Emission Electron Probe Microanalysis Research Articles

Microstructure Modification and Enhancement in Mechanical Properties Cu/Sn-Ag/Cu Microbump Joints with 5-Micron Bonding Height Via Alloying of Zn and Ni in Cu Ubm

With the rise of artificial intelligence (AI) and the 5G era, advanced microelectronic packaging is gaining attention, shifting towards high-density interconnection and downsizing packaging structures. In response to increasing demands for high power density, low energy consumption, and low latency, 3-dimensional chip stacking technology (3D-IC) has emerged. In 3D-IC structures, Pb-free microbump solder joints, notably with diameters potentially below 10μm, are widely used, exhibiting sizes 10 times smaller than traditional flip chip joints. However, this miniaturization poses challenges, leading to interfacial Intermetallic Compound (IMC) overgrowth and high internal stress due to volume shrinkage and natural brittleness. To address this, Cu-Zn-based substrates are employed, forming a Zinc-rich layer that efficiently reduces IMC thickness. The transition of hexagonal η-Cu6Sn5 to monoclinic η'-Cu6Sn5 and the formation of porous Cu3Sn under certain conditions impact mechanical reliability. The addition of Ni and Zn in solder joints is reported to enhance phase stabilization and mechanical properties. Considering the influence of solder alloy composition on melting points, adding Zn and Ni in substrates is suggested to ensure a stable source of dopants and stabilize molten behavior. Co-doping Zn and Ni in substrates aids in Cu-Sn IMC suppression. Previous work on double-sided Cu-26Zn-18Ni substrates soldering with Sn-3.5Ag solder optimized IMC thickness, inhibiting the brittle Cu3Sn phase and Kirkendall voids, while inducing the tough γ-Cu5Zn8 phase. This phase exhibits favorable toughness and shear modulus, enhancing mechanical strength.This study investigates the microstructure evolution, elemental distribution, and mechanical reinforcement of Cu-26Zn-18Ni/Sn-3.5Ag/Cu-26Zn-18Ni microbumps with a bond height below 10μm. A field emission electron probe micro-analyzer (FE-EPMA) was utilized to examine microstructures and elemental distribution. Additionally, transmission electron microscopy with energy dispersive spectroscopy (TEM/EDS) was employed for detailed voiding formation and phase identification. Electron backscatter diffraction (EBSD) confirmed the presence of highly randomly oriented (Cu,Ni)6(Sn,Zn)5 with a submicron grain size. Fracture modes of the microbumps were characterized through shear tests and correlated with microstructures. In comparison to Cu/Sn-3.5Ag/Cu microbumps, the alternative Cu-Zn-Ni substrates significantly improved shear strength (19.6% to 97.8%) and failure toughness (10.6% to 132.1%) under different reflow times. The microstructure of Cu-26Zn-18Ni/Sn-3.5Ag/Cu-26Zn-18Ni microbumps, featuring solid solution strengthening and refined (Cu,Ni)6(Sn,Zn)5 along with tough bulk (Cu,Ag)5(Sn,Zn)8, demonstrated remarkable toughness.These findings offer valuable insights into the design of microbumps with a bonding height in the sub-10-micron scale. Keywords: Microbump, Shear strength, Microstruture, Intermetallic compounds Figure 1

The Effect of Homogenization Heat Treatment on 316L Stainless Steel Cast Billet.

This investigation aims to analyze the effect of homogenization heat treatment at 1240 °C for 2 and 6 h on the hardness, distribution, morphology, and chemical composition of the δ-ferrite and sigma phases in 316L stainless steel cast billet. A field emission scanning electron microscope, combined with electron back-scattered diffraction, a field emission electron probe microanalyzer with a wavelength dispersive spectrometer, and a Vickers microhardness tester are applied to identify various phase evolutions in the cast billet. The morphology of the δ-ferrite and sigma phases in the austenite matrix of the 316L cast billet are strongly related to the subsequent hot and cold wire drawings. The homogenization heat treatment is expected to provide a driving force to form spheroid interdendritic δ-ferrite and to minimize the amount of the brittle sigma intermetallic compound in the austenite matrix. The homogenization heat treatment at 1240 °C effectively spheroidized all δ-ferrites into blunt ones in the cast billet. The transformation of δ-ferrite into sigma is dominated by temperature and cooling rate. The fast air cooling after homogenization between 1240 and 850 °C retards the precipitation of the sigma in the δ-ferrite. There are two δ-ferrite transformation mechanisms in this experiment. The direct transformation of the δ-ferrite into sigma is observed in the as-cast 316L stainless steel billet. In contrast, the eutectoid transformation of the δ-ferrite into the sigma and austenite dominates the 316L cast billet homogenized at 1240 °C, with a slow furnace cooling rate.

