J.Z. Cui

Effect of combined application of electromagnetic fields on horizontal direct chill casting of 7050 aluminium alloy

Abstract Influence of combined electromagnetic field application on horizontal direct chill casting of 7050 aluminium alloy is investigated. Temperature measurement and structure observation are carried out to analyse the casting process under different electromagnetic fields. Combined electromagnetic field can reduce the harmful gravitational thermal effect in the horizontal direct chill casting process and improve the ingot properties. With application of combined electromagnetic field, temperature distribution in the melt is more uniform, sump of the ingot becomes flat and symmetric, surface quality of ingot improves markedly, grain morphology changes from feathery grains to equiaxed grains and grain size decreases. Distribution of copper and zinc in the transverse section of the ingot becomes more uniform.

Superplastic behavior of a β-forged Ti3Al–Nb alloy

Abstract Superplastic behavior of a β-forged Ti 3 Al-based alloy was investigated by compression tests and tensile tests and the microstructural evolution during the deformation process was studied. The results show that the true strain of the material reached 2.0 without surface cracking at 980°C and 2×10 −3 s −1 in a compression test, while the elongation was only about 100% at 980°C and 10 −4 s −1 . In the primary stage of superplastic deformation, the separation of lath-like O grains occurred. Newly formed equiaxed O grains slid and rotated in B2 phases and dislocation movements in B2 phase accommodated the sliding process.

Effect of low frequency electromagnetic field on as casting structure and surface quality of horizontal direct chill casting 7075 alloy

Abstract Horizontal direct chill (HDC) casting is a well established production route for aluminium alloy ingots; however, the ingots may suffer from inhomogeneous microstructures and serious macrosegregation due to the unbalanced cooling condition and gravitational effect. The present study considers the HDC casting of 7075 aluminium alloy ingot under the influence of a low frequency electromagnetic field (LFEF). Temperature measurement is employed to analyse the effect of LFEF on the HDC casting process. Surface topography and structure observation are conducted to analyse the effect of LFEF on the surface and interior quality of the HDC ingot. The results show that the LFEF can effectively uniformalise the thermal distribution, flatten the sump shape, improve the ingot surface quality, promote a transition from columnar/feathery to equiaxed dendritic growth and has a distinct grain refining effect.

Microstructures of Mg–Al binary magnesium alloy solidified with ultrasonic treatment

Abstract Phase morphology is one of the most important microstructural characteristics determining the mechanical properties and therefore, the service performance of polycrystalline materials. The effect of ultrasonic treatment on the β-phase (Mg17Al12) morphology of Mg–9·0Al alloy is studied in the present paper. The result shows that with high intensity ultrasonic vibration employed during the solidifying of Mg–9·0Al, the β-phase in the entire cross-section of the billet is significantly refined and also changed from continuous to discontinuous morphology. Spherical β-phase is formed during the solidification of billet treated with high intensity ultrasonic vibration.

Effects of low frequency electromagnetic field on solidification of 7050 aluminium alloy during hot top casting

Abstract On the basis of conventional hot top casting, low frequency electromagnetic field is applied during conventional hot top casting process. Effects of low frequency electromagnetic field on cold fold, macrostructure, microstructure and sump shape have been studied. The experimental results show that with the application of the low frequency electromagnetic filed, the as cast structure has been refined, the depth of cold fold is decreased, the upstream conduction distance becomes long, and the sump becomes shallow. The reasons for the low frequency electromagnetic field refining the structure of the ingot, making the upstream conduction distance long and the sump shallow were summarised.

EFFECT OF LOW-FREQUENCY ELECTROMAGNETIC FIELD ON THE AS-CASTING MICROSTRUCTURES AND MECHANICAL PROPERTIES OF HDC 2024 ALUMINUM ALLOY

The influences of the low frequency electromagnetic field on the horizontal direct chill casting process were investigated experimentally. Ingots of 2024 aluminum alloy with a cross size of 40 mm×200 mm were produced by the conventional horizontal chill casting process and low frequency electromagnetic horizontal chill casting process respectively. The as-cast structures and the mechanical property of the ingots were examined. The results showed that the low frequency electromagnetic field could substantially refine the microstructures and pronouncedly reduce the macrosegregation in the horizontal direct chill casting process. Moreover, the surface quality of the ingot was prominently improved by the low frequency electromagnetic field. The fracture strength and elongation percentage of the ingot was increased with the low frequency electromagnetic field.

Modeling and Experimental Research of Four-Strand Low-Frequency Electromagnetic Casting Aluminum Alloy

With the aid of ANSYS software, the effect of different mould external part materials on magnetic flux density in the aluminum melt and magnetic field interaction of four coils applied with same currents were investigated. Calculating results showed that magnetic flux density in the aluminum melt was greatly improved and the magnetic field interaction among different coils was decreased when external part of mould is made of soft magnetic material. Based on the finding, a four-strand low-frequency electromagnetic casting 6063 aluminum alloy experiment was carried out in the laboratory. The experiment showed that the surface of the billet was smooth and had no exudations and cold shuts, the as-cast microstructures were fine, uniform, equiaxed, nei-globular or globular under low-frequency electromagnetic field. The microstructure becomes finer with increased current value.

Effects of low frequency electromagnetic field on efficiency of refiner and hydrogen concentration in pure aluminium

Abstract For aluminium alloys, the sizes of the grains can be important in determining the performance in structural applications. Al–Ti–B master alloy is a good grain refiner for aluminium alloys, but the fraction of particles which nucleate grains is small. The possibility of increasing the efficiency of refiner is studied in this research. The experimental results show that the efficiency of refiner is improved by applying low frequency electromagnetic field. In addition, hydrogen concentration in the melt is reduced from 0.19 mL/100 g to 0.16 mL/100 g when the current intensity is 100 A.

Direct chill casting of magnesium alloy under pulsed magnetic field

To refine the grain size and improve the hot workability, the billets of AZ80 magnesium alloy were cast by a new process of the pulsed magnetic field-direct chill casting. The effect of pulsed magnetic field on the grain size, segregation and mechanical properties of cast billet were investigated by experiments. The results indicate that the grain size of cast billet with pulsed magnetic field was greatly refined, and the homogeneity of microstructure was improved significantly. Meanwhile, the macrosegregation and microsegregation of main alloying elements in the cast billet with pulsed magnetic field were suppressed. Compared with the conventional cast billet, the yield strength, ultimate tensile strength and elongation of the cast billet with pulsed magnetic field were increased obviously.

Effects of low-frequency electromagnetic field on nucleation during the pure aluminium solidification process

The effects of low-frequency electromagnetic field (LFEF) on nucleation during the pure aluminium solidification process are investigated. The experimental results show that the primary structure cannot be refined by applying LFEF on high-temperature liquid phase. The LFEF can dissociate the nuclei from the mould wall and disperse them uniformly when The LFEF is applied during the nucleation stage. However, the temperature at the middle of mould is higher than the liquidus temperature of pure aluminium, and the crystal nuclei cannot be preserved and grow up.