Yutao Zhao

Physical Properties and Regulating Mechanism of Fluoride-Free and Harmless B2O3-Containing Mould Flux

The flux agents in common mould fluxes were fluoride and sodium oxide, which would do great harm to environments. B2 O3 was selected as flux. The physical properties of B2 O3-containing mould fluxes were studied. The corresponding physical properties of 37. 91 % CaO-43. 09 % SiO2-5 % Al2 O3-5 % Mg@2 % Li2 0-7 % B2 O3 mould fluxes were as follows: the melting point was 909 °C, the flowing temperature was 1 160 °C, the viscosity and surface tension at 1 300 °C were 0. 4 Pa · s and 0. 32 N/m respectively, which could meet the demands for certain kinds of steels for mould fluxes in continuous casting.

Microstructure and mechanical properties of AZ91 magnesium alloy subject to deep cryogenic treatments

AZ91 magnesium alloy was subjected to a deep cryogenic treatment. X-ray diffraction (XRD), scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM) methods were utilized to characterize the composition and microstructure of the treated samples. The results show that after two cryogenic treatments, the quantity of the precipitate hardening β phase increases, and the sizes of the precipitates are refined from 8–10 μm to 2–4 μm. This is expected to be due to the decreased solubility of aluminum in the matrix at low temperature and the significant plastic deformation owing to internal differences in thermal contraction between phases and grains. The polycrystalline matrix is also noticeably refined, with the sizes of the subsequent nanocrystalline grains in the range of 50–100 nm. High density dislocations are observed to pile up at the grain boundaries, inducing the dynamic recrystallization of the microstructure, leading to the generation of a nanocrystalline grain structure. After two deep cryogenic treatments, the tensile strength and elongation are found to be substantially increased, rising from 243 MPa and 4.4% of as-cast state to 299 MPa and 5.1%.

In-situ fabrication of particulate reinforced aluminum matrix composites under high-frequency pulsed electromagnetic field

Abstract Pulsed magnetic field is generated when imposing pulse signal on high-frequency magnetic field. Distribution of the inner magnetic intensity in induction coils tends to be uniform. Furthermore oscillation and disturbance phenomena appear in the melt. In-situ Al 2 O 3 and Al 3 Zr particulate reinforced aluminum matrix composites have been synthesized by direct melt reaction using Al-Zr(CO 3 ) 2 components under a foreign field. The size of reinforced particulates is 2–3 μm. They are well distributed in the matrix. Thermodynamic and kinetic analysis show that high-frequency pulsed magnetic field accelerates heat and mass transfer processes and improves the kinetic condition of in-situ fabrication.

Preparation and tensile properties of DD5 single crystal castings

The preparation procedure of DD5 single crystal castings was optimized. The microstructure characteristics of DD5 single crystal superalloy were investigated by microstructure observation and segregation behavior examination. The results show that the grain orientation is optimized by constraining the spiral crystallizer in [001] orientation and spatial scale. Also, the γ’ phase of inter-dendrites is larger and more irregular than that in dendrite arms. High temperature tensile tests of DD5 single crystal castings exhibit that the peak stress increases with increasing temperature, while the area reduction shows an opposite trend, when the temperature is below 800°C; meanwhile, when the temperature is between 800°C and 1000°C, the fracture stress of the alloy is the same as the peak stress. The fracture mode changes from shear to ductile with increasing temperature from 600°C and 1000°C.

Effects of B2O3 and CaF2 on Melting Temperatures of CaO-SiO2-Fe2O3 System Fluxes

Fluorite is widely employed as fluxing agent in metallurgy flux, which inevitably leads to serious fluorine pollution. B2O3 is employed as fluxing agent of CaO-SiO2-Fe2O3 steelmaking fluxes to substitute for CaF2. The effects of B2O3 and CaF2 on the melting properties of this system were investigated. The melting temperatures of fluxes including softening temperature (Ts), hemispherical temperature (Th), and flow temperature (Tf) were measured using the hemisphere method. The results indicate that the fluxing effect of B2O3 is more significant than that of CaF2. When the addition amount of B2O3 (mass percent) exceeds 6%, the melting temperatures of fluxes including Ts, Th and Tf are decreased lower than 1 300 °C. The basicity of fluxes has a significant effect on the melting temperature, and the melting temperatures of the fluxes increase with the increase of fluxes basicity. However, when B2O3 is used as fluxing agent, the melting temperature changes little with the basicity increasing from 2.5 to 5.0. These characteristics are suitable for steelmaking process. Moreover, Fe2O3 has an important fluxing effect on this CaO-based steelmaking fluxes. This indicates that the fluxes system is suitable for steelmaking process.

