Abstract: The oxide layer that usually covers the surface of liquid aluminum and its alloys, is one
of the main factors that hinders infiltration of these alloys into graphite particle compacts. The
oxide film increases the threshold pressure for infiltration and the porosity of the resulting
composites is large because the wetting at the metal/carbon interface is reduced. Infiltrating
graphite compacts with tin requires, however, a much lower pressure, less than half of that required
to infiltrate the eutectic Al-12Si alloy. As the surface tension of tin is half that of the Al-12Si alloy,
this result indicates that wetting at the Sn/C interface is slightly better. As a result, porosity in the
infiltrated samples is reduced. In order to reduce the threshold pressure and improve the properties
of Al-Si/graphite composites, a novel method has been used in this work that consists in placing a
thin film of tin at the compact end through which infiltration takes place. During the infiltration
process the graphite particles are firstly infiltrated by tin, which is pushed by the aluminum alloy,
thus avoiding the oxidation of the latter. The method proved to be very effective in reducing the
threshold pressure, while keeping almost constant the infiltration rate.
Abstract: Multi-layered composite sheet materials with nominal composition of Ti-46Al-9Nb
(at.%) were successfully processed from Ti, Al and Nb elemental foils using the cold roll bonding
technique. To promote the formation of intermetallic compounds in these composites, annealing at
600°C was employed for specimens subjected to various amounts of reduction. The microstructures
and phases that formed after cold rolling, the first annealing stage, and the second annealing stage
were characterized using scanning electron microscopy (SEM) equipped with an energy dispersive
x-ray spectrometer (EDS), transmission electron microscopy (TEM), and x-ray diffraction (XRD).
Good bonding was achieved for all rolled samples with a threshold reduction in thickness of about
35% in the first rolling pass. No new phases were formed in the cold rolling stage. Annealing stage
did promote the formation of the TiAl3 and NbAl3 phases at the interfaces.
Abstract: The wear behavior of unreinforced as well as feldspar particles reinforced copper alloy
(phosphor-bronze) composites was studied as a function of sliding speed and applied loads under
unlubricated conditions. The content of feldspar particles in the composites was varied from 1-
5% by weight in steps of 2%. A pin-on-disc wear tester was used to evaluate the wear rate.
Loads of 20-160 N in steps of 20 N and speeds of 1.25, 1.56, and 1.87 m/s were employed. The
results indicated that the wear rate of both the composites and the alloy increased with increase
in load and sliding speed. However, the composites exhibited lower wear rate than the alloy. It
was found that above a critical applied load, there exists a transition from mild to severe wear
both in the unreinforced alloy and in the composites. But the transition loads for the composites
were much higher than that of the alloy. The transition loads increase with the increase in weight
% of feldspar particles, but decreases with the increase in sliding speeds.
Abstract: The effects of V substitution for Cr to the sintering behavior of Cr containing Mo2NiB2
ternary boride base cermets and Mn addition to the mechanical properties and microstructure of the
Cr and V containing cermets were investigated by using Ni-5.0B-51.0Mo-(17.5-x)Cr-xV (mass%)
and Ni-5.0B-51.0Mo-12.5Cr-5.0V-(0-1.5)Mn (mass%) model cermets.
10mass%V substitution for Cr in the Cr containing cermets markedly improved transverse
rupture strength and hardness from 2.27 to 2.94GPa and from 85.3 to 87.2RA respectively and
refined the microstructure by retarding the progress of sintering especially at liquid phase sintering
stage. Small amount of Mn addition to the Cr and V containing Mo2NiB2 base cermets
significantly improved the sinterability and increased the mechanical properties of the cermets.
Abstract: FeAl-TiB2 composites have been combustion synthesized from mixtures of
Fe, Al, Ti and B powders. When the powder mixture was heated in vacuum to
approximately 900 K, an abrupt increase in temperature was observed, indicating that
the combustion synthesis reactions occurred in the powder mixture. X-ray diffraction
analyses revealed that the combustion-synthesized sample consisted of only FeAl and
TiB2. Metallographic investigations using a scanning electron microscope revealed that
fine TiB2 particles were dispersed in FeAl matrix phase. As the volume fraction of the
TiB2 particles increased from 0.3 to 0.8 by controlling the powder mixture composition,
the average TiB2 particle size increased to 1 to 7 μm and the average Vickers hardness
of the composites increased from 800 to 1600. This method has been applied to the
fabrication of some other ceramic particle dispersed metal matrix composites such as
Fe-TiC and FeAl-TiC systems.
