Abstract: The increasing demand of PM parts for automobile and aerospace applications has
caused a strong development of the aluminium based metal matrix composites (MMCs).Aluminium
alloys are one of most widely used materials as matrix in MMCs, both in research and development
as well as in industrial applications. The main reason is the combination of good specific properties,
the first requirement in most applications, and the competitive price compared to other low density
alloys such as Mg or Ti alloys.
In the present work, the influence of the ceramic reinforcement addition to a 2xxx series
aluminium alloy is studied. Several percentages of TiCN have been added to the Al-Cu alloy using
PM techniques, in order to analyze its influence on the liquid phase sintering process and also on
the final properties of the material. The materials have been uniaxially compacted using two
different pressures to determine the optimal pressing condition. They have been subsequently
sinterized in a N2-H2 atmosphere.
Analysing the results obtained, it can be concluded that the addition of TiCN allows a better
distribution of the liquid phase up to the 10 %wt, where the optimal results are observed: For higher
quantities of reinforcement, elemental copper is observed in the microstructure with the consequent
decrease in densification.
Abstract: Investigation results of the heat treatment effect on the corrosion resistance of the EN
AW-AlCu4Mg1 (A) aluminium alloy base composite materials reinforced with the Ti(C,N)
particles with varying volume fractions are presented. Examinations were made of the EN AW-Al
Cu4Mg1(A) aluminum alloy, and also of the composite materials with the matrix from this
aluminium alloy. It was found out, basing on own research, that corrosion wear after the corrosion
tests of the composite materials with the addition of 5% of the Ti(C,N) particles is smaller
compared to the pure aluminium alloy. Precipitation hardening causes improvement of the corrosion
resistance of the investigated composite materials and - like in the state before the heat treatment,
materials with 5% portion of the Ti(C,N) reinforcement ratio are characteristic of more
advantageous features compared to the material without the reinforcement.
Abstract: The aging behavior of sintered Al composites with various ceramic contents was
investigated. 2xxx series blended powder was used as the starting powder. Ceramic contents were 0
wt.% and 5 wt.%. The blended powders were compacted at 250 MPa. The sintering process was
performed at 620oC for 60 min in a N2 atmosphere. After sintering, each part was solution-treated at
518oC for 60 min and aged at 180oC. The Rockwell hardness value at the peak aging time increased
with increased ceramic contents. However, the peak aging time at maximum hardness was reduced
with increased ceramic contents. The changes in aging behavior may have been caused by the
acceleration of diffusion due to the strain induced by differences in the thermal expansion
coefficients of the matrix and the ceramic phases.
Abstract: Electronic packaging involves interconnecting, powering, protecting, and cooling of
semiconductor circuits for the use in a variety of microelectronic applications. For microelectronic
circuits, the main type of failure is thermal fatigue, owing to the different thermal expansion
coefficients of semiconductor chips and packaging materials. Therefore, the search for matched
coefficients of thermal expansion (CTE) of packaging materials in combination with a high thermal
conductivity is the main task for developments of heat sink materials electronics, and good
mechanical properties are also required.
The aim of this work is to develop copper matrix composites reinforced with carbon nanofibers.
The advantages of carbon nanofibers, especially the good thermal conductivity, are utlized to obtain
a composite material having a thermal conductivity higher than 400W/mK.
The main challenge is to obtain a homogeneous dispersion of carbon nanofibers in copper. In
this paper, a technology for obtaining a homogeneous mixture of copper and nanofibers will be
presented and the microstructure and properties of consolidated samples will be discussed.
In order to improve the bonding strength between copper and nanofibers, different alloying
elements were added. The microstructure and the properties will be presented and the influence of
interface modification will be discussed.
Abstract: Mechanical properties of 7xxx series Al metal matrix composite (MMC) powders
containing different amounts of ceramic were investigated. The ceramic contents of the starting
powders were 5 wt.% or 10 wt.%. 7xxx Al blended powder was used for comparison. The powders
were uniaxially cold compacted using a cylindrical die with a compacting pressure of 250 MPa and
were sintered at 620oC in a dry N2 atmosphere for 60 min. The heating rate was varied up to
100oC/min. For the heat treatment, sintered parts were solution treated at 475oC and aged at 175oC.
