Foundry at Shenyang University of Technology

The discipline of foundry at Shenyang University of Technology (SUT) was founded in 1952, and began to enroll postgraduate students in 1979. And in 1981, the discipline was qualified to confer master's degree, which was one of the first majors who had the right in China. And in 1984, she was granted as the key discipline by the former Chinese Ministry of Machinery Industry. In 1998, according to the new Catalogue for Undergraduate Specialties issued by the Ministry of Education, the discipline of foundry was adjusted to be involved by the new generalized discipline of Materials Processing Engineering. The new discipline was granted as one of the key disciplines of Liaoning province, and was qualified to have the right of conferring doctor's degree the same year. The discipline of foundry at SUT has a very strong staff of teaching and scientific research. At present, there are 23 staff members, including 1 academician (dual employment), 5 doctoral supervisors, 10 professors, 4 associate professors, 3 lecturers, 1 senior research engineer, 2     

Precipitation mechanism of an MoNi type intermetallic phase in W–27.0at.%Mo–35.6at.%Ni–17.6at.%Fe

For W–27.0Mo–35.6Ni–17.6Fe (at.%) sintered at 1500 °C for 240 min, an MoNi type intermetallic phase was formed during cooling, when either a water-quenching or furnace-cooling practice was employed. For the water-quenched specimen, a quasi-eutectic reaction took place, wherein the intermetallic phase precipitated directly from a eutectic liquid phase, which was super-saturated with W and Mo, in the form of a lamellar structure along with the Ni-based matrix phase. Accordingly, the intermetallic phase was located primarily in the interstices between the grains of the Ni-based matrix phase. On the other hand, for the furnace-cooled specimen, the intermetallic phase was formed by the peritectoid reaction between the Ni-based matrix phase and the W–Mo grains. The intermetallic phase thus existed primarily at the boundaries between the Ni-based matrix phase and the W–Mo grains.     

Superconducting Magnetic Flux Transformer at 77K

Superconducting Quantum InterferenceDevice(SQUID)magnetometer is a kind ofmagnetic flux sensor with high sensitivity,andtherefore can be used in geological prospectand biomagnetic field etc..But the SQUIDmagnetometer used before has to be used atthe temperature of 4.2K provided by liquidhelium and thus its application is limited.Since     

Plasma-nitriding of tantalum at relatively low temperature

The combined quadratic orthogonal regression method of experiment design was employed to explore the effectsof process parameters of plasma nitriding of tantalum such as total pressure, temperature and original hydrogen molar frac-tion on the hardness, roughness and structure of nitriding surfaces. The regression equations of hardness, roughness andstructure were given according to the results of regression and statistic analysis. And the diffusion activation energy of ni-trogen in tantalum on plasma nitriding conditions was calculated according to the experimental data of hardness ofplasma-nitriding of tantalum vs time and temperature. The diffusion activation energy calculated belongs to (155.49±10.51)kJ/mol(783-983K).     

Deformation behavior of dispersion-strengthened copper at high temperature

1. Introduction Dispersion-strengthened copper (DSC) is a promising material developed recently. Considerable attention has been focused on it because of its excel- lent high-temperature properties. The metallic mate- rial, which is strengthened by solution strengthening, deformation strengthening, and ageing strengthening, is always low at high temperature, and the strength- ening factor contradicts with the electrical conduc- tivity of the material to a certain extent [1-2]. But DSC has g…     

Isothermal section at 927℃ of Cr-Ni-Ti system

The isothermal section at 927℃ of the Cr-Ni-Ti system was established using a high-efficiency diffusion couple approach, supplemented with eight equilibrated alloys. The alloy compositions were selected on the basis of the experimental results from the diffusion couple. Both the diffusion couple specimens and the alloys were examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. No ternary compound is found at 927℃. The following five three-phase equilibria are well determined： TiNi3＋（Cr）＋（Ni）, TiNia＋（Cr）＋TiNi, TiNi＋（Cr）＋Cr2Ti, Ti2Ni＋Cr2Ti＋TiNi and Ti2Ni＋Cr2Ti＋（Ti）. The solubilities of Cr in NiTi2, NiTi, and Ni3Ti are determined to be 7.5%, 14.5% and 11.4% （molar percent）, respectively, α-Cr2Ti and β-Cr2Ti dissolve about 9.2% and 13.9% Ni （molar percent）, respectively.     