Study on the preparation and microstructure of a single-crystal hollow turbine blade

ABSTRACT This paper studied the structural design of a ceramic core and a blade, ceramic core localization, shell preparation, casting process, core leaching technology, and the heat treatment process of a single-crystal hollow turbine blade. The results show that the single-crystal structure solidification sequence of the blade platform is consistent with the cooling sequence and the pulling-out direction of the blade. The primary dendrites were obviously enlarged with the increase of the blade thickness owing to the change in the local cooling rate. Besides, the γ′ phase had a high uniform size distribution ranging from 0.40 to 0.60u2009µm after heat treatment, and the cubic degree was more homogeneous in comparison with the as-cast microstructure, which are favorable for the superalloy structure. Moreover, γ′ phase size gradually increased and its quantity gradually reduced owing to the increase of the wall thickness in the growth direction.

Study on Composite Modified Ceramic Shell of Mineralizer and Short-Cut Carbon Fiber

This experiment by using the composite method of the Mineralizer and short-cut carbon fiber to improve the performance of the shell, The influence of addition of mineralizer and the addition and length of short-cut carbon fiber on the high-temperature strength and high-temperature gravitational distortion of ceramic shell was investigated by orthogonal experiment.The results showed that the composite modified fused corundum shell is 11.33MPa higher than the normal fused corundum shell of 4.43MPa, and the high temperature gravitational distortion is reduced from 1.25% to 0.38%. Therefore, ceramic shell with excellent properties can be prepared by adjusting the addition of mineralizer, the addition and the length of short-cut carbon fiber. Introduction With performance of the aerospace and industrial gas turbine blade continuing to improve, the hollow single crystal blade has been developed at home and abroad [1]. The successful preparation of the blades is based on the following characteristics: (1) Sufficient ambient temperature strength(green strength) to withstand dewaxing without failure; (2) Enough high temperature strength to withstand the static pressure of molten metal; (3) In order to improve the surface finish, the shell wall must not react chemically with the molten metal, so high chemical stability is indispensable; (4) High temperature creep resistance to ensure accuracy of shape and size of the casting; (5) Favorable permeability and thermal conductivity be aimed to improve the rate of single crystal formation.Especially[2,3,4]. Therefore, the research of the mechanical properties of ceramic shell has practical productive significance. At present, the researches for shell of the fused corundum silica sol binder, the domestic research scholars mainly have been adding mineralizer to the slurry to improve shell performance, Such as 811-type shell of mineralizer[5,6]. Ceramic shell be modified by P.M.Curran et al.who used CaO to obtain a new shell with high strength and favorable creep resistance[7]. However, the single crystal blade, with the more complex structure and the increasing size, results in that the shell is easy to be cracked due to the insufficient green strength during the process of preparation. In particular, the thickness of the sharp edge of the shell is reduced by 2 to 3 mm compared to the large plane, as a results, leading to the emergence of cracks and bleed-out in the directional solidification of casting[8]. Meanwhile,with the pouring temperature of the high temperature alloy continuing to increase, so non-deform ability of shell reduced that size of casting cannot be guaranteed.Lv kai et al.who added glass fiber into slurry system, the results showed that with the amount increasing of glass fiber, the bending strength of the shell increased significantly,and the high temperature gravitational distortion first increased and then decreased[9].S. Jones et al. have studied polymer modified shell and nylon fiber shell, both of which effectively improved the smoothness of the inner surface of the shell and reduced the shell thickness. The bending strength of the polymer modified shell was obviously improved than nylon fiber shell[10]. The shell was prepared by US Howmet Co.,Ltd.who used continuous carbon fiber without bleed-out and waved surface, chord width of the blade without elongation and the bow of blade without displacement[11]. According to the above investigations, the ceramic shell is studied by combining high tensile Proceedings of the 3rd International Conference on Material Engineering and Application (ICMEA 2016) Copyright