Abstract: Synchrotron X-ray microtomography has been utilized for the 3D characterisation of
microstructure of aluminium foams. A combination of phase contrast imaging technique and several
application techniques, such as local area tomography, microstructural gauging and in-situ
observation, has enabled the assessment of microstructural effects on compressive deformation
behaviours. It has been clarified that ductile buckling of a cell wall occurs regardless of any of the
above microstructural factors in the case of a pure aluminium foam, while rather brittle fracture of a
cell wall is induced by the existence of coarse micro-pores independently of the intermetallic particles
and the grain boundary in the case of Al-Zn-Mg alloy foams. When cooling rate during foaming is
high, however, lower energy absorption might be attributable to the significant amount of residual
foaming agent particle and its inhomogeneous distribution. These tendencies are also confirmed by
3D strain mapping by tracking internal microstructural features.
Abstract: The microstructure and oxidation resistance of MSi2-SiC or MSi2-Si3N4
nanocomposite coatings (M = Mo, W, Nb, Ta) on M substrates formed by displacement
reactions between M-carbides or M–nitrides and silicon, respectively, was investigated. Present
study demonstrated that the crack density formed in the MSi2-base nanocomposite coatings due
to mismatch in the coefficient of thermal expansion between nanocomposite coatings and M
substrates could be controlled by adjusting the volume fraction of the SiC or Si3N4 reinforcing
particles with the low CTE values. The high- and low-temperature oxidation resistance of
nanocomposite coatings was superior to that of monolithic MSi2 coatings.
Abstract: Experiments were conducted to evaluate the mechanical properties of a spray-cast Al-
7034 alloy processed by severe plastic deformation. The alloy was received with an average grain
size of ~2.1 μm and processed by equal-channel angular pressing (ECAP) at a temperature of 473 K
to give a grain size of ~0.3 μm after 6 or 8 passes. Following ECAP, the mechanical properties
were evaluated at room temperature (298 K) and at an elevated temperature of 673 K. In tensile
testing at ambient temperature, the stress-strain curves show very short regions of strain hardening
after ECAP and low values for the ultimate tensile strength by comparison with the unpressed alloy.
This lack of strength is due to the high pressures imposed by ECAP and the consequent
fragmentation and dissolution of the rod-like MgZn2 precipitates. It is shown that the strength may
be restored by performing an appropriate ageing treatment after ECAP. Superplastic ductilities
were recorded at a temperature of 673 K with tensile elongations exceeding 1000%. Careful
inspection of the polished surfaces of samples pulled to fracture in the superplastic condition
revealed the occurrence of extensive internal cavitation. Quantitative measurements showed the
development of these internal cavities is consistent with conventional superplastic alloys.
Abstract: Park et al. measured the deposition and annealing textures of nanocrystalline Ni and Ni- 20 % Fe electrodeposits. They found that the deposition texture of major <100> + minor <111> changed to the texture characterized by major <111> + minor <100> after annealing. They also found that the lattice constants of the <100> oriented grains in the as-deposited state were larger than those of <111> oriented grains. In this paper, a model has been advanced to explain the unusual results of lattice constants, and the texture transition has been discussed.
Abstract: The microstructure change by warm deformation in high-carbon steels with different
initial ferrite (α) + cementite (θ) duplex microstructures has been examined. Three kinds of initial
structures, i.e., pearlite, α+spheroidized θ and tempered martensite, were prepared using
Fe-0.8C-2Mn and Fe-1.0C-1.4Cr alloys and compressed by 30-75% at 973K at a strain rate of
5x10-4 s-1. Equiaxed fine α grains, approximately 2μm in diameter and mostly bounded by
high-angle boundaries, are formed with spheroidized θ by dynamic recrystallization during
compression of the pearlite by 75%. When the (α+θ) duplex structure containing spheroidized θ
was deformed, the original α grains become elongated and only subgrains are formed within them
by dynamic recovery. For the tempered martensite, equiaxed α grains similar to those in the
deformed pearlite were obtained after 50% compression. This indicates that the critical strain
needed for the completion of dynamic recrystallization of α is smaller for the tempered martensite
than for the other structures.
Abstract: In the last years a new clinical method to carry out surgical operations has been introduced.
It consists in minimally invasive vascular surgery (also called laparoscopy). In one hand, during
laparoscopy procedures, sutures cannot be handled with fingers, and the use of stainless-steel needle
holders is required. In the other hand, companies that fabricate sutures clearly mention that
metal-made devices should be avoided when manipulating the monofilaments. Therefore, the
manipulation of the suture monofilaments (made of polymers) by laparoscopic needle holders (made
of metals) is controversial. Literature in this field is limited and incomplete. Therefore, the aim of this
study was to investigate the mechanical and microstructural effects of the manipulations with
laparoscopic needle holder on polymeric suture monofilament. Surgipro© (polypropylene),
Teflene© (polyvinylidene fluoride) and Gore-Tex© (polytetrafluoroethylene) monofilament suture
were pinched with a standard clinical protocol by a surgeon. Scanning electron microscopy,
micro-mechanical testing, differential scanning calorimetry, x-ray diffraction, small angle x-ray
scattering and Fourier transform infrared spectroscopy were then performed. Results showed that the
ultimate tensile strength of Teflene and Gore-Tex sutures does not change after pinching whereas it
decreases significantly for Surgipro sutures. This is attributed to stress concentration and to the
compressive strength applied on the monofilament, which are closely related to the permanent
deformation of the suture after pinching. Teflene and Gore-Tex monofilament sutures showed to be
not affected even after severe pinching with laparoscopic needle holders. Therefore, our results
clearly showed that the use of Surgipro II sutures in laparoscopic interventions should be avoided.
