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The purpose of this paper is to investigate the ways to diminish or eliminate numerical diffusion and dispersion. Numerical dispersion and diffusion are present in the predicted macrosegregation profiles reported in the literature and they hinder the interpretation of the simulation results. With the motivation to eliminate these numerical problems by employing appropriate meshes, simulations of macrosegregation in a billet direct‐chill cast from a multi‐component aluminium alloy has been performed.

First the idea that numerical dispersion could be alleviated by refining the structured mesh size is tested and the extent of this mesh refining to overcome these numerical problems is discussed. Second the link of numerical dispersion and diffusion to the type of mesh used is investigated.

Unstructured mesh eliminates the numerical dispersion present in the structured mesh while it introduces the numerical diffusion. It is concluded by performing calculations with the same settings but different meshes that, although refining the structured mesh could alleviate the numerical oscillation, it increases the computation time dramatically. Therefore the best solution to overcome these numerical problems is the employment of a hybrid mesh consisting of both structured and unstructured mesh.

This work reveals the reasons behind the numerical dispersion and diffusion in macrosegregation modelling and gives a practical solution.

Additive manufacturing (AM) can achieve significant weight savings with only minor compromises in strength if high-performance wrought aluminum alloys are used as feedstock. Despite the advantages in strength that aluminum alloys (AA) 6061 offer, they cannot be manufactured via printing because of hot cracking and other solidification problems. The purpose of this study is to achieve high-quality printing of AA6061 with nanotreated wires.

Nanotreating was used to modify the AA6061 alloy composition by adding a small fraction of nanoparticles to enhance the alloy’s manufacturability and resultant properties. Wire arc additive manufacturing (WAAM) was used to print the nanotreated AA6061 wire feedstock. The microstructure of the printed AA6061 was characterized by X-ray crystallography, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy mapping. The microhardness profile, tensile behavior and fracture surface were analyzed.

This work successfully used WAAM to print nanotreated AA 6061 components. The resulting AA6061 parts were crack-free, with exceptional grain morphology and superior mechanical properties. Owing to the excellent size control capabilities of nanoparticles, a homogeneous distribution of small grains was maintained in all deposited layers, even during repeated thermal cycles.

Previous studies have not successfully printed AA6061 using WAAM. Conventional WAAM products exhibit anisotropic mechanical properties. The nanotreated AA6061 was successfully printed to achieve homogeneous microhardness and isotropic tensile properties. The promising results of this study reflect the great potential of nanotech metallurgy as applied to the WAAM process.

This paper aims to investigate the effect of ultrasonic vibration (USV) on the evolution of intermetallic compounds (IMCs), grain morphology and shear strength of soldered Ni/Sn/Ni samples.

The Ni/Sn/Ni joints were obtained through ultrasonic-assisted soldering. The formation of IMCs, their composition, grain morphology and the fractured-surface microstructures from shear tests were characterized using scanning electron microscopy and energy-dispersive x-ray spectroscopy.

Without USV, a planar interfacial Ni₃Sn₄ layer was formed at the Ni/Sn interface, and a few Ni₃Sn₄ grains were distributed in the soldered joint. The morphology of these grains was needle-shaped. With USV, several grooves were formed at the interfacial Ni₃Sn₄ layer due to ultrasonic cavitation. Some deepened grooves led to “neck” connections at the roots of the Ni₃Sn₄ grains, which accelerated the strong detachment of Ni₃Sn₄ from the substrate. In addition, two types of Ni₃Sn₄ grains, needle-shaped and granular-shaped, were observed at the interface. Furthermore, the shear strength increased with longer USV time, which was attributed to the thinning of the interfacial IMC layers and dispersion strengthening from the Ni₃Sn₄ particles distributed evenly in the joint.

The novelty of the paper is the detailed study of the effect of USV on the morphology, size changes of interfacial IMC and joint strength. This provides guidance for the application of ultrasonic-assisted soldering in electronics packaging.

The purpose of this paper is to investigate the effect of pulsed magnetic field (PMF) with different duty cycles on the melt flow and heat transfer behaviors during direct-chill (DC) casting of large-size magnesium alloy billet and find the appropriate range of duty cycle.

A transient two-dimensional mathematical model coupled electromagnetic field, flow field and thermal field, is conducted to study the melt flow and temperature field under PMF and compared with that under the harmonic magnetic field.

The results reveal that melt vibration and fluctuation are generated due to the instantaneous impact of repeated thrust and pull effects of Lorentz force under PMF. The peak of Lorentz force decreases greatly with the increasing duty cycle, but the melt fluctuation region is expanded with higher duty cycle, which accelerates the interior melt velocity and reduces the temperature gradient at the liquid-solid interface. However, PMF with overly high duty cycle has adverse effect on the melt convection and limited influence on the interior melt. A duty cycle of 20% to 50% is a reasonable range.

This paper can provide guiding significance for the setting of duty cycle parameters on DC casting under PMF.

There are few reports on the effect of PMF parameters during DC casting with applying PMF, especially for duty cycle, a parameter unique to PMF. The findings will be helpful for applying the external field of PMF on DC casting.

The purpose of this paper is to identify if the implementation of ultrasonic vibration in laser engineered net shaping (LENS) process can help to reduce internal weaknesses such as porosity, coarse primary TiB whisker and heterogeneous distribution of TiB reinforcement in the LENS-fabricated TiB reinforced Ti matrix composites (TiB-TMC) parts.