Effect of controlled cooling process on the atmospheric corrosion behaviour of HRB400E hot rolled rebar

To address the problem of rusting of reinforcing bars that occurs in industry, the aim is to control the denseness of the iron oxide skin by changing the controlled cooling process without increasing the production cost, thereby improving the corrosion resistance of the bars. In this paper, the effect of different cooling control processes on the industrial atmospheric corrosion behaviour of HRB400E hot-rolled rebar was investigated using alternating wet and dry corrosion tests. The morphology and structure of iron oxide on the surface and cross-section of the rebar were observed using scanning electron microscopy (SEM) and field emission electron probe microanalysis (EPMA); the corrosion products and electrochemical behaviour of the specimens after alternating wet and dry tests were compared using x-ray diffraction analysis (XRD) and electrochemical methods. The results showed that the hot-rolled rebar without controlled cooling had a dense surface, a thicker iron oxide skin and a tighter bond between the iron oxide skin and the substrate; the corrosion rate of the hot-rolled rebar without controlled cooling was less than that of the rebar with controlled cooling in the alternating wet and dry corrosion tests; the corrosion products mainly consisted of α-FeOOH, γ-FeOOH and Fe3O4; the self-corrosion potential and rust layer resistance of the hot rolled rebar without controlled cooling after rolling are higher than those of the controlled cooling bars, showing good corrosion resistance.

A Comparative Study on Microstructure and Properties of Ultra-High-Speed Laser Cladding and Traditional Laser Cladding of Inconel625 Coatings.

In this study, ultra-high-speed laser cladding (UHSLC) and traditional low-speed laser cladding (LSLC) were employed to prepare high-quality Inconel625 coatings on 27SiMn substrates. UHSLC has cladding speeds of 30 m/min, which are 15 times faster than those of LSLC, and it produces a much greater cladding efficiency, which is 13.9 times greater than LSLC. The microstructure of the Inconel625 coatings was investigated in detail utilizing field emission scanning electron microscopy (FESEM) and electron probe microanalyzer (EPMA). According to the FESEM results, UHSLC Inconel625 coatings have more refined crystals than LSLC Inconel625 coatings. Nevertheless, the EPMA results indicate that the UHSLC Inconel625 coatings exhibit much more severe elemental segregation. Moreover, the hardness, wear and corrosion resistance of Inconel625 coatings are significantly enhanced by increasing the laser cladding speed. Furthermore, the reasons for the differences in microstructure and properties of Inconel625 coatings prepared by UHSLC and LSLC were clarified by finite element simulation. UHSLC technique is, therefore, more suitable for preparing Inconel625 coatings on 27SiMn steel surfaces than LSLC.

A novel approach for selective flotation separation of chalcopyrite and molybdenite – Electrocatalytic oxidation pretreatment and its mechanism

Electrocatalytic oxidation was adopted as a novel pretreatment method for the following selective flotation separation of chalcopyrite and molybdenite. Flotation tests of single mineral and artificial mixed ores were performed after the pretreatment of electrocatalytic oxidation, and surface analysis of the both minerals before and after the pretreatment was characterized by water contact angle, zeta potential, X-ray photoelectron spectroscopy (XPS) and field emission electron probe microanalyzer (EMPA) measurements. Flotation results showed that molybdenite could be efficient separated from chalcopyrite in the artificial mixed ores regardless of the mass ratio. Surface analysis showed that chalcopyrite was strongly depressed due to the hydrophilic oxidation products (e.g., CuO, Cu(OH)2, FeOOH and Fe2(SO4)3) were formed and precipitated on its surface after the pretreatment of EO, sharply reducing its floatability. However, the water contact angles of molybdenite surface changed hardly attributed to the rapid dissolution of oxidation products (e.g., MoO42− and SO42−) into the pulp under alkaline condition, making it keep good floatability. A highly efficient flotation separation of chalcopyrite and molybdenite was obtained via the pretreatment of electrocatalytic oxidation. Therefore, electrocatalytic oxidation pretreatment can be employed as a promising alternative for the toxic depressants of copper sulfides.