Internal friction in γ-TiAl at high temperatures

The internal friction in TiAl polycrystals of technical purity was studied in the temperature range of 300–1500 K using an inverted torsion pendulum. Extruded single-phase γ-TiAl with an aluminium content of 54.1 at.% shows a large, frequency-dependent relaxation maximum near 1300 K during cooling from temperatures above 1400 K, which is neither observed during heating from ambient temperature nor in two-phase α₂/γ-TiAl alloys with a lower Al content. This relaxation maximum is tentatively ascribed to the motion of grain boundaries or dislocations, which are pinned by precipitates in γ-TiAl. The precipitates dissolve at temperatures above 1350 K and form again below 1200 K. No relaxation is observed in polycrystalline TiAl with a carbon content in the range from 0.009 to 0.22 at.% at temperatures below 900 K. This behaviour may be an indication of hardening by finely dispersed precipitates, as observed in TEM and SEM micrographs.     

Creep- and coarsening properties of Al–0.06 at.% Sc–0.06 at.% Ti at 300–450 °C

Upon aging at 300–450 °C, nanosize, coherent Al₃(Sc_1−xTi_x) precipitates are formed in pure aluminum micro-alloyed with 0.06 at.% Sc and 0.06 at.% Ti. The outstanding coarsening resistance of these precipitates at these elevated temperatures (61–77% of the melting temperature of aluminum) is explained by the significantly smaller diffusivity of Ti in Al when compared to that of Sc in Al. Furthermore, this coarse-grained alloy exhibits good compressive creep resistance for a castable, heat-treatable aluminum alloy: the creep threshold stress varies from 17 MPa at 300 °C to 7 MPa at 425 °C, as expected if the climb bypass by dislocations of the mismatching precipitates is hindered by their elastic stress fields.     

Preparation of aluminide coatings at relatively low temperatures

1 Introduction Protective coatings by pack aluminizing are frequently applied to metals to protect them from high temperature oxidation and hot corrosion attack [1, 2]. Pack aluminizing consists of heating the parts to be coated in a closed or vented pac…     

Tribological behavior of Ni-Cr-based composite at high temperatures

The wear behavior of Ni-Cr-based alloys was investigated at ambient and elevated temperatures. The wear samples were prepared by metallurgical hot pressing. Wear tests were carded out on a general purpose wear testing machine having a heating unit and pin-disc sample configuration. The counterface material was prepared from Al2O3 ceramics. The tests were carded out at room temperature （RT）, 200 ℃ and 600℃. The effects of temperatures on the tribological properties were determined by using optical microscopy, and X-ray diffractometry. The results show that at room temperature the worn surfaces of the alloys are characterized by mild scuffing and micro cracks, the action of nano-crystal structural wear debris on the worn surfaces is responsible for the reduction of friction. At 200℃, the friction coefficient is the highest. The worn surfaces of the alloys are adhesive and oxidative. At 600℃, the friction coefficient is reduced due to the effect of the oxides, tungstates and sulfides residue on the worn surface.     

Ion exchange at a metal–ceramic interface

We present the results for an interfacial reaction between magnesium aluminate spinel and aluminum metal at 640 °C which, for the first time, show the occurence of ion exchange at a metal–ceramic interface. The exchange reaction occurs by the diffusion of magnesium and aluminum ions across the interface in opposite directions. The enrichment of the spinel in aluminum cations, and the metal in magnesium is confirmed by the appearance of phases of aluminum oxide and magnesium–aluminum intermetallics in the X-ray diffraction spectra. Electron spectroscopic images of spatial elemental distribution provide further evidence for the reaction. A drop in the thermal and electronic conductivities are explained by enhanced scattering of the electrons by solid solution Mg in the aluminum metal. The experiments were carried out on composites consisting of an aluminum matrix with a fine dispersion of spinel particles, whose size was varied while the volume fraction was held constant. Measurable ion exchange reaction was seen only in the composites containing the smaller (one micrometer size) particles. The influence of surface to volume ratio of the particles on the reaction rate confirms that the reaction was interface controlled. The possibility of a nucleation and growth process for the conversion of spinel into alumina and solid solution magnesium was ruled out by quantitative thermodynamic analysis.     

