Abstract: Changes in microstructure and damping capacity with aging time for solutionized AZ91
(Mg-9%Al-1%Zn-0.2%Mn) alloy have been investigated based on experimental results from optical
micrography, X-ray diffractometry, hardness test and damping capacity measurement vibrating in a
flexural mode. Discontinuous β (Mg17Al12) precipitates form along the primary grain boundaries, the
amount of which increases as the aging time increases. The hardness of α matrix with respect to aging
shows a typical “S” shape, indicating a generation of fine continuous precipitation in the matrix during
aging. The peak level of damping capacity for the AZ91 alloy is obtained after 1 hour of aging, over
which the damping capacity becomes deteriorated continuously. The optimum density of continuous
β precipitates with fine morphology, which may well act as pinning points for dislocation lines, might
be responsible for the improvement of damping capacity.
Abstract: Free-cutting phosphor bronze alloy (ASTM C54400) was used as a material for automotive
parts and industrial valve parts for its high strength, machinability and excellent corrosion resistance.
To obtain desired mechanical strength of the alloy, the process parameters including continuous
casting speed, reduction in area and annealing temperature have to be controlled. In this study, we
investigated the effect of annealing on the mechanical property and machinability of free-cutting
phosphor bronze alloy fabricated by continuous casting with different casting speeds of 80, 100, and
120 m/min, respectively. After annealing, the tensile strength of the alloy decreased with increasing
annealing time owing to the occurrence of recrystallization and grain growth. In the cast and swaged
alloy produced at casting speed of 120 m/min, the grain growth occurred rapidly. In contrast, in the
alloy produced at the casting speed of 80 m/min, the grains growth rate was low. Furthermore, the
effect of Pb particle in the alloy on machinability was also investigated by using a tool dynamometer
installed force sensor.
Abstract: A practical and important idea regarding solid state recycling of magnesium alloys is explored.
Chips of AZ91D have been put in hot air environment for accelerated oxidation to simulate the
to-be-recycled state of Mg alloy scraps. These chips materials received extrusion process and
subsequent annealing treatment. Tensile tests showed that the extruded plate had higher strength than
that of ordinary die cast counterpart. Micro-structure investigation indicated it was probably due to
finer grains of the Mg matrix as a result of extrusion. Further annealing did not seem to alter this fine
structure, yet it could diminish some un-favored form of Mg17Al12 compound. Thus, post-annealed
solid state recycled AZ91D showed impressive strengths and elongations.
Abstract: Three types of L12-type Al3Ti-Cr alloys, of compositions 67Al-25Ti-8Cr, 66Al-24Ti-
10Cr, and 59Al-26Ti-15Cr in atomic percent, were corrosion tested at 900, 1000, and 1100oC in an
Ar-1% SO2 gas atmosphere for up to 150 h. The alloys were resistant to corrosion because a thin
Al2O3 barrier layer was formed on the alloy surface due to the high Al content in the alloys. Due to
the very strong Al affinity for oxygen, virtually no sulfur was detected inside the oxide scale.
Abstract: In the continuity casting technology of steel-manufacturing process, the tundish has two
important functions: the preservation and distribution of molten metal and the reaction container
able to perform float-out separation of nonmetallic inclusions. The residence time affects the
effective removal of the nonmetallic inclusions. In this study, a T-shaped tundish with a submerged
entry nozzle (SEN) and three strands was investigated for its ability to extend the residence time.
Analysis conditions were the shape of the dam which was transformed to three cases. Fluid flow
and non-metallic inclusion movement were also analyzed. The movement and removal of nonmetallic
inclusions was determined by residence time distribution (RTD) analysis. As a result, the
number of float-out, non-metallic inclusions was increased when the deviation of mean residence
time was reduced.
Abstract: In the present study, the influences of load on the abrasive wear properties of
silica-filled epoxy resin composites were investigated at ambient temperature. The friction
coefficient, wear rate and specific wear rate against SiC abrasive paper were determined
experimentally. The sliding wear tests of the materials demonstrated that the friction coefficient and
the wear rate of silica filled epoxy composites were lower than those of the pure epoxy. The
cumulative wear volume tended to increase nonlinearly with increase of sliding distance and
depended on diameter of the silica particle for all these composites. The friction coefficient and
wear rate were raised substantially with an increase in applied load.
Abstract: Driven largely by the never ending quest for weight reduction to decrease fuel consumption
and emission, the automotive industry is predicting significant growth in the use of aluminum alloys.
Generally, cold chamber type die casting process is utilized for aluminum alloys. In order to comply
with the growing demand for life cycle environmental effect, life cycle assessment (LCA) was carried
out for producing A356 aluminum alloy by cold chamber type die casting process, based on what has
been experienced as needed for LCA study. The main emphasis of this study is to evlauate the effect
of trial of improving die casting process and product quality on the environmental value obtained by
LCA. Also the results will be compared by the trial of life cycle improvement. In LCA, the process
evaluated was based on yields of finished parts relative to the metal input. This is important both in
environmental point of view and in commercial point of view, because the environmental data are
sensitive to the design of the cast part and the efficiency of the die casting operation.
Abstract: In the paper, the Sn2.5Ag0.7Cu solder alloy is selected out by comprehensive comparison.
Minute a mount of rare earth (RE) was added into Sn2.5Ag0.7Cu solder aiming at examining the
effect of different a mount of RE on microstructure,the physical properties and mechanical
properties of Sn2.5Ag0.7Cu solder.the aim is to define the optimization range of the RE addition.
Abstract: In this study, the mechanical properties of silica-filled epoxy resin composites with
average silica particle diameter of 6-33m were investigated at ambient temperature and pin-ondisc
friction test was conducted for this. Experimental results demonstrated that mechanical
properties such as flexural strength, flexural modulus and critical stress intensity factor depend on
average particle diameter. The flexural strength decrease with increase of particle size whereas the
critical stress intensity factor increases with increases of particle size. Wear rates of silica-filled
composites are below a half those of unfilled epoxy. Fracture surface analysis was discussed based
on SEM examination.
Abstract: This work describes the effect of microstructures on elastic modulus in Ti-26Nb-xSi alloy
(x=0.5~1.5at.%) prepared by arc melting, cold rolling and recrystallization heat treatment. OM
observation and x-ray diffraction analysis revealed that the microstructure of as-quenched sample
appeared to mixture appearance consisting of mostly bcc-structured β phase and small amount of
orthorhombic-structured α″ phase. After cold rolling, elongated structure parallel to the rolling
direction was observed, and equiaxed structure with the average grain size of about 20~30μm was
developed for the sample after recrystallization heat treatment. In as-quenched sample randomly
distributed feature of pole figure was characterized without showing a specific texture component. In
cold-rolled sample α-fiber, γ-fiber and rotated cube texture components were detected. After
recrystallization heat treatment the intensity of α-fiber texture component was markedly decreased,
while the rotated cube component becomes sharpened and γ-fiber component remains relatively
unchanged. The elastic modulus increased by cold rolling and then decreased by recrystallization over
the entire chemical composition range investigated. The variation of elastic modulus values was
interpreted in terms of changes in texture components depending on thermomechanical processing.