Volume 103, Issue 5

Experimental studies have been conducted to determine the primary phases and liquidus temperatures in the pseudo-binary system “SnO”–“FeO” and the pseudo-ternary system “SnO”–SiO 2 –“FeO” in equilibrium with tin–iron alloy between 1148 and 1673 K, using a high-temperature equilibration and quenching technique followed by electron probe X-ray microanalysis of the phase compositions in the quenched samples. The following primary phase fields were identified: wustite (FeO x ), spinel (Fe ( 3 – x ) Sn x O 4 ), fayalite (Fe 2 SiO 4 ), tridymite (SiO 2 ), tin iron silicate (Fe 4 Si 2 Sn 7 O 16 ), and cassiterite (SnO 2 ). With this new information on the chemistry of the “SnO”–SiO 2 –“FeO” slag this system may potentially be used for the processing and recycling of electronic scrap and the recovery of valuable minor elements.

Our recently developed model for the viscosity of borosilicate melts is extended to describe and predict the viscosities of melts containing alkali oxides. In addition to the two model parameters that are required for each B 2 O 3 – M O x melt, where M O x is a basic oxide, three more parameters are needed when M O x is an alkali oxide to account for the formation of clusters near the tetraborate composition. The additional parameters represent the size and Gibbs energy of formation of these clusters and their contribution to the activation energy of the viscous flow. A general algorithm for the calculation of the viscosity is presented which summarizes the application of the viscosity model to melts that can contain two network formers, SiO 2 and B 2 O 3 , any basic oxide and amphoteric oxides exhibiting the Charge Compensation Effect such as Al 2 O 3 . The predictive ability of the model is tested on all ternary subsystems of the B 2 O 3 –Na 2 O–K 2 O–CaO–MgO–PbO–ZnO–Al 2 O 3 –SiO 2 system containing both an alkali oxide and B 2 O 3 for which experimental data are available and on several multicomponent glass-forming melts around commercial glass compositions.

Effects of carbon and nitrogen on the structure of surface layers in high and low interstitial austenitic steels after impact wear were studied. It was shown that a fully amorphous surface layer appears in high-interstitial stainless steel. Decreasing interstitials content in austenite causes transition from the amorphous to a nanocrystal structure at the top surface. A possible mechanism of surface structure formation in these materials was considered in the frame of vacancy–interstitial interaction theory.

The development of corrosion-resistant alloys with sustained thermal and mechanical stabilities is the focus of current research on high-temperature alloys. It has been shown that the creep behavior and oxidation resistance of Co–Re alloys can be improved by small additions of, e.g., B and Zr. To understand the effect of these elements on mechanical properties, we have characterized the phases and microstructures in the Co–Re–Cr system using transmission electron microscopy. Zr forms isolated large crystals in the matrix, while B is accommodated in small intergranular (Cr,Re) 2 B borides. The incorporation of up to 23 at.% Re into the Cr 2 B structure results in increased unit cell constants. The elongated borides occur pervasively along grain boundaries, suggesting that they improve the grain boundary cohesion and thereby the mechanical properties of Co–Re–Cr alloys.

Mg-10Gd-3Y-1.8Zn-0.5Zr (wt.%) alloy is prepared by permanent mold casting and further by slow solidification at cooling rate of 0.1 K s − 1 . Both X phase with long period stacking ordered structure and DO 3 -type (Mg,Zn) 3 RE phase in the alloy are observed with electron microscopy and X-ray diffraction. Three different X phase/(Mg,Zn) 3 RE phases are observed in the alloy. The orientation relationship between X phase and (Mg,Zn) 3 RE phase was determined by the composite diffraction patterns, which can be expressed as (0014) X phase //(110) ( Mg,Zn )3RE and [110] X phase //[ 3 32] ( Mg,Zn )3RE , (0014) X phase //(110) ( Mg,Zn )3RE and [110] X phase //[ 1 11] ( Mg,Zn )3RE , (0014) X phase //(110) ( Mg,Zn )3RE and [210] X phase //[ 1 12] ( Mg,Zn )3RE . These results show coherence between X phase and (Mg,Zn) 3 RE phase and a very small mismatch in the phase boundaries.

