Abstract: Rapidly solidified industrially stripcast Pb-Sb-Sn triboalloys showed microstructures
typical for the eutectic decomposition of metallic glasses. Evidence was found of crystallisation
above the glass transition temperature and ageing at room temperature. The observation supports a
previous hypothesis by the authors on the wear properties of soft tribological alloys.
Abstract: The non-homogeneous metal flow during the extrusion process is well controlled by
introducing a reflecting non-equilibrium parameter of metal flow —— the mean-square deviation of
velocity ( SDV ) in this paper. The finite deformation elastoplastic finite element method is used to
carry out the numerical simulation research on the profile extrusion process with the different
extrusion parameters (such as extrusion ratio, frictional factor). The varied laws of the extrusion
pressure, SDV and stress-strain fields with the extrusion parameters are obtained. It is a theoretic
consideration to optimize the technological parameters in the profile extrusion process.
Abstract: Board-level reliability of conventional Sn-37Pb and Pb-free Sn-3.0Ag-0.5Cu solder joints
was evaluated using thermal shock testing. In the microstructural investigation of the solder joints,
the formation of Cu6Sn5 intermetallic compound (IMC) layer was observed between both solders and
Cu lead frame, but any crack or newly introduced defect cannot be found even after 2000 cycles of
thermal shocks. Shear test of the multi layer ceramic capacitor (MLCC) joints were also conducted to
investigate the effect of microstructural variations on the bonding strength of the solder joints. Shear
forces of the both solder joints decreased with increasing thermal shock cycles. The reason to the
decrease in shear force was discussed with fracture surfaces of the shear tested solder joints.
Abstract: In this study, we investigate the crystalline states and conditions for the
grain-refinement of Bi70Sb30 (at.%) alloy. It was considered under an ultra strong gravity field, the
crystals were fine-grained from the primary grain sizes of several mm to several tens of mm, and
the crystal growth followed with formation of graded-composition structure due to sedimentation
of atoms along the direction of gravity. It was found that for the crystal-grain refinement in
Bi70Sb30 alloy the minimum gravitational field and the minimum time duration were at least
160,000 G and 10 hours, respectively at about 200 °C.
Abstract: In order to solve the contradiction found in the Hall-Petch behavior in the ultra-finegrained-
and nano-grained- materials, reinvestigation of the physical meaning of Hall-Petch
constants has become necessary. The present work is hence attempted to theoretically construct the
Hall-Petch slope constant, KH-P. This was carried out based on the principle of image analysis and
previous internal energy approach. After analyzing several influencing factors on the KH-P, a model
was established with 95% accuracy in predicting the KH-P value. In other words, this model, for the
first time, has related the KH-P value to grain boundary surface energy,γ , shear modulus, G, and
lattice constant, a0, via
0 K β G(2a γ ) H P = − .
Abstract: Microstructural evolution in pure copper during multi-directional forging (MDF) at
temperature of 77 K was studied. Flow stress during MDF at 77 K showed a monotonical increase
at all strain. Ultra fine (sub)grains of 0.15μm in diameter were evolved, which was accompanied
by deformation twinning, at strain of Σε = 2.4. In higher strain region, Σε = 6.0, lamellar-look
structure of twins extensively appeared. The lamellar spacing was 10-100nm. For comparison,
samples were also MDFed at 300 K. The flow stress curves showed an apparent steady state flow at
above strain of Σε =2.0, which implies occurrence of dynamic recovery. The evolved (sub)grain
size was 0.3 μm at high strain of Σε = 6.0. Therefore, grain refinement seems to take place more
easily by MDF at 77 K compared with that at 300 K due to effect of deformation twin.
Microstructures evolved under MDF at 77 K and 300 K showed different annealing behavior. Static
recrystallization started earlier and faster in the samples MDFed at 77K than those MDFed at 300K.
Abstract: Forming of metallic parts by the application of high intensity transitory magnetic pulses
or shock waves is a challenge task from industrial perspectives as this offers extended scope of
forming highly precise parts that result from material behavior at high deformation rates.
Electromagnetic forming requires that the part must be intrinsically very conducting. The electrohydraulic
forming is exempt from this material constraint as the deformation is generated by a shock
wave in a fluid through electric discharge in between the electrodes. The application of a static
pressure during forming is used to reduce the discharge energy for a given deformation. Work has
been conducted to form different parts through these two techniques involving aluminum, copper
and steels. The paper presents the technical obstacles still facing the electromagnetic techniques and
gives examples of formed parts and joints in relation with microstructures.
Abstract: It was limited to 60/40 brass and the adjustment of grain size was performed, thereafter, it
was processed by one way torsion working and back-torsion working. The effect of both workings
on the work hardening and the surface roughness of 60/40 brass were investigated. The quenched
material has excellent surface roughness in comparison with the furnace-cooled material both after
and before workings. It seemed that a little difference in their grain size (15-55μm) affects the
restoration ratio of surface roughness. For the back-torsion worked material, as the grain size is
coarse, the amount of hardening increases. If the β phase ratio is more, it is easy to become
hardened. Inversely, if the β phase ratio is less, it obtains the maximum amount of hardening.
Abstract: The α-phase in 60/40 brass added Si was investigated by transmission electron microscope (TEM)
in order to understand the relationship between the ability of hardening during annealing and phase
decomposition. The ability of hardening ( Δ HV), which is the value of difference between the
maximum hardness during annealing and the value of as-quenched sample, was obtained
measurement from the alloy. As a result, the Si-bearing alloy is higher in ΔHV than a base alloy
without Si. The α-phase in the Si-bearing alloy showed fringes in its TEM image like as stacking
faults, and extra reflected spots in its selected area diffraction pattern (SADP), which is
corresponding to the 9R structure. Streaks were also observed together with spots in its SADP.
Extra reflected spots and streaks in SADP became weak or disappeared when the annealing time
increased. After 600 ks annealing, SADP obtained from the α-phase could be indexed as FCC lattice.
Change in chemical composition of α-phase was also measured by the energy dispersive X-ray
Abstract: The microstructure simulation of spinodal decomposition was carried out in the isothermally-aged
Cu-Ni and Cu-Ni-Fe and Cu-Ni-Cr alloys using the phase field method. The numerical simulation
was based on a solution of the Cahn-Hilliard partial differential equation by the finite difference
method. The calculated results were compared to those determined by atom-probe field ion
microscope analyses of the solution treated and aged alloys. Both the numerically simulated and
experimental results showed a good agreement for the concentration profiles and microstructure in
the aged Cu-Ni, Cu-Ni-Fe and Cu-Ni-Cr alloys. A very slow growth kinetics of phase
decomposition was observed to occur in the aged Cu-Ni alloys. The morphology of decomposed
phases consists of an irregular shape with no preferential alignment in any crystallographic
direction at the early stages of aging in all the aged alloys. In the case of the aged Cu-Ni-Fe alloy,
a further aging caused the change of initial morphology to an equiaxial shape of the decomposed
Ni-rich phase aligned in the elastically-softest crystallographic direction <100> of Cu-rich matrix.
The growth kinetics rates of phase decomposition in Cu-Ni-Fe and Cu-Ni-Cr alloys are
appreciably faster than that in Cu-Ni alloys.