The constitution of the ternary system Al–Cu–Fe in the region above 40 at.% Al at 600 °C is investigated by means of x-ray diffraction, metallography, scanning electron microanalysis, energy dispersive x-ray spectroscopy, and differential thermal analysis. The phase equilibria in the Al-rich corner are clarified by the valuable experimental evidence for the four-phase reaction L + λFe4Al13 ↔ (Al) + ω at 600.7 °C and experimental findings that the phase αFe4CuAl23 was not detected. A thermodynamic model of the Al–Cu–Fe system was then performed over the entire composition range by taking into account the phase diagram data above 560 °C from the literature and the present work. This work challenged the modeling of the considerably complex order–disorder phase transition between bcc_A2 and bcc_B2 phases and the miscibility gap of bcc_B2 phase using the modified sublattice model.

Nb can improve the oxidation resistance of TiAl; however, the reported concomitant effects on the mechanical properties are controversial. Therefore, the effect of different Nb additions (0∼20.83 at.% Nb) on the lattice distortion as well as dislocation nucleation and mobility of TiAl were examined by density-functional theory calculations to solve the puzzle. The calculation of the formation energy and c/a ratio showed that Nb slightly decreases the phase stability and enhances the anisotropy. The variation of shearing energy barrier demonstrates an interesting staged strengthening effect of Nb on TiAl. Further analyses of the charge density difference and the partial density of states reveal that the physical origination is the electronic anisotropy, which is correlated with the Nb content and distribution.

The refinement mechanism of pulsed magnetic field (PMF) was discussed by experimental investigation, and the effects of exciting frequency, exciting voltage, and delay time of PMF on grains refinement of superalloy were studied. The experimental results show that, as exciting frequency or exciting voltage is increased, the grains are refined. However, the grains become coarse when frequency increases further. As delay time of PMF increases, the grain size increases. The refinement effect of PMF is attributed to the detachment of heterogeneous nuclei on the mold wall and subsequently separation of nuclei in the melt. The Joule heat can prolong the continuous nucleation process. However, the refinement effect will be impaired if the Joule heat is strong enough to remelt the detached nuclei.

Multichannel acoustic emission (AE) measurements by four laser interferometers were developed and applied during a plasma-spray coating process that is known as being a high-temperature process and an extremely noisy environment in both mechanical and electrical domains. The AE signals could be successfully detected during the cooling period after the deposition, and it was clearly indicated that a higher preheating temperature resulted in the improvement of bonding between splats and/or at the interface of the coating and the substrate. The maximum principal stress generated during the deposition process was calculated by the transient heat and stress analysis and the obtained AE events. The critical stress for crack initiation of the alumina coating on a steel substrate with an NiCr bond coat layer was estimated as 30∼45 MPa. The developed techniques were shown to be a potential tool for in situ monitoring of the thermal spray process, by which an increase in the reliability of thermal spray coatings can be expected.

We performed density-functional calculations of oxygen incorporation and diffusion in layered Ti2AlC for a range of intrinsic- and impurity-element chemical potentials. In view of the thermal equilibrium coexistence between oxygen-dissolved Ti2AlC and the oxide scale, a thermodynamic scheme is presented that allows the comparison of the relative stability of oxygen defects in different exterior environments. The calculations show that the oxygen atom favors substitution on carbon lattice sites (OC) under oxygen-lean conditions and high temperatures, whereas the occurrence of an oxygen interstitial in the aluminum atomic layer (IO-tri) becomes more preferential in an oxygen-rich atmosphere and low temperatures. Interstitial oxygen (IO-tri) diffusion via a metastable interstitial site (IO-oct) has a comparatively low migration energy. The substitutional oxygen defect (OC) diffuses by exchanging with neighboring carbon vacancy, which needs a relatively high diffusion barrier.

The ignition and reaction mechanisms of the thermal explosion reaction in the Ni-Ti-C system under air and Ar conditions were investigated. The reaction for the formation of TiC can be initiated at a low temperature under air. The ignition temperature under air is much lower than that under Ar. Under Ar, both the ignition and reaction mechanisms consist of dissolution, reaction, and precipitation. Under air, the ignition mechanism is confirmed to be the chemical oven mechanism, and the reaction mechanism is dissolution, reaction, and precipitation. The mechanism of gas transport plays a much more minor role in the ignition and reaction processes under air.