Compression tests were conducted to reveal the effect of Al2O3 particle content on the mechanical
properties of the composites. Fractography was examined using a scanning electron microscope.
Abstract: The creep behavior of particulate Al-5vol.% SiC composite was investigated. The
composite powder was produced by mechanical milling and hot extruded at 450°C at the ratio of
16:1. A creep test was carried out at a constant load at 598, 648, and 673 K. Using the existing
equations proposed for the steady-state creep of metals, the threshold stress and the stress exponent
of the creep as a function of temperature were determined. The stress exponent was found to be 3 at
the temperature of 673 K and 8 at the lower temperatures, i.e. 598 and 648 K. The dependency of
the threshold stress to temperature obeys the Arrhenius relationship with the energy term of 29 kJ
Abstract: The preparation of Ti50Cu28Ni15Sn7 metallic glass composite powders was accomplished
by the mechanical alloying of a pure Ti, Cu, Ni, Sn and carbon nanotube (CNT) powder mixture
after 8 h milling. In the ball-milled composites, the initial CNT particles were dissolved in the
Ti-based alloy glassy matrix. The thermal stability of the amorphous matrix is affected by the
presence of the CNT particles. Changes in Tg and Tx suggest deviations in the chemical composition
of the glassy matrix due to a partial dissolution of the CNT species in the amorphous phase. The
bulk metallic glass composite was successfully prepared by vacuum hot pressing the as-milled
CNT/ Ti50Cu28Ni15Sn7 metallic glass composite powders. A significant hardness increase with the
CNT additions was observed for the consolidated composite compacts.
Abstract: In this study, aluminum-based composites reinforced with various amounts of α-Si3N4
were produced by powder metallurgy (P/M). The machinability properties of MMCs were
determined by means of cutting forces and surface roughness. Machining tests were carried out by
using PCD and K10 cutting tools. Increasing of Si3N4 volume fraction in the matrix resulted in a
decrease of the surface roughness and turning forces. PCD cutting tools showed better cutting
performance than K10 tools. Surface roughness and turning forces were decreased significantly by
Abstract: The composite used in this paper was prepared by hot-pressing ball-milled Mg alloy
powders, in which NiTi shape memory alloy fibers in a row were sandwiched. The microstructure
were examined by an optical microscope, scanning electron microscope, X-ray diffraction, and
transmission electron microscope to measure its microhardness and density. It is shown that the
composite consisted of a homogenous matrix with uniformly distributed NiTi shape memory alloy
fibers, where recrystallization took place in the Mg alloy matrix that was subjected to plastic
deformation. It is known that plastic deformation is beneficial to the refinement of the grains, that is
an adequate bonding forms between the matrix and fibers, the density of the composite increases
after the hot-forging; its tensile strength increases significantly because of the grain refinement; the
hot-forging process improves the properties of the NiTi shape memory alloy fibers reinforced Mg
Abstract: Sintered composites of Al-8wt%Cu-10vol%SiCp were deformed by repressing or equal
channel angular pressing(ECAP) at room temperature, 500°C and 600°C. Their microstructures and
transverse rupture properties were compared. Repressing produced more densification than ECAP
but ECAP resulted in much higher strengths than repressing. In both cases, the transverse rupture
strengths, after deformation at room temperature and 500°C, are much lower than those deformed at
600°C, despite of only slight differences in density. Fractured SiC particles were observed after the
deformation, very frequently at room temperature, less frequently at 500°C and rarely at 600°C.
Some interfacial de-bonding between the matrix and SiC particles were also observed particularly
in the ECAPed specimens. The higher bend strengths and less SiC fracturing at 600°C are
attributable to the presence of an Al-Cu liquid phase during deformation. ECAP at 500°C and 600°C
caused recrystallization and produced very fine grain structures. Grain refinement, as well as
enhanced bonding between particles due to high shear deformation associated with ECAP, is
considered the major reason for the much higher strengths. The employment of copper coated SiC
instead of bare SiC particles for preparing the composites was found not beneficial neither for
minimizing the particle fracturing nor for improving the properties.