Abstract: Copper-based high strength nanofilamentary wires reinforced by Nb nanofilaments are
prepared by severe plastic deformation (repeated hot extrusion, cold drawing and bundling steps)
for the winding of high pulsed magnets. The effects of microstructure refinement on the plasticity
mechanisms were studied via nanoindentation, in-situ deformation in TEM and under neutron
beam: all results evidence size effects in each nanostructured phase of the nanocomposite wires, i.e.
single dislocation regime in the finest regions of the Cu matrix and whisker-like behaviour in the
Nb nanofilaments. The macroscopic high yield stress is thus the results of the combination of the
different elastic-plastic regimes of each phase that include size effects.
Abstract: Room-temperature dry sliding wear behavior of hot-pressure sintered monolithic Co, Co-
20 wt.% CuSn and Co-20 wt.% WC composites were investigated. Wear tests of the materials were
carried out using a pin-on-disk wear tester at various loads of 10N-100N under a constant sliding
speed condition of 0.38m/s against glass (83% SiO2) beads. Sliding distances were varied with a
range of 100m-600m. A scanning electron microscopy was used to examine worn surfaces, cross
sections, and wear debris. X-ray diffraction (XRD) was utilized to identify phases of the specimen
and wear debris. All specimens exhibited low friction coefficients ranging from 0.12 to 0.4. The
sintered Co exhibited distinctive wear that was characterized by shallow dug canals on worn surface,
a very thin detaching surface layer, and fine debris. Thermal transformation of the Co specimen
from ε (hcp) phase to α (fcc) phase occurred during the wear of the Co, which was inferred from
XRD analysis of the wear debris. The transformation was suggested to cause the thin detaching
surface layer and the fine wear debris of the sintered Co. The wear of the Co-CuSn composite
proceeded by shear deformation of the CuSn particles, while WC particles of the Co-WC composite
sustained most of the applied load, which resulted in the low wear rate with fine wear debris of the
Abstract: Composites materials consisting of pure copper reinforced with 1 vol.% of NbC were
prepared by the powder metallurgy route to determine the influence of the milling process on the
mechanical and electrical properties. For comparative purpose different milling times at four
different rotational speeds were used. The resulting powders were consolidated by hot uniaxial
pressing under 90MPa for 2h at 923K to obtain materials with a fine microstructure without residual
porosity. It was found that the microstructure and properties of composite materials could be
principally related to the amount of Fe, Cr, C and O incorporated as impurities during the milling
process. Therefore, the rotational speeds used for milling has an important influence on the
properties of the final product. A lower energy-ball milling is accompanied by a smaller amount of
impurities (Fe, C and O) incorporated during milling. Composites materials combine electrical
conductivity above 40% IACS with high strength. A detailed microstructural analysis by scanning
and transmission electron microscopy and X ray diffraction showed that these properties are related
not only to NbC particles, but also to the presence of very fine particles of carbides and oxides.
Abstract: Due to excellent oxidation and corrosion resistance at elevated temperature, oxide ceramic
could be the preference served at high temperature oxidizing atmosphere over a long period of time.
In recent years, alumina-based eutectic in situ composite prepared by various solidification
techniques, which has superior properties even close to the melting point about 2100K, has been paid
much attention. In this paper, Al2O3/YAG/ZrO2 ternary eutectic and hypoeutectic ceramics are
prepared from melt by laser zone-remelting technique, the rapid solidification characteristic and the
mechanical property of the composites are investigated. The results show that: (1) Compared to
sintered composite with the same composition, laser zone-remelted Al2O3/YAG/ZrO2 eutectic in situ
composite has different microstructure showing fine interpenetrated network with Al2O3, YAG and
ZrO2 phases continuously intergrown, while none of pores, grain boundaries and amorphous phases
is found. (2) The scanning rate and the power density of the laser beam has strong effect on the
microstructure morphology. When the power density is determined, the eutectic spacing is reduced
with the scanning rate increased. The characteristic eutectic spacings and phase sizes of YAG and
Al2O3 are about 2~3μm, and the characteristic dimension of ZrO2 is less than 1μm. (3) The hardness
and the room-temperature fracture toughness of Al2O3/YAG/ZrO2 eutectic are respectively
Hv=16.7±2.0 GPa and KIC=8.0±2.0 MPa.m1/2, and those of hypoeutectic are respectively
Hv=15.8±2.0 GPa and KIC=3.9±1.0 MPa.m1/2.
Abstract: The crystal structure of metastable phase in Ag added Al-Mg-Si alloy was investigated
by comparing the β’-phases in Al-Mg-Si alloy without Ag, using images of high resolution
transmission electron microscope (HRTEM), selected area electron diffraction patterns (SADPs)
and an energy dispersive X-ray spectroscopy (EDS). SADPs and HRTEM images obtained from
metastable phase in the Ag added Al-Mg-Si alloy showed similar to those of β’-phase in Al-Mg-Si
alloy without Ag and had different lattice spacings because of the effect of Ag. According to our
careful analysis on obtained HRTEM images and SADPs, it includes more complicated crystal
lattice of distorted hexagons.