Recycling of Sintered NdFeB Magnet Wastes Using Nd85Al15 Alloy Diffusion

The cause of drawing fracture of SWRH82B wire rods was analyzed by using optical microscopy, scanning electron microscope - energy dispersive spectrometer and electron probe micro-analyzer - wavelength dispersive spectrometer. A multivariate diffusion model was established in Thermo-Cale, and the effects of temperature and time on diffusion behavior of alloys were studied. Results show that cementite network and martensite in the center area of rod is main cause of tensile fracture. There is serious segregation of chromium and manganese in the central area. The CCT curve moves to right, and critical cooling rate of martensite decreases. With high cooling rate, time for eutectoid transition is insufficient, and martensite transformation occurs in segregation band. The segregation of phosphorus further worsen the brittleness of steel. With increase of heating temperature and duration of heating time, segregation in final product is reduced, and content of cementite network and martensite decreases. When the temperature is maintained at 1050 °C for 600 s, there is no segregation of phosphorus and carbon. The diffusion of chromium is even when temperature is maintained at 1150 °C for 5400 s, and an even diffusion of manganese is obtained when temperature is maintained at 1200 °C for 3000 s. In stelmor air cooling process, the key point is keeping cooling rate low to extend holding time, and to optimize microstructure and properties.

High temperature oxidation behavior and mechanism of a new Ni-Co-based superalloy

Porous bioactive thin film on commercially pure titanium substrate was prepared by micro-arc oxidation (MAO) in electrolytic solution, which contained calcium acetate, β-glycerol phosphate disodium salt pentahydrate (β-GP) and lanthanum nitrate. The phases and microstructure of the bioactive films were examined by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectrometer and electron probe microanalysis. The results showed that: (1) porous bioactive films with about 10μm were formed on titanium substrate by MAO; (2) phases of the thin films were hydroxyapatite, anatase and rutile; (3) elements of Ca, P, and Ti of films were identified by EDS.

Hot corrosion behaviour of a Ni + CrAlYSiN composite coating in Na2SO4–25 wt.% NaCl melt

This paper discussed the effects of B2O3 addition on the crystallization of Cr-bearing phase in synthetic stainless steel slag after different duration of molten slag at 1500 oC. The crystallized slag with or without B2O3 were then characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS) and electron probe microanalysis (EPMA). The results show that B2O3 does not change the phase components of slag. However, the growth of Cr-bearing phase, magnesiochromite spinel, is enhanced and the content of Cr2O3 in the phase attains 52.66 wt.%, higher than that in the slag without B2O3.

Characterization of the shear test method with low melting point In–48Sn solder joints

The high-temperature oxidation behavior of low-carbon steel (AISI 1015, AISI 8617, AISI 4115) was investigated over the temperature range from 600 to 1000 °C in humid air containing 25% water vapor. Mass gain of oxidation measurement was performed to study the oxidation kinetics. The microstructure, thickness, and composition of the oxide scale formed were investigated via optical microscope (OM), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and electron probe microanalyzer (EPMA). The oxidation process was performed from 2 to 100 min. As the oxidation time increased, the trend of mass gain per unit area switched from a linear to a parabolic law, regardless of the steel grade used. As the chromium content increased, the duration of time during which the oxidation rate followed a linear relationship decreased. In the low-alloy steel with higher chromium content, the thickness of the mixed oxide layer containing Cr increased and the oxidation rate decreased at all oxidation temperatures.

Effects of oxygen on microstructure and evolution mechanism of body-centred-cubic molybdenum

The purpose of this study was to discuss the microstructure, recrystallization, and mechanical property evolutions in the heat-affected zones and fusion zones during dissimilar stainless steels welding. The morphology, quantity and chemical composition of the δ-ferrite were analyzed by using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and electron probe micro-analyzer (EPMA), respectively. The recrystallization phenomenon was evident with the second pass heat-affected zone (HAZ-2) and indicated equiaxed grains after second pass welding. The contents of δ-ferrite exhibited the highest value of all situations in the first pass fusion zone (FZ-1) during the first pass welding. Furthermore, the solidification mode of fusion zones transformed from massive as well as acicular δ-ferrite into lathy and skeletal structures as increased the welding pass number from 1 to 3.

