1: Test program for delamination and shear tests Series Test method Standard Shape Sizes [mm] Number Material Adhesive 01 Delamination EN 391-A Block b/h/l = 160/320/75 51 GL28k-spruce PUR 02 Delamination EN 391-A Block b/h/l = 160/160/75 42 GL24k-spruce MUF 03 Delamination EN 391-A Core Ø 35, l = 80 17 GL28k-spruce PUR 04 Delamination EN 391-A Core Ø 35, l = 80 14 GL24k-spruce MUF 05 Shear test EN 392 Core Ø 35, l = 80 51 GL28k-spruce PUR 06 Shear test EN 392 Core Ø 35, l = 80 42 GL24k-spruce MUF 07 Shear test EN 392 Core Ø 35, l = 80 9 GL24h-spruce RF 08 Shear test EN 408 Block b/h/l = 32/55/300 9 GL24h-spruce RF 09 Shear test - Block b/h/l = 160/200/200 17 GL28k-spruce PUR 10 Shear test - Block b/h/l = 160/200/200 14 GL24k-spruce MUF 11 Shear test - Beam b/h/l = 160/320/1350 17 GL28k-spruce PUR 12 Shear test - Beam b/h/l = 160/160/800 14 GL24k-spruce MUF 13 Shear test - Beam b/h/l = 80/120/650 9 GL24h-spruce RF Experimental results Delamination tests according to EN 391