Abstract: Low temperature sintering (Ni/Mn)CuZn ferrite was employed at most cases due to its
co-firability with Ag (below 960 °C).The purpose of this study is to fabricate (Ni/Mn)CuZn ferrite
sintered body with high-strength and high-frequency magnetic properties. Following is the
procedure: firstly, (Ni/Mn)CuZn ferrite powder was synthesized under CO2 atmosphere at 500 °C
from the mixed doxalate synthesized by co-precipitation method; then a small amount of boric acid
[H3BO3] was added to the powder, and the (Ni/Mn)CuZn ferrite powder compact was prepared with
Newton press and CIP methods; finally, (Ni/Mn)CuZn ferrite sintered body was fabricated by
sintering at 900 °C under CO2 atmosphere. By this method, NiCuZn and MnCuZn ferrite sintered
bodies with 0.5 mass% boric acid were obtained, the strength are 430 and 530 MPa respectively.
The effect of various Mn addition on NiCuZn electromagnetic properties were studied.
Abstract: Mechanical properties of tungsten heavy alloys are dependent on many factors including
the purity of the raw materials, their tungsten content, manufacturing parameters and the
microstructure of the final compact. The main object of this research was to examine the effect of
sintering conditions (temperature and time) on the microstructure of tungsten heavy alloys and how
the resulting modification of the microstructure can be used to optimize their mechanical properties.
Alloys composed of 88%, 93% and 95% wt. of tungsten with the balance of Ni: Fe in the ratio of
7:3 were consolidated into green compacts. Samples of each of the three resulting alloys were
sintered at different temperatures (1350°C,1450°C and 1500 0C) for different sintering holding
times (3 and 30 minutes) in hydrogen atmosphere. Standard metallographic procedures were used to
obtain SEM micrographs. The mechanical properties of tungsten heavy alloys were found to be
dependent on the microstructural parameters such as W particle size, solid volume fraction,
connectivity and w-w contiguity. It was shown that the mechanical properties of the alloys, and
especially their ductility, are harmed when tungsten grains are contiguous.
Abstract: 1mm-thick BLT ceramics were sintered in accordance with a bulk ceramic fabrication
process. All XRD peaks detected in the sintered ceramics were indexed as the Bi-layered perovskite
structure without secondary phases. Density was increased with increasing the sintering temperature
up to 1050°C and the maximum value was about 98% of the theoretical density. The remanent
polarization (2Pr) value of BLT ceramic sintered at 1050°C was approximately 6.5 μC/cm2 at the
applied voltage of 4.5kV. The calculated electromechanical couping factor (kt) of it was about 5%
and the mechanical quality factor (Qm) was about 2200. From these results, a BLT ceramic target
for plused laser deposition (PLD) system was successfully fabricated.
Abstract: Growth behavior and kinetics of grains in a liquid matrix has been studied by computer
simulation for various physical and processing conditions. The kinetics of growing and dissolving
grains is considered to follow that of single crystals in a matrix. Depending on the crystal shape, i.e.
rounded or faceted, different kinetic equations were adopted for growing grains and a single
equation was assumed for dissolving grains. Effects of critical parameters such as step free energy,
temperature, and liquid volume fraction were evaluated.
Abstract: The directions of further developments in the modeling of sintering are pointed out,
including multi-scale modeling of sintering, on-line sintering damage criteria, particle
agglomeration, sintering with phase transformations. A true multi-scale approach is applied for the
development of a new meso-macro methodology for modeling of sintering. The developed
macroscopic level computational framework envelopes the mesoscopic simulators. No closed
forms of constitutive relationships are assumed for the parameters of the material. When a time-step
of the calculations is finished for one macroscopic element, the mesostructures of the next element
are restored from the initial state according to the history of loading. The model framework is able
to predict the final dimensions of the sintered specimen on a global scale and identify the granular
structure in any localized area for prediction of the material properties.
Abstract: The removal of oxygen during sintering by carbothermic reduction and the resulting
carbon loss were studied for steel compacts prepared with the compositions Fe-3%Cr-0.5%Mo-
0.5%C and Fe-1.5%Mo-0.5%C, respectively, prepared from prealloyed powders. The compacts
were prepared by pressing at 600 and 1000 MPa, and sintering was done at 1100 and 1300°C in
vacuum. It showed that for the Cr-Mo steel, deoxidation strongly depends on the sintering
temperature, in contrast to the plain Mo steel; at 1300°C very low oxygen levels were measured
with the standard density compact while after pressing at 1000 MPa, still significant oxygen is
contained, which is in agreement with the lower carbon loss measured. This indicates inhibition of
final deoxidation by pore closure; nevertheless, the impact energy was very high and exceeded that
of the Mo alloyed steels, indicating that finely dispersed oxides within the matrix are irrelevant if
only the surface oxides have been completely removed.
Abstract: The particulate dispersive strengthened Cu-MoSi2 composites were prepared by a powder
metallurgy process with aim to develop novel copper based composites of reasonable strength, high
thermal conductivity and low thermal expansion coefficients. Compacted samples were sintered to
over 90% of theoretical density. Microstructure of the composites was investigated by SEM while
mechanical properties such as tensile strength, elongation and thermal properties such as thermal
conductivity and thermal expansion coefficient (CTE) of the composites were examined as a
function of the MoSi2 content and the process of fabrication. A comparative analysis of the
mechanical and thermal properties of various Cu-matrix composites currently in use was given and
the strengthening mechanisms for the Cu-MoSi2 composites were discussed.
Abstract: The nano-sized Fe powders were prepared by plasma arc discharge (PAD) process
using pure Fe rod. The microstructure of the prepared nanopowders was evaluated and the effect of
hydrogen gas in the chamber atmosphere was investigated. In addition, the sintering behavior of
nanosized Fe powders was analyzed and compared with those of conventional micron powders. The
prepared Fe nanopowders had nearly spherical shapes and consisted of metallic core and oxide shell
structures. In PAD nanopowder sintering, the higher volume shrinkage at low sintering temperature
was observed due to the reduction of surface oxide. The PAD nanopowders showed 6 times higher
densification rate and more significant isotropic shrinkage behavior than those of micron sized Fe
Abstract: A new process of pulsed electric current sintering was developed. It combines
compaction with activated sintering effectively and can manufacture bulky nano-crystalline
materials very quickly. Pulsed electric current sintering of high-energy ball-milled nano-crystalline
iron-based powders is investigated in this work. A nanostructured steel is obtained with high
relative density and hardness by this process. The average grain size of iron matrix is 58nm and the
carbide particulate size is less than 100nm. The densification temperature of ball-milled powders is
approximately 200°C lower than that of blended powders. When the sintering temperature increases,
the density of as-sintered specimen increases but the hardness of as-sintered specimen first
increases and then decreases. Microstructure analysis results show that the decrease of hardness is
caused by the dramatic grain growth of iron matrix.
Abstract: This paper concerned with SPS (spark plasma sintering), hot pressing of sinter nanometer
WC-Co powder and discussed the density, hardness, microstructures and grain sizes of the alloys
sintered by different styles. The results showed that SPS could lower the sintering temperature,
increased the density and circumscribed the growth of grain size of WC. Hot pressing sintering
could produce high density alloys and play well on the grain growth, but its sintering temperature
and sintering time were larger than SPS. Besides, the hardness of the sintered cemented alloys that
was dependent on the grain size and densification could also be improved by SPS and hot pressing.