An interfacial survey on microstructure of ZrB2-based ceramics codoped with carbon fibers and SiC whiskers

The objective of this paper was to study the impact of carbon fiber (Cf) addition on the densification behavior and the microstructure formation of ZrB2 reinforced with SiC whiskers (SiCw). The spark plasma sintering (SPS) performed at 1900 °C led to a near fully dense composite as a result of the synergetic effect between SiCw and Cf on the sintering behavior of ZrB2. The field emission scanning electron microscopy (FESEM), field emission electron probe micro-analyzer (FEEPMA), and X-ray diffraction (XRD) analyses verified the unreactivity of the ZrB2-SiCw-Cf system under the applied sintering conditions. The thermodynamic study proposed the in-situ generation of B4C and ZrC compounds, although any proof could be found in neither X-ray photoelectron spectroscopy (XPS) patterns nor high-resolution transmission electron microscopy (HRTEM) images. Additionally, thanks to the nucleation and growth of new SiC and graphite phases, barely any whisker/fiber form of such additives could be observed in the micrographs. Many dislocations, originating from the plastic deformation during the SPS process and the mismatch between the thermal expansion coefficients of adjacent phases, were found in the microstructure.

Thermodynamic parameters, microstructure, and electrochemical properties of equiatomic TiMoVWCr and TiMoVNbZr high-entropy alloys prepared by vacuum arc remelting

This study investigated the thermodynamic parameters, microstructures and electrochemical properties of TiMoVWCr and TiMoVNbZr bio-refractory high-entropy alloys (bio-RHEAs) prepared using the vacuum arc remelting process. The alloys were characterized using field emission scanning electron microscopy, field emission electron probe microanalyzer, X-ray diffraction analysis, and potentiodynamic polarization tests. The determined thermodynamic values of Ω-parameter, atomic size difference and valence electron concentration for the TiMoVWCr and TiMoVNbZr bio-RHEAs were within the range of solid solution formation. A high-temperature stable single BCC1 phase was obtained using the thermodynamic equilibrium calculations for the TiMoVWCr and TiMoVNbZr systems. The TiMoVWCr alloy microstructure comprised a dendrite, an inter-dendrite, and a second phase, while TiMoVNbZr alloy comprised a dendrite and an inter-dendrite. The TiMoVWCr alloy forming the stable single body-centered cubic solid solution demonstrated homogeneous microstructure and high phase stability. Moreover, pitting resistances of TiMoVWCr and TiMoVNbZr bio-RHEAs were remarkably superior to that of ASTM F75 alloy.

Characterization of TiC ceramics with SiC and/or WC additives using electron microscopy and electron probe micro-analysis

This investigation aimed to assess the discrete and synergic impacts of SiC whiskers (SiCw) and nano-sized WC (WCn) on the microstructure of TiC-based materials. Three dense specimens of TiC−3 wt% WCn, TiC−30 vol% SiCw, and TiC−30 vol% SiCw−3 wt% WCn were yielded using the spark plasma sintering (SPS). The X-ray diffraction patterns (XRD), as well as the microstructural observations, suggested unreactive sintering processes; however, thermodynamic studies showed that some minor chemical interactions could take place, leading to surface oxide removal. Furthermore, the field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) micrographs, as well as the field emission electron probe micro-analyzer (FEEPMA) images, proved the WCn dissolution into the TiC matrix, forming (Ti,W)C solid solution in the TiC-WCn and TiC-SiCw-WCn ceramics, and also the graphite precipitation from the TiC in all samples. Glassy SiO2 phase, available as the surface oxide of starting SiCw or produced as the in-situ phase, could form some amorphous interfaces in the relevant composites.

