Search results

A grain size distribution test of the soil was also performed to show the type and gradation of the soil.
The grain size distribution of the soil, which is used for the unfired soil lime bricks, spans from clay to medium grained sands. 60% of the soil, by mass, consists of fine to medium grained sands.
The same type of mixture and number of bricks was also employed for testing plain bricks (without any fiber addition).

By combination of AM and metal forming operations such as closed-die forging, novel process chains may be developed, offering the possibility to reduce the number of forging steps and to create near-net shape forgings with integrated features yielding the desired performance, microstructure and properties.
The initial microstructure of the as-built SLM samples reveals fine acicular martensite needles (α’-phase) within the β-grains.
The β-grains are elongated along the building direction.
The martensitic lath length corresponds to the width of the columnar grains.
The microstructure mainly consists of a lamellar α-phase and a small amount of β-phase within the prior columnar β-grains aligned along the build direction.

The Vickers hardness number, HV, is given by equation (3) below.
This data also was supported by [12] stated that the increasing in the yield strength and ultimate tensile strength can be attributed to the decrease in the grain size and hardening due to TiB2 particles.
The increase in hardness of the composites can be attributed to the decrease in the grain size to TiB2 particles.
The particles also were homogeneously distributed around the grain boundaries and also can be seen clearly in figure below.
[5] Mallikarjuna, C., Shashidhara, S.M., Mallik, U.S., Parashivamurthy, K.I. : Grain refinement and wear properties evaluation of aluminum alloy 2014 matrix-TiB2 in-situ composites.

At cooling times exceeding tc10/7 a respective grain boundary attack was observed at 10 x magnification.
Fig. 2: Continuous cooling/precipitation diagram (schematic), t,T = time,temperature, TSA = solution anneal temperature, TP = equilibrium temperature of precipitation (M23C6 or M2N), G = precipitation at austenite grain boundaries, D = discontinuous precipitation within the austenite grains, t10/7 = cooling time between 1000 and 700°C, tc10/7 = critical cooling time just avoiding detectable precipitation.
However, precipitation may occur along grain boundaries during subsequent quenching if the t10/7 cooling time stays above the critical one.
This is e.g. expressed by the pitting resistance equivalent number PREN = Cr + 3.3 Mo + k • N [mass%] [17, 18].

Calculation and Experimental Procedure With the selected power density and scanning speed, the metal bond is ablated and removed for getting grain exposure.
A number of laser processing parameters could thus be predicted.
As for laser dressing samples, they are metal-bond diamond wheels (grain granularity: 120�, grain content: 0.88 g/cm3).
Laser dressing that removes the metal bond through ablation of the bonding material to expose cutting grain edges.

The mean grain size was about 70µm and the grains were rather equiaxed.
For a polycrystalline metal the similar idea may be possible to adopt, that is the intra-grain dislocation structures such as dislocation cell develops during pre-straining and they becomes the resistance to the newly activated slip systems in a early stage of subsequent deformation, as be explained by Schmitt et al.[13] in sequential uniaxial tensions of copper sheets.
In a polycrystalline metal, the multiple slips and the interactions of dislocations on different slip systems often appear in grains, even in a monotonic straining.
For the larger angle α > 45° the number of newly activated slips systems is supposed to be larger thus enhances the latent hardening phenomenon.

A number of studies have been performed to address one or more of the issues contributing to the non-linear behavior of these composites.
Experimental evidence shows that advanced ceramics can have high macroscopic fracture toughness many times greater than the fracture energy for cleavage of their grains or for separating their grain boundaries.
This phenomenon is concerned with the heterogeneity in the micro-scale properties, such as at the grain level.
In considering the actual granular microstructure of particulate composites, it can be considered that microcracks are grain-facet sized, located and oriented.

The results showed that the oxidation film type of TiAl-based alloy depended on microstructure, especially, on grain size and distribution of γ/α2 phase.
Under high temperature,it is easier to form the protective Al2O3 film for microstructure with lamellar γ/α2 phase, in contrary to the microstructure with coarse equiaxed grains trend to forming un-protective TiO2 film.
Because the materials with bcc crystal structure have a relatively larger number of slip systems, the deformation is easily.
However, as-sintered sample of MA powder forms fine grains, the most of grain size is below 2µm.Obviously, the different state of milled powder and blend powder lead to different sintered microstructure.

After multiple firing, leucite crystal structure within the veneer porcelain changed obviously, which crystal grown up from grain (2 ~ 4 times) to short rod shape (6 times) to needle shape (8 times).
As far as leucite-based porcelain be concerned, repeated heat treatment process which was higher than glass transition temperature would effect the size and content of leucite grain.
According to manufacturer’s report, VITA-VM9 was a kind of leucite-based ceramic, its grain size (about 18µm) was smaller than that of traditional leucite porcelain (30µm) and gathered little, which was beneficial to retrain of crackle production between glass phase and crystal phase and maintenance of thermal stability of material.
Although using vacuum firing process, a large number of stomata still generated, which had something to do with gas release of melting silicate caused by multiple firing.
Leucite crystal structure in veneer porcelain changed obviously, the crystal grain grown up gradually.

A large number of gray inclusions are present on the surface of the B1 powder.
a)b)c)d) Figure 5 Microstructure of deposited Ti-6Al-4V samples from a) A1 b) A2 c) B1 d) B2 powders As can be seen from the figure 5, the structure in samples produced from powders A1 (45-100 μm) and B1 (45-100 μm) is more fine-grained.
In samples obtained from powder A2 (106-180 µm) and B2 (180-200 µm), the structure is coarse-grained.
In addition, the largest grain size corresponds to the powder with the largest particle size.
Increasing the particle size of the powder increases the grain size in the structure of the grown samples.