Abstract: A compressive torsion processing (CTP) was applied to hypereutectic Al-Si alloy in
order to raise ductility and formability by microstructure refinement of the alloy. The CTP is a
unique severe plastic deformation process and it can easily apply large strain to a work piece
without change in shape. In the present work, influence of compressive torsion processing
temperature on microstructure refinement and tensile property of hypereutectic Al-Si alloy is dealt
with. When the CTP was applied on the Al-Si alloy, primary and eutectic Si particles were refined
more effectively at lower processing temperature. Total tensile elongation of CTPed alloy was four
times as large as that of non CTPed one. Distribution of the total elongation was quite uniform in
the whole CTPed specimen.
Abstract: Influences of Gd or Y addition on microstructures and tensile properties at room and elevated
temperatures were investigated for T6-treated Mg-3%Nd-0.5%Zn-0.4%Zr casting alloys, on the basis of
experimental results from X-ray diffractometry, scanning electron microscopy, transmission electron
microscopy, energy dispersive spectroscopy, tensile and creep tests. Microstructures of the T6-treated
alloys are characterized by recrystallized α-(Mg) grains containing various nano-sized precipitates such
as Mg41Nd5, Zn2Zr3 and Zr particles. In T6 condition, most of added Gd and Y elements are dissolved
in Mg41Nd5 precipitates rather than formation of new phases. Tensile properties and creep resistance
of the Mg-3%Nd-0.5%Zn-0.4%Zr alloy are remarkably increased by the addition of Gd or Y, but their
efficiencies are substantially the same.
Abstract: The effect of Ca and Sr content on the microstructure and mechanical properties of a cast AZ91
magnesium alloy is investigated. Ca and Sr additions in AZ91 magnesium alloy are expected high
creep resistance. The microstructure of the alloy exhibits the dendritic α-matrix and the
second-phases forming networks on the grain boundary. Tensile tests at elevated temperatures
between 448 and 523K reveal that the creep resistance was improved with increasing the additional
amount of Ca, especially more than 1.0wt%. From the perspective of grain refinement effect, it is
expected that the additions of Ca and Sr to AZ91 magnesium alloy not only improve creep
resistance but also improve mechanical properties at room temperature.
Abstract: Twin roll casting process combines casting and hot rolling into a single process. In this study,
mechanical properties at room temperature and microstructure of the twin roll cast AZ91
magnesium alloy are investigated. The alloy exhibited a good combination of high ultimate strength
of 343MPa, yield stress of 224MPa and elongation to failure of 13%. The mechanical property was
very excellent compared with AZ91 die-cast alloy. EPMA analysis reveals that the Al concentration
in Mg matrix is higher in twin roll cast alloy than that in die-cast alloy. This high Al concentration
must be the origin of the good mechanical properties of twin roll cast alloy at room temperature.
Abstract: The influence of initial texture on the formation of primary twin system of AZ31
Magnesium rolled plate was investigated in this work. Uniaxial compression tests were carried out
on samples cut along the rolling direction (RD) and normal direction (ND) of rolled AZ31 Mg plate
at various temperatures (RT, 150, 200, 250, 300, 350, 400, 450°C) with the fixed strain rate
(0.01s-1). The results showed that the primary twinning system of AZ31 Mg alloy (c-axis extension
twin) occurred actively in the RD compression specimens, which promoted homogeneous
deformation as compared to the ND compression specimens. The effect of temperature on the
formation of deformation twins was also investigated, and slip/twin transition temperature was
found to be 250°C.
Abstract: The as-cast microstructure of Mg-5Al-3Ca-2Sm alloy consists of equiaxed α-Mg matrix,
(Mg, Al)2Ca eutectic phase and Al-Sm rich intermetallic compounds. This eutectic phase of the
extruded alloys was elongated to extrusion direction and size of this phase was finered compare to
that of as-cast alloys because of severe deformation during hot extrusion. After hot extrusion, the
average grain size of Mg-5Al-3Ca and Mg-5Al-3Ca-2Sm alloys was 4.8 *m and 3.8 *m, respectively.
In load-unload hardness test, penetration depth was decreased with added Sm and after extrusion
procedure because of grain size refining by addition Sm and large deformation. Hardness value of the
alloys containing Sm was higher than that of Mg-5Al-3Ca alloy due to grain refining and formation
Al-Sm rich intermetallic compound at gain boundary and α-Mg matrix. Maximum hardness value
was obtained at the extruded Mg-5Al-3Ca-2Sm alloy at elevated temperatures.
Abstract: The age hardening precipitates of Mg-4.7mass%Zn alloy aged at 423K,473K were studied by using
high-resolution transmission electron microscope (HRTEM).
Contrasts of mono layers were confirmed to exist on the (0001) and (1100) matrix planes. It was
considered that the contrast of mono layer was plate-like shape, and identified as pre-precipitates
from as-quenched stage to early stage of aging at 473K for 32h .
In the peak aged specimen of aged at 473K, the β1’ phase was observed. The β1’ phase has a
rod-like shape and parallel to c-axis of Mg matrix. It can be observed orientation relationship
between Mg matrix and β1’phase has not only same parts to previous reports but also different parts
in one β1’ phase .
Abstract: Interest in the rheology forming technology for fabrication of light weight materials and for
resolving environmental issues has been growing in industrial and academic society. In this study,
the helical shape stirrer was designed to produce rheological material. The experimental variables,
which were stirring time 0-1200 sec, stirring velocity 0-100 rpm and melt temperatures for semisolid
states, were established. The rheological materials were produced under established
experiment conditions, and then mechanical properties were measured. Sequence-production
equipments were appended to fabrication system of rheology material to make rheology materials
continuously. Therefore, the development of sequence-production system equipped with a specially
designed mechanical stirrer in spiral shape was necessary for fabricating fine grains and their
uniform globular rheology materials. The thixoforging was experimented with rheological A6061
wrought aluminum alloy fabricated by the spiral shape stirrer. Microstructural morphology of the
forged samples was investigated and their mechanical properties characterized.
Abstract: microstructures, aging hardness, mechanical properties of Mg-9Gd-4Y-0.3Zr alloys
were investigated. The microstructure is a typical dendritic structure of as-cast sample, The
aging test of extruded samples were carried at a temperature rang of 200-300°C and at a
different aging time. The aging peak hardness is about 120HV, tensile strength was tested at
temperature 25°C, 200°C, 250°C and 300°C, tensile strengths are 375 Mpa, 364 Mpa, 329
Mpa, 286 Mpa respectively, the maximum elongation is 13.32% at 300°C. The fracture mode
is mainly microvoid coalescence fracture combination the brittle cleavage fracture at room
temperature, and microvoid coalescence fracture at 200-300°C.
Abstract: Manufacturing technology of bulk titanium by milling and sintering was studied for
recycling of pure titanium tuning chip. Ti chips were milled at RT under H2 pressure of 0.5MPa. All
titanium chips were pulverized and hydrided within several minutes, which is very short time
comparing to other thermal processes. The hydrided powders were hot pressed at 750°C. After hot
pressing, bulk sample was identified to α-phase Ti by XRD measurement and measured
density(4.509g/cm3) was very close to theoretical density(4.512g/cm3) of pure Ti. Consequently, it is
carefully suggested that hydriding and sintering process is efficient and practicable solution for
recycling of pure titanium tuning chip.