The corrosion behavior of pure Fe, Cr, and Mo was studied at 125°C and 3.5 MPa solid NH4Cl + oxygen-free water vapor environment. The corrosion kinetic rates of these three metals are obtained by a weight-loss method as pure Fe > Cr > Mo. Through scanning electron microscopy, energy dispersive spectrometer, x-ray diffraction, and electron probe microanalyzer, the corrosion products, surface morphology, cross-sectional morphology, and element distribution of metals in the environment were understood. The results show that Cl− is enriched on the surface of the substrate, and participates in the corrosion reaction by the ionic cycle, which promotes the corrosion and dissolution of the metal substrate. In an oxygen-free environment, the corrosion products of metals are mainly chlorides, and a small amount of oxides are produced by hydrolysis. The corrosion rate of metal is related to the density of its surface product layer. A corrosive medium can diffuse to the surface of the substrate through the loose product layer. The denser the product layer, the more it can protect the substrate.

Amorphous structure evolution of high power diode laser cladded Fe–Co–B–Si–Nb coatings

Limestone, a sedimentary rock-forming mineral is a source of lime and is important industrially as it usually contains +95% calcium carbonate and <5% impurities. The presence of these impurities can cause problems while accessing the different applications of limestone requiring high chemical purity. Due to its great significance and multiple applications, the qualitative and quantitative analysis of limestone is highly desirable. The analysis of the emission spectrum obtained at the fundamental harmonic (1064 nm) of Q-switched Nd:YAG laser revealed the presence of Ca, Si, Al, Mg, Na, Fe, Ti, K, Sr and S with varying intensities. The Boltzmann plot method used to deduce the excitation temperature, and the electron number density value measured by the Stark broadening method resulted in the ranges from 4091–4231 K and (1.2–6.4) × 1016 cm−3, respectively. The quantitative analysis has been performed using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS) technique based on the assumption of local thermodynamic equilibrium and optically thin plasma. The results of the CF-LIBS technique were compared to the measurements of other more standard analytical methods such as scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and electron probe microanalysis with good agreement.

Experimental and finite element analysis of the shear speed effects on the Sn–Ag and Sn–Ag–Cu BGA solder joints

Graphical analysis of accelerated life test data with a mix of failure modes : Wayne Nelson. IEEE Trans. Reliab.R-24 (4), 230 (1975)

Magnesium alloys are important light metals. In recent years, they have been widely applied in the aerospace and automotive industries, and in the manufacture of communication devices, consumer-electronics appliances and computer products. However, cast magnesium and magnesium alloys are subject to problems due to gas pores, inclusion particles, oxide films, and so on. How to reduce the harm caused by these defects and refine the structure to improve casting quality has become an important topic. In this study, we evaluate the effect on casting quality of an ultrasonic method for treating the melt. The method is based on the generation of cavitation bubbles from ultrasonic treatment of the melt, which induces dispersion and degassing action. Analysis of the microstructure and determination of the mechanical properties of the resultant castings are the basis for identifying the quality of the magnesium and magnesium alloys. The microstructure was evaluated using an optical microscope and scanning electron microscopy (SEM). The elemental constituents of the inclusion particles and oxide films were identified using scanning electron microscopy in conjunction with an X-ray energy dispersive spectrometer and electron probe microanalyzer (EPMA). Finally, the mechanical properties of the magnesium and magnesium alloys, including the tensile strength, the elongation and the hardness, were also determined and discussed. In addition, variations in mechanical properties of cast aluminum and magnesium alloys by ultrasonic treatment are also discussed.