Guangxin Wu

Grain Refinement Behavior of Al‐Zn‐Si Alloy by Inoculation in Hot‐Dip Coating

Grain refinements were an effective method to improve the mechanical properties of aluminium alloy, and heterogeneous nucleation was widely applied in industry to achieve a grain-refined. In this study, grain refinement behavior of 55%Al-Zn-1.6%Si alloy by Al-Ti-B was investigated. In order to obtain the microstructure in situ, high-temperature liquid quenching by stainless steel pipe was used to capture the sample snapshots. Then, the effect of Al-5Ti-0.2B on the alloy was analyzed by microstructure, solid fraction and grain size. Our results show that the grain size of 55Al-Zn-Si alloy decreased after the Al-5Ti-0.2B addition to some extent, and in order to understand the effect of refinement, it was necessary to analyze the mechanisms of Ti in 55Al-Zn-Si alloy. Meanwhile, during the process of solidification, the solid fraction of 55Al-Zn-Si alloy was further increased with the temperature decreasing, and the result was consistent with our calculation of phase diagram. Finally the reactions were identified using calculation of phase diagram.

Microstructure simulation of rapidly solidified ASP30 high-speed steel particles by gas atomization

In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element (CAFE) model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions (UDFs) to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also investigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy (SEM). The experimental results showed that four major types of microstructures were formed: dendritic, equiaxed, mixed, and multi-droplet microstructures. The simulated results and the available experimental data are in good agreement.

First Principles Investigation on TiAl3 Alloys Substitutively Doped with Si

The site preference of Si in TiAl3 is calculated using first principles method based on Density Functional Theory. Through the analyses and comparison of the binding energy of systems with different substitution behaviors, it is shown that Si prefers to occupy the site of Al(2) and the limited solubility of Si in TiAl3 is around 12.5%. Then this article made a research on the antioxidant properties of different doped concentration of Si in TiAl3, and the result showed that the Si doping enhanced the oxidation resistance of the Ti-Al alloy.

The Investigation on the Intermetallic Layer of Hot Dipping Al‐10Si Alloy With 22MnB5 and DC51 Substrate

Hot-dipping Al-Si coating of 22MnB5 steel and DC51 steel were done in molten Al-Si bath with about 10%Si for different dipping time ranging from 3 to 300 seconds, at the temperature of 660°C, 680°C and 700°C. To study the influence of different matrix, temperature and dipping time on the intermetallic layer, the microstructure of the intermetallic layer was observed by scanning electron microscope(SEM) with energy dispersive spectroscopy(EDS). The results show that the both intermetallic layers are mainly composed of Fe2Al5 and Al9Fe2Si2.τ10-Al9Fe4Si3 was found near the boundary of Fe2Al5 and Al-Fe-Si intermetallic layer when the dipping time up to 300s. It also shows that the growth rate of interfacial layer on the 22MnB5 substrate is bigger than the intermetallic layer on DC51 steel at the same temperature (660°C, 700°C) except 680°C in a certain time range.

The Wetting Behavior of Fe-Si and Fe-Mn Alloy with Al-10%Si Coating

High-strength steel possesses excellent strength, toughness, wear resistance and weld-ability and therefore, are widely used in various fields. Because the high strength steel contains highly content of Mn and Si, they always lead to quality problem for the process of hot-dip aluminum coating. In this work, we applied improved sessile drop method, selected some characteristic systems to measure the change in contact angle and diameter of Al-10%Si droplets wetting on a quality of Mn (0wt%, 0.5 wt%, 1.5wt%, 2.5wt%) and Si (0wt%, 0.5wt%, 1.5wt% 2.5wt%). Then the microstructure and composition of interfacial layer are analyzed by SEM/EDS, the phase composition is analyzed by XRD. The results showed that the contact angle is increasing with the contents of Si increasing. However, the contact angle is decreasing with the contents of Mn increasing.

The Influence of Mn on the Interfacial Reaction for Hot-Dipping 55Al-Zn-1.6Si/Iron

The reactive diffusion layer between solid Fe-Mn and liquid 55Al-Zn-1.6Si (Galvalume, GL) was experimentally observed using Fe-Mn/GL diffusion couples. The diffusion couples were prepared by vacuum sealed technique and then immediately annealed at temperatures of T=873 K for various times up to t=2h. During annealing, a compound region consisting of Fe2Al5 and FeAl3 and T5 intermetallic compound is formed at the interface in the diffusion couple. The thickness is much smaller for the FeAl3 layer than for the Fe2Al5 and layer. Comparative study the influence of different content of alloy elements manganese on the interface reaction layer, The interfacial reaction layer thickness is getting thinner with the increase of manganese content. Through the first-principles method gives a theoretical explanation for this phenomenon.

First-Principles Study of Mechanical Property and Electronic Structure of Quenching and Aging U-Ti Alloy

We use the first principles plane wave pseudopotential method calculated the mechanical property with respect to the quenching and aging process of uranium-1.3 wt.% titanium alloy, including the elastic modulus, bulk modulus, Young’s shear modulus and the ideal tensile strength, meanwhile deeply research on the mechanical property mechanism changes through t-he electronic structure. The results show that t-he elastic modulus and ideal tensile strength of quenching state are 198GP and 21.2GP, respectively, and slightly improving through aging treatment. The variation of energy and electronic structure of uranium-titanium solid solution in process of quenching indicate the phase transition from γ phase (cubic structure) to α′ phase (orthorhombic structure) lead to improve to the mechanical property. In process of aging, at the beginning the metastable supersaturated solid solution appears Guinier-Preston (G.P) zones, which are aggregate of solute atoms in the uranium matrix, further improving the tensile strength. Then U2Ti (hexagonal structure) precipitates present in over-aged process as a result of decomposition of metastable α′ phase and reduce the tensile strength. The result shows that the G.P/matrix and precipitate/matrix interfaces have ideal work of adhesion are 15.2eV and 12.5eV, respectively. Our results demonstrate theoretically quenching and aging heat treatment strengthening effect of uranium-titanium alloy.Copyright