An experimental investigation is performed to achieve the results for comparative studies under different fabrication conditions through quantitative data analysis. An approach of microstructural characterization and mechanical testing is conducted to obtain the output attributes. In addition, the theoretical analysis of the physics of ultrasonic vibration in the melting materials is presented to explain the influences of ultrasonic vibration on the microstructural evolution occurred in the part fabrication.

Because of the nonlinear effects of acoustic streaming and cavitation induced by ultrasonic vibration, porosity is significantly reduced and a relatively small variation of pore sizes is achieved. Ultrasonic vibration also causes the formation of smaller TiB whiskers that distribute along grain boundaries with a homogeneous dispersion. Additionally, a quasi-continuous network (QCN) microstructure is considerably finer than that produced by LENS process without ultrasonic vibration. The refinements of both reinforcing TiB whiskers and QCN microstructural grains further improve the microhardness of TiB-TMC parts.

The novel ultrasonic vibration-assisted (UV-A) LENS process of TiB-TMC is conducted in this work for the first time to improve the process performance and part quality.

The purpose of this paper is to study the effect of feeding scheme on melt flow and temperature field during the steady-state of level-pour direct-chill (DC) casting of A390 alloy hollow billet and optimize the design of feeding scheme.

Melt flow and temperature field are investigated by numerical simulation, which is based on a three-dimensional mathematical model and well verified by experiments.

The numerical results reveal that both melt flow and temperature field are obviously affected by the feeding scheme. The homogeneity of melt flow and temperature field in hollow billet with the feeding scheme of modified four inlets are better than the other feeding schemes. Experimental results show that crack can be eliminated by increasing the number of feeding inlets. The primary Si size appears unaffected while the distribution of primary Si particles is highly affected by the change of feeding scheme. Only with the feeding scheme of modified four inlets can fine and uniformly distributed primary Si particles be achieved.

The paper includes implications for the design of feeding scheme in level-pour DC casting of hollow billet for practical use.

This paper develops different feeding schemes for level-pour DC casting of hollow billet and optimizes the design of feeding scheme.

The purpose of this paper is to investigate the influence of sprue distributions on the flow field and temperature field of the cladding casting process and verify the simulation results by experiments.

A steady-state mathematic model for the coupling of fluid flow, heat transfer and solidification to describe the process of cladding casting was present. The effect of sprue distributions on melt flow and temperature field was discussed. Based on the numerical simulation results, the cladding billet was prepared successfully. Moreover, the model has been verified against by temperature measurements during the cladding casting process.

There is a good agreement between the measured and calculated results. The homogeneity of melt flow determines the formability of cladding billets and circular temperature difference affects the bonding of the two alloys. The AA4045/AA3003 cladding billet with no defects in size of f140/f110 mm was fabricated successfully. The alloy elements diffused across the interface and formed diffusion layer with a thickness of 15 µm. The interface bonding strength is higher than the tensile strength of AA3003, indicating the metallurgical bonding between two alloys.

The casting parameters are limited to the aluminum alloy cladding billet in size of f140/f110 mm in this paper.

There are few reports of cladding billet, which are used to prepare condense pipes of automotive engines. The effect of distribution schemes on the cladding casting process is rarely studied.

The purpose of this paper is to reveal the solute segregation behavior in the molten and solidified regions during direct chill (DC) casting of a large-size magnesium alloy slab under no magnetic field (NMF), harmonic magnetic field (HMF), pulsed magnetic field (PMF) and two types of out-of-phase pulsed magnetic field (OPMF).

A 3-D multiphysical coupling mathematical model is used to evaluate the corresponding physical fields. The coupling issue is addressed using the method of separating step and result inheritance.

The results suggest that the solute deficiency tends to occur in the central part, while the solute-enriched area appears near the fillet in the molten and solidified regions. Applying magnetic field could greatly homogenize the solute field in the two-phase region. The variance of relative segregation level in the solidified cross-section under NMF is 38.1%, while it is 21.9%, 18.6%, 16.4% and 12.4% under OPMF2 (the current phase in the upper coil is ahead of the lower coil), HMF, PMF and OPMF1 (the current phase in the upper coil lags behind the lower coil), respectively, indicating that OPMF1 is more effective to reduce the macrosegregation level.

There are few reports on the solute segregation degree in rectangle slab under magnetic field, especially for magnesium alloy slab. This paper can act a reference to make clear the solute transport behavior and help reduce the macrosegregation level during DC casting.

This study describes the impact of changes in e-atmospherics in internet advertisings on consumer clicks and purchases. The study describes two unobtrusive field experiments: testing the impact of a third-party endorsement message embed in email advertising on customer clicks and purchases and testing the impact of sweepstake-award embeds in email advertising on customers’ clicks and time using brand (Blikwayski) tourism information. The studies include multiple dependent variables ranging from clicks-to-open email, clicks-to-open offer, clicks-to-purchase room rental, number-of-nights stayed and total revenue generated for the treatment versus control groups. Behaviour responses were higher for all dependent measures per participants in the treatments versus control groups. This study supports Eskin’s (1975), Cialdini’s (2006) and List’s (2011) proposal that true-field experiments can provide substantive direct evidence on the impact of alternative marketing treatments on behaviour.

The introductory chapter includes how to design-in good practices in theory, data collection procedures, analysis, and interpretations to avoid these bad practices. Given that bad practices in research are ingrained in the career training of scholars in sub-disciplines of business/management (e.g., through reading articles exhibiting bad practices usually without discussions of the severe weaknesses in these studies and by research courses stressing the use of regression analysis and structural equation modeling), this editorial is likely to have little impact. However, scholars and executives supporting good practices should not lose hope. The relevant literature includes a few brilliant contributions that can serve as beacons for eliminating the current pervasive bad practices and for performing highly competent research.