Stress corrosion cracking at constant load of 304L stainless steel in molten NaCl-CaCl2 at 570°C

The incubation and propagation times of cracks in 304L in molten NaCl-CaCl₂ at 570°C were related to the applied stress value, from creep and creep rate curves. Rest potential versus time curves were recorded simultaneously. The results showed intergranular stress corrosion cracking. When the temperature was kept at 570°C, precipitation of chromium carbide M₂₃C₆ which promoted cracking propagation, was induced. Determination of the crack rate shows that anodic dissolution at the bottom of the cracks is the main process during the stress corrosion crack propagation of 304L stainless steel in the stress range used.     

Oxidation behaviour of Fe–40 at.-% Al intermetallics with Li or Cu additions at high temperature

Fe–40?at.-% Al intermetallics with the addition of Li (1 and 3?at.-%) and Cu (3 and 5?at.-%) were produced using standard casting techniques. The oxidation behaviour was obtained using thermogravimetric analyses in an atmosphere of 99.99% oxygen at 800, 900, 1000, and 1100°C. The oxidation product layers on the top and cross-sectional views were characterised using SEM and energy-dispersive X-ray spectroscopy mapping. The different alumina phases can produce a double layer with different mechanical and chemical properties. The results showed that the addition of 1% Li assisted the activation of the oxide production at 1000 and 1100°C, while the rest of the third element additions slightly modified the oxidation resistance.     

The Gd-Al-Si Isothermal Section at 500 °C

Phase relations in the Gd-Al-Si system have been established and experimentally studied at 500 °C. The system has been experimentally investigated by mean of scanning electron microscopy (SEM), electron microprobe analysis (EDXS) and x-ray powder diffraction (XRPD). The existence of four ternary compounds has been confirmed: τ₁ GdAl₂Si₂ (hP5-CaAl₂Si₂ type), τ₂ GdAlSi (tI12-αThSi₂ type), τ₃ Gd₄AlSi₃ (oC8-CrB type) and τ₄ Gd₆Al₃Si (tI80-Tb₆Al₃Si type). Three ternary compounds show a composition homogeneity range: τ₂ dissolves Si up to about 37 at.%, τ₃ shows an homogeneity range (towards the GdSi compound) to 45 at.% Si concentration value, finally the τ₄ phase dissolves 5 at.% of Si. All binary compounds dissolve the third element, except for GdAl The ternary system is characterized by 16 three-phase fields, and 16 two-phase fields.     

Creep mechanism of Mg-Nd-Zn-Zr alloy at ambient temperature

Magnesium alloy＇s creep stress exponent and creep mechanism at the room temperature were analyzed by TEM. Relationship among strain, stress and creep time was studied. The creep rate of some mechanisms were calculated. The results show that the dislocation mechanism is possible. The deformation mechanism is dislocation slipping on basal plane, and twinning improves creep deformation.     

The Oxidation of Fe-2 and 5 at.% Y Alloys at 600-800°C in Air

The oxidation of Fe-Y alloys containing 2 and 5at.% Y and pure iron has been studied at 600-800°Cin air. The oxidation of pure iron follows the parabolicrate law at all temperatures. The oxidation of Fe-Y alloys at 600°C approximatelyfollows the parabolic rate law, but not at 700 and800°C, where the oxidation goes through severalstages with quite different rates. The oxide scales on Fe-2Y and Fe-5Y at 700 and 800°C arecomposed of external pure Fe oxides containingFe₂O₃,Fe₃O₄, and FeO, with FeO being themain oxide and an inner mixture of FeO andYFeO₃. The scales on Fe-2Y and Fe-5Y at 600°C consist ofFe₂O₃,Fe₃O₄, andY₂O₃, with a minor amount of FeO.Significant internal oxidation in both Fe-Y alloysoccurred at all temperatures. The Y-containing oxidesfollow the distribution of the original intermetalliccompound phase in the alloys. The effects of Y on theoxidation of pure Fe are discussed.