Improvement of CrMoN/SiNx coatings on mechanical and high temperature Tribological properties through biomimetic laminated structure design

CrMoN/SiNx multilayered coatings were fabricated by controlling the shutter-open time of two sputtering guns in a radio frequency magnetron sputtering system. Employing the structure of nacreous shells from nature, nano-crystalline and amorphous monolayers were periodically stacked. CrMoN/SiNx thin films with different bi-layer periods were deposited on Si-wafer and Inconel-718 substrates. The phases of the coatings were examined using a grazing incidence X-ray diffraction (XRD) technique. Information of chemical composition was obtained by field emission electron probe micro-analyzer (FE-EPMA). The confirmation of multilayer structure was observed by transmission electron microscope (TEM). The wear tracks were revealed by scanning electron microscope (SEM). Mechanical and high-temperature tribological properties were evaluated using a nano-indenter and a high-temperature tribometer, respectively.Grain refinement phenomenon was verified using XRD peak broadening at high angles, indicating inhibition in the column structure and the formation of an amorphous phase. CrMoN/SiNx exhibited higher high-temperature wear resistance for a specific bi-layer period, which was attributed to the multilayer strengthening mechanism. Multilayered structure provided tremendous benefit to COF improvement, which was reduced by 50% of the value of CrMoN. Simultaneously, the toughening effect of the biomimetic structure design improved the wear resistance ability of the coating. Especially, the slight amount of SiNx unpredictably enhanced the wearing properties of the system, which is in consistent with the role of chitin in nacre. Moreover, an optimal bi-layer period was identified, resulting in optimal mechanical properties that were consistent with the high-temperature tribological properties. Furthermore, the wear tracks on the specimens were analyzed through field-emission scanning electron microscopy, which support the wearing behavior alteration. Finally, a CrMoN/SiNx multilayer coating with optimal high-temperature characteristics was demonstrated in this study.

Recycling of scrap metal into artisanal cookware

TPS 721: Low and middle income countries: e-waste, occupational health, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Background: In South Africa, the use of artisanal cookware made from the recycling of scrap metal is widespread. However, the potential of metal exposure from the use of such cookware has not been investigated. The aim of the study was to determine the risk of metal exposure posed by artisanal cookware available in South Africa to end users. Methods: Twenty cookware samples were purchased from across South Africa. Aluminum and silicon concentrations were determined using XRF and the total content of 18 elements (Ag, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn) were determined with ICP-MS. To investigate the leaching of metals, artisanal cookware pieces were boiled in a 3% acetic acid solution over a 2-hour period and each experiment was repeated three times. Post leaching, secondary electron images were obtained with a JEOL Field Emission Electron Probe Microanalyzer. Results: The total aluminum (Al) content ranged from 67% to 93%. Silicon was the second most abundant element with a mean of 13.8 %. The mean Al migration of 509 mg L-1 was over 100 times the maximum permissible level allowed for cookware. Lead was detected in all samples with numerous samples highlighting cause for concern. Cadmium and mercury were detected in all pots across all three migrations. However the levels were low (highest levels detected were 1.6 ug L-1 and 0.26 ug L-1 respectively). Transmission electron microscopy revealed dramatic change in surface structure after leaching of cookware. Conclusion: Public awareness on multi-metal exposure and related risks from the use of artisanal cookware should be a public health priority in relevant settings.

The analysis of the self-lubricating behavior and local failure mechanism of silver-rich solid film

PurposeThe main aim of this paper was to study the self-lubricating behavior and failure mechanism of silver-rich solid film for in-depth analyzing of the friction and wear property of TiAl-10 wt. per cent Ag self-lubricating composite.Design/methodology/approachThe friction and wear property of TiAl-10 wt. per cent Ag self-lubricating composite sliding against Si3N4 ball was tested under the testing conditions of ball-on-disk wear system. Field emission scanning electron microscopy and electron probe microanalyzer were used to analyze the surface morphology of silver-rich solid film. The main element contents were tested by energy dispersive spectroscopy. Silver phase on wear scar could be well identified using X-ray photo-electron spectroscopy. The theory calculation of shearing stress on wear scar was executed to discuss the local failure mechanism of silver-rich solid film. The lubricating role of silver was also discussed to analyze the anti-friction and anti-wear behavior of silver-rich solid film.FindingsThe friction coefficients and wear rates of TASC gradually reduced at 0-65 min, and approached to small values (0.31 in friction coefficient and 3.10×104 mm3N-1m-1 in wear rate) at 65-75 min. The excellent friction and wear behavior of TASC was mainly attributed to the lubricating property of silver-rich film at 65-75 min. At 12→20 N, surface shearing stress increased up to 146.31 MPa, and exceeded more than the shearing strength (125 MPa) of silver-rich film, which caused the propagating of fatigue crack and the destroying of silver-rich film, leading to high friction and severe wear.Originality/valueIt is important that the self-lubricating behavior and local failure of solid film is explored for further understanding the friction and wear property of TiAl alloys.