Zr–N films were grown on glass and Si (100) substrate by radio-frequency magnetron sputtering using a mixture of high pure nitrogen and argon as sputtering gases. The structure and properties of Zr–N compounds in the films change with N2/(N2+Ar) flow ratio (RN2). At low RN2, a ZrN alloy with the rocksalt structure (denoted as γ-ZrNx) is formed. The N concentration x and lattice constant increases with increasing RN2, and x reaches 1 when the RN2 goes up to 20%. As the RN2 exceeds 20%, the film is composed of γ-ZrN and Zr3N4 phase with Th3P4 structure (denoted as c-Zr3N4). The relative content decreases for the γ-ZrN but increases for the c-Zr3N4 with increasing RN2, and a single phase of c-Zr3N4 was deposited on glass at RN2 of 100%. The c-Zr3N4 behaves with p-type conductivity with a band gap of 2.8 eV. The lattice constant of the c-Zr3N4 was measured to be ∼0.674 nm. The mechanism of the phase transition from γ-ZrN to c-Zr3N4 with increasing RN2 was suggested.

The effect of porosity on the kinetics of the austenite to bainite isothermal transformation in powder metallurgy steels was characterized using a high-speed quenching dilatometer. The measurements revealed that the presence of porosity shortens the incubation time as well as the overall isothermal transformation time. An Avrami-type equation was fitted to the measured data, and the effect of porosity on the nucleation rate of bainite was quantified. In addition, the activation energy for diffusion of carbon atoms during nucleation of bainite was calculated and was found to decrease with increasing porosity.

This work investigates the coating of nano- to submicron-sized hollow nickel particles onto Al powders to optimize the thermal and combustion properties of Al-based energetic materials. Different wt% of hollow nickel particles coated onto Al particles was synthesized using an autocatalytic aqueous reduction method. X-ray diffraction results showed distinct crystalline Al and Ni phases indicating that a pure coating process was achieved. Homogeneous coating of hollow nickel particles onto individual Al particles was also reflected from the scanning electron microscope images. All the samples showed significant improvements in terms of their ignition and kinetics of combustion as compared to untreated Al. The most promising candidate produced was the 30wt%Ni–Al sample whereby the %complete combustion of Al exhibited the largest improvement. The hollow Ni-coated Al samples were also found to perform better than their physically mixed Ni–Al powder samples, as there is more intimate contact between the two components to hasten the overall combustion kinetics.

Microstructure features of five electrodeposited coppers with different grain sizes were systematically characterized by using transmission electron microscopy (TEM) observations and x-ray diffraction (XRD) analysis. Based on the experimental observations, two mechanisms for the grain refinement in electrodeposited copper were identified: (i) twin–twin intersection can directly create grains with large-angle boundaries as small as 10 nm and (ii) grains can also be refined via formation of dislocation cells, transformation of dislocation cell walls into sub-boundaries with small misorientations, and evolution of sub-boundaries into highly misoriented grain boundaries. Besides, dislocations are also effective to cut twin lamellas into pieces and make twin boundaries curved and round.

Dispersed crystalline copper particles were prepared by reacting aqueous dispersions of CuCl with ferrous citrate. We report that the Fe(II) citrate complex can reduce rapidly and completely cuprous chloride to metallic copper and propose a mechanism for the reaction observed. By changing the precipitation conditions, copper particles with sizes varying from 250 nm to 2.0 µm were obtained. The method described represents a simple and versatile approach for preparing copper powders for electronic applications.

A simple approach, order–disorder transition (ODT), has been developed to synthesize a novel glass using ZSM-5 as starting materials. In this process, the ZSM-5 powders were pressed uniaxially in a graphite die and rapidly sintered using spark plasma sintering (SPS). High-resolution transmission electron microscopic images revealed that a few crystalline zeolite fragments were still preserved locally inside the SPS consolidated sample. Vickers microhardness and fracture toughness of this as-prepared transparent glass sample at room temperature reaches 7.3 ± 0.2 GPa and 2.0 ± 0.3MPa·m1/2, respectively. It is very interesting that these novel bulk transparent glasses exhibit ultraviolet photoluminescence (PL) properties at about ∼360 nm.