Abstract: In the present work the precipitation behaviour and recrystallisation resistance of Alalloys
containing Hf, Sc and Zr in different concentrations and combinations have been
investigated. Special focus has been put on the Hf-containing alloys, as one of the objectives of this
work was to find out if Hf can be used as a replacement for Sc. Additions of Sc, either alone or in
combination with Zr, leads to the formation of coherent and homogeneously distributed dispersoids,
which very efficiently inhibit recrystallisation. Despite these attractive properties, the high price of
Sc has limited its use as an alloying element in aluminium. The present investigation has revealed
that Hf cannot fully replace Sc, as only heterogeneous dispersoid distributions are obtained in the
absence of Sc, i.e. in regions where the number density is low the alloys would still be prone to
recrystallisation. However, as an extra addition to the already remarkably stable Sc+Zr-containing
alloys, Hf can lead to further improvements and consequently open for the use of aluminium alloys
at very high temperatures. Al3(Sc,Zr,Hf)-dispersoids were present at the largest f/r-ratios and also
displayed lower coarsening rates than Al3(Sc,Zr)-dispersoids. Very promising results were obtained
for an Al-Hf-Sc-Zr alloy, which maintained mainly an unrecrystallised structure after extrusion and
large degrees of cold rolling.
Abstract: Ti–B–C–N and Ti–Si–B–C–N nanocomposite coatings were deposited on AISI 304
stainless steel substrates by DC unbalanced magnetron sputtering from two (80mol% TiB2–20mol%
TiC and 40mol% TiB2–60mol% TiC) composite targets in various Si target powers. The relationship
among microstructures, mechanical properties, and tribologiacal properties was investigated. The
synthesized Ti–B–C–N and Ti–Si–B–C–N coatings were characterized using x–ray diffraction
(XRD) and x–ray photoelectron spectroscopy (XPS). These analyses revealed that the Ti–Si–B–C–N
coatings are nanocomposites consisting of solid-solution (Ti,C,N)B2 and Ti(C,N) crystallites
distributed in an amorphous TiSi2, SiC, and SiB4 matrix including some carbon, BN, CNx, TiO2, and
B2O3 components. The addition of Si to the Ti–B–C–N coating led to percolation of amorphous TiSi2,
SiC, and SiB4 phases. The Ti–Si–B–C–N coatings exhibited high hardness and H/E values, indicating
high fracture toughness, of approximately 35 GPa and 0.098, respectively. Furthermore, the
Ti–Si–B–C–N coatings exhibited very low wear rates ranging from ~3×10-7 to ~16×10-7 mm3/(N·m).
The minimum friction coefficient of the Ti–Si–B–C–N coatings was approximately 0.15 at low Si
target power between 25W and 50W. A systematic investigation on the microstructures, mechanical
properties, and tribological properties of Ti–Si–B–C–N coatings prepared from two TiB2–TiC
composite targets and one Si target is reported in this paper.
Abstract: The distortion and the residual stress are the inevitable consequences of the welding and
these may reduce the strength and the quality of the welded structures. To prevent the harmful
influence of the welding distortion and the residual stress, their theoretical prediction is necessary.
However the existing methods are mostly developed for the study of specimens in laboratories.
Compared to the specimens, the structures manufactured in the industry are larger in size and more
complex in geometry. For the theoretical prediction applicable to industrial structures, more
powerful and practical methods are necessary. To achieve this goal, the authors developed a fast
computational method for thermal elastic plastic analysis and an elastic finite element method using
Abstract: Lotus-type porous metals with low thermal conductivity are fabricated by continuous
zone melting technique, which possess directional elongated pores. The porous metals have been
able to be fabricated through the conventional casting method by utilizing the solubility gap
between solid and liquid in pressurized gas atmosphere. However, there is a shortcoming that the
pores are coarsened in the part farther from the chill plate in the ingot. In order to overcome such a
shortcoming, we developed the continuous zone melting technique and successfully produced the
lotus-type porous metals with even low thermal conductivity such as stainless steel and superalloys.
Furthermore, from the viewpoint of mass production with low cost, we invented novel ”continuous
casting technique”. The molten metals dissolving gas are solidified continuously by passing through
the mold cooled with chiller and thus, lotus-type porous metal plate as long as one meter was
produced for short time. Sufficient uniformity of the porosity and pore size was obtained in such
long porous ingots. This technique is prospective method for commercial mass production.