Water-Rock Interactions in Outer Solar System Bodies: Evidence from the Coordinated Analysis of Interplanetary Dust

NASA has an ongoing program of collecting interplanetary dust particles (IDPs) in the stratosphere using high altitude research aircraft. The collected IDPs are derived from asteroids and comets and here we report studies of a subset of hydrated IDPs rich in carbonaceous matter that are proposed to have a cometary origin. Our studies are aimed at understanding the evolution of oxygen reservoirs in the Solar System and their interaction with cometary minerals and organic matter. The small size (<20 μm) and fragility of these IDPs present a number of analytical challenges. We have pioneered techniques for performing chemical, mineralogical, isotopic, and spectroscopic measurements on the same sample in a carefully coordinated sequence. Coordinated analyses of nanogram-size samples is made possible by several delicate sample preparation techniques. To avoid organic contamination, we embed IDPs in elemental sulfur and use ultramicrotomy to partly section the particles (the first few micrometers). Multiple thin sections (50-70 nm thick) are placed on different substrates depending on the analysis technique. We use a JEOL 2500SE scanning, transmission electron microscope (STEM) to determine the mineralogy, microstructure, and elemental compositions of constituent minerals in the thin sections through a combination of high resolution imaging, electron diffraction, quantitative energy-dispersive x-ray mapping, and electron energy-loss spectroscopy. Following the STEM analyses, we use a NanoSIMS 50L for high spatial resolution isotopic measurements of H, C, N, and O to search for presolar grains and to understand the origin of the indigenous organic matter. The isotopic analyses are performed on the same sections analyzed in the STEM in order to correlate isotopic properties with the elemental and mineralogical data. We reserve other thin sections for non-destructive analyses utilizing synchrotron-based techniques including Fourier-transform infrared (FTIR) micro-spectroscopy and X-ray absorption near-edge structure (XANES) analyses, especially for functional group analysis of organic matter in the particles. The remainder of the IDP is extracted from the sulfur bead that was used for microtomy and is pressed into Au foil for quantitative analysis (including light elements) using a JEOL 8530F field emission electron probe microanalyzer (EPMA). After the EPMA measurements, high precision oxygen isotopic analyses are obtained using Cameca IMS1270/1290 instruments at UCLA. The hydrated IDPs in this study are dominated by saponitic clays, with minor magnetite, carbonate and abundant organic matter. The remarkable oxygen isotopic compositions, high carbon contents, and the abundance of isotopically anomalous organic matter, together suggest that the high carbon, hydrated IDPs are derived from primitive sources not yet represented in meteorite collections such as outer main belt P- and D-type asteroids or comets.

The development of a Zr-Cu-Al-Ag-N thin film metallic glass coating in pursuit of improved mechanical, corrosion, and antimicrobial property for bio-medical application

The amorphous thin film metallic glass (TFMGs) is a promising material with superior mechanical performance, fatigue properties, corrosion resistance, unique thermal properties, and antimicrobial efficacy. In this study, newly-designed Zr-Cu-Al-Ag-N TFMGs with various nitrogen content were fabricated by adjusting the nitrogen flow rate into the vacuum chamber. The composition of the Zr-Cu-Al-Ag-N thin films were analyzed by field emission electron probe micro-analyzer (FE-EPMA). The amorphous structure of the thin films were examined with grazing angle X-ray diffractometer (GIXRD). The differential scanning calorimetry (DSC) was applied to identify the amorphous characteristics and thermal properties of the thin films. The high resolution transmission electron microscopy (HR-TEM) was used to observe the microstructure and short range order (SRO) structure of the coatings. For a better intrinsic viewpoint, the average interatomic distance was calculated. The calculated distance gets closer with the increasing nitrogen content, which might result from the increase of short range order (SRO) structure. The nano-hardness, elastic modulus were measured with the aid of a nanoindentation tester. A positive relationship between nitrogen content and mechanical properties was acquired. The potentiostat testing and corroded surface observation were executed to quantitatively and qualitatively evaluate the corrosion resistance of the coatings. It is revealed that the corrosion resistance is enhanced as the increasing nitrogen content, which is attributed to the denser-packed structure. To access the antimicrobial performance of the coatings, liquid culture and plate counting method are used under the regulation of Japanese Industrial Standard (JIS Z2801:2000). It is revealed that the antimicrobial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is over 99.999% for all the TFMG coatings, which is attributed to the ultra-smooth surface roughness and Cu/Ag-containing chemical composition. Finally, the composition of Zr-Cu-Al-Ag-N TFMG with superior mechanical properties, thermal stability, corrosion resistance and antimicrobial efficacy will be revealed and discussed.

The effect of incorporated self-lubricated BN(h) particles on the tribological properties of Ni–P/BN(h) composite coatings

Ni–P/BN(h) composite coatings are prepared by means of the conventional electroless plating from the bath containing up to 10.0g/l of hexagonal boron nitride particles with size 0.5μm. The Ni–P coating is also prepared as a comparison. Cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to stabilize the electrolyte, and the optimum CTAB concentration resulting in a nonagglomerated dispersion of particles is obtained using a dispersion stability analyzer. Morphology of the coatings and the effect of incorporated particles on coating structure and composition are investigated via scanning electron microscopy, field emission electron probe micro-analyzer and X-ray diffraction analysis. Hardness, roughness, friction coefficient and wear resistance of the coatings are also evaluated using Vickers microhardness tester, atomic force microscopy and ball-on disk machine. The presence of CTAB in the depositing bath has a positive effect on the surface roughness and performance of Ni–P/BN(h) composite coatings. The friction and wear tests results show that incorporation of 14.5vol% BN(h) particles into the Ni–P coating lowers the coating friction coefficient by about 75% and the wear resistance of the Ni–P composites is approximately 10 times higher than Ni–P coating.

Applying composition control to improve the mechanical and thermal properties of Zr–Cu–Ni–Al thin film metallic glass by magnetron DC sputtering

This study is intended to investigate the amorphicity region of Ni+Al content in Zr–Cu–Ni–Al thin film. The thermal and mechanical performances of Zr–Cu–Ni–Al thin film metallic glass (TFMG) are also addressed. By adjusting target power, thin film metallic glass with various (Zr+Cu)/(Ni+Al) ratio were fabricated. The composition of the Zr–Cu–Ni–Al thin films was analyzed by field emission electron probe micro-analyzer (FE-EPMA). Via Grazing Angle X-Ray Diffractometer (GIXRD), all Zr–Cu–Ni–Al thin films show the hump peak, implying the amorphous feature. To further identify the amorphous characteristic, a differential scanning calorimetry (DSC) is used and the amorphicity region of (Ni+Al) in Zr–Cu–Ni–Al thin film is as wide as 54at.%. Besides, the glass transition temperature Tg, for all Zr–Cu–Ni–Al TFMGs are above 700K, and the △T ranges from 50K to 70K. With the aid of nano-indention, hardness and elastic modulus were measured in which the hardness reaches 7.5GPa for Zr23Cu23Ni27Al27 TFMG. The value of △T increases with (Ni+Al) contents in Zr–Cu–Ni–Al TFMG across the whole amorphous region, indicating that the thermal stability is improved and higher hardness is thus achieved. For a better intrinsic viewpoint, the average interatomic distance is calculated. The calculated distance gets closer with Ni+Al content, which might result from the increase of short range order (SRO) structure with good thermal stability. From the positive correlation of elastic modulus and Ni+Al content, the improved hardness is explained in the viewpoint of energy. In summary, the thermal and mechanical performances of Zr–Cu–Ni–Al TFMG with 54at.% (Ni+Al) content are among the best in the class of Zr–Cu–Ni–Al metallic glass, implying that Zr–Cu–Ni–Al TFMG with improved performance can be fabricated in lower cost.

Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in γ-Fe temperature region

Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ- Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ- Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.

Observation of changes in the metallurgical characteristics of Ni-Cr alloys using Nd:YAG laser welding

This study aimed to determine the effect of hardness change according to penetration depth in the laser fusing zone and observed the correlation of the microstructure as an Nd:YAG laser was irradiated to Ni-Cr alloy for dental use by setting the spot diameter size to various conditions. In all groups, the hardness depth profiles in the laser fusing zone and heat-affected zone (HAZ) had larger values than those of the base metal. In addition, the hardness values in places beyond the fusing zone and the HAZ were measured as being quantitatively lower. The observation result of the diffusion of the constituent elements and microstructure using field emission scanning electron microscopy, energy-dispersive spectroscopy, and electron probe microanalyzer showed that the fusing zone revealed a much finer dendritic form than the base metal due to the self-quenching effect after welding, while no change in constituent elements was found although some evaporation of the main elements was observed. In addition, Mo- and Si-combined intermetallic compounds were formed on the interdendritic area. Through this study, the laser fusing zone had better hardenability due to the intermetallic compound and grain refinement effect.

Antimicrobial characteristics in Cu-containing Zr-based thin film metallic glass

Zr-based thin film metallic glass (TFMG), exhibiting the unique properties of good glass forming ability (GFA), corrosion resistance, and biocompatibility, can be applied in various novel fields of industries. An ultra-smooth surface is obtained with the TFMG coatings, which is beneficial to modify the work surface. Thus, TFMG can be extended to medical appliances, such as surgical blades and micro-surgery scissors. The aims of this study are to fabricate the Cu-containing Zr-based TFMG onto SUS304 plates and to investigate the surface physical properties and their antimicrobial effects. The chemical compositions of Zr–Cu–Ni–Al coatings are examined by a field emission electron probe micro-analyzer (FE-EPMA). The amorphous structures of all TFMG are characterized by the X-ray diffractometry. The surface properties are analyzed by an atomic force microscope (AFM) and a water contact angle goniometer for the 304 stainless steel substrate and Zr–Cu–Ni–Al TFMG. Liquid culture methods and plate counting methods are used to assess the antimicrobial performance of specimens. The antimicrobial rate against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under the Japanese Industrial Standard JIS Z2801: 2000 is over 99%. The release of copper ion from TFMG specimen is determined by the inductively coupled plasma-mass spectrometer (ICP-MS) to evaluate the antimicrobial activity of Cu-containing Zr-based TFMG. The results show that the surface of SUS 304 stainless steel substrate can be modified with deposited Zr–Cu–Ni–Al TFMG, and their improved antimicrobial efficacy against those bacteria is attributed to their amorphous rough surface, hydrophobic properties and released copper ion. The TFMG developed in this study with adequate hardness, good adhesion ability and antimicrobial efficiencies can be used as a promising candidate to improve the surface properties of the medical appliances and also to reduce the possibility of nosocomial infection.

Isothermal Bainite Transformation in Low Silicon TRIP Steel with Phosphorus Addition

The low silicon transformation-induced plasticity (TRIP) steel with phosphorus addition is consisted of the microstructure of retained austenite, ferrite and bainite which produced by intercritical annealing and isothermal bainite transformation followed by rapid cooling. In this study, isothermal bainite transformation of different experimental parameters in low silicon TRIP steel with phosphorus addition was investigated in laboratory. The addition of cheap element phosphorus, which has the same effect of silicon in retard the kinetics of carbide formation during isothermal bainite transformation, can reduce the silicon content, improve surface quality, solve galvanizing problem and reduce costs. The effect of bainite isothermal temperature, intercritical annealing temperature and heating rates were investigated by dilatometric experiment on a push-rod Formastor-FII high-speed dilatometer with radio frequency induction heating. The high resolution observations, composition analysis and elements distribution of microstructure were carried out using the electron scanning microscopy of a field emission electron probe microanalyzer (JEOL JXA-8530F) operating at 20KV accelerating voltage.

Compatibility of Ni and F82H with liquid Pb–Li under rotating flow

The present study reports the compatibility of a reduced-activation ferritic steel F82H and Ni with liquid Pb–Li under rotating flow conditions at 600°C. Cross-sectional observation of Ni using field emission electron probe micro-analyzer (FE-EPMA) after exposure for 100h revealed that severe grain boundary penetration of Pb into Ni occurred up to approximately a depth of 700μm, causing liquid metal embrittlement (LME). In contrast, the results for F82H after exposure for 500h showed the formation of pitting holes and a Cr-depleted layer at the surface with an approximate maximum depth of 10μm. Oxide particles were also found in the Pb–Li region in the F82H specimen after exposure. The radio-frequency glow discharge spectrometers successfully detected Li and indicated Li oxide formation at the surface.