TiO 2 films were deposited on radio-frequency-biased substrates via direct current magnetron sputtering. Argon and oxygen were used as working and reactive gases, respectively. Ions produced in the plasma are accelerated towards the substrates due to the self-bias developed at the substrates. X-ray diffraction and atomic force microscopy reveal that as-deposited films are amorphous with low surface roughness and broad, low-intensity rutile peaks are observed for the films deposited with low bias (self bias ≤ −100 V) at low substrate temperature. The optical study shows blue shift in the band gap for the films deposited with substrate bias. The structural characterization, optical analysis, and dielectric properties confirm the possible coexistence of amorphous and rutile phases in the films deposited with low-biased substrate. These films are useful as optical coatings.

In this paper, Gr5 alloy and 304 stainless steel were joined by explosive welding. In order to improve the bond strength of the clad plates, a thin (2 mm) titanium sheet was introduced as an interlayer between Gr5 and SS 304. Accordingly, microstructure, hardness, tensile-shearing, and bending tests were evaluated in detail. Optical microscopy and scanning electron microscopy revealed that the interface between Gr5 alloys and the interlayer shows a slightly wavy morphology. The interface between the interlayer and SS304 shows a wavy structure. No distinctive separation, crack, or tear were observed in both interfaces. Line scan results indicate that there is no diffusion area at both bonding interfaces. Also, tensile-shearing and bending tests results showed that the bonding is acceptable.

The cyclic texture in polycrystalline 5M Ni 50 Mn 29 Ga 21 magnetic shape-memory alloy fabricated by hot extrusion was investigated with high-energy synchrotron radiation, neutron diffraction, and electron backscatter diffraction. Combination of these techniques reveals that the texture of the hot extruded sample is quite complex. It is composed of components related to the radial direction and rotated around the extrusion axis. Additionally, the dominant texture components change from the centre to the edge of the rod. The recrystallized grains contain many twins with the trace of the twin boundaries preferentially aligned along the extrusion and radial direction showing the cyclic nature of the texture and microstructure. The results are discussed with respect to deformation mode, phase transformations, starting grain structure, and texture.

Cold hydrostatic extrusion with and without back pressure of commercial Mg 99.5+% and AZ31, AZ61, and AZ91 wrought magnesium alloys has been performed on a press operating up to 2000 MPa with a back pressure reaching up to 700 MPa. Application of back pressure extended the formability of Mg, and AZ-type magnesium alloys, which decreases with the increase in the Al content. Fibrous and elongated grains above 1 micrometre and nanometre scale sub-grains and grains were observed. The strength of all materials was significantly higher in comparison to materials conventionally and hydrostatically hot-extruded, hot ECAP-ed or after hot wire drawing. In comparison to materials processed by traditional methods the ultimate tensile strength increment after hydrostatic extrusion with back pressure increases gradually with an increase in Al content reaching for AZ91 almost 40%. The potential application of AZ-type magnesium alloys as semi-products for degradable medical implants or high strength structural components is indicated.

This study examines the response of pure Mg and its alloys, both binary Mg–Ce and ternary Mg–Al–Ce, during compression testing over a wide range of (true) strain rates and temperatures. Process maps were generated by plotting the instability parameter and efficiency of energy dissipation for microstructural evolution as a function of test temperature and strain rate. Microstructural features of each of the deformed samples were examined to generate a microstructure/micromechanism map as a matrix that was overlaid on the process map drawn in the temperature–strain-rate space. The combination of both maps delineated the desirable “safe” process window for each of the materials. Addition of 0.5% Ce to pure Mg reduced the extent of the “safe” process window despite increasing the flow stress, while alloying with both Ce and Al widened this window as determined by the extent of the desirable DRX domain. The process maps in general suggest a much wider range of temperature and strain rate for “safe” deformation compared to the microstructure maps.

Four commercial Al–Zn–Mg(–Cu) alloys have been investigated with respect to the age-hardening response and how the stage-III work-hardening behaviour is influenced by the alloying elements. Tensile specimens of the as-cast and homogenized alloys have been exposed to a solution heat treatment and a two-step age-hardening treatment with varying time at the final temperature. The work-hardening parameters obtained by fitting an extended Voce equation to the experimental stress–strain curves have been analysed and discussed. Addition of Cu was found to increase the strength, whereas Mg seemed to be a limiting factor in age-hardening potential. Accelerated precipitation kinetics was observed when the Zn content was increased.

The effect of titanium on the as-cast microstructure of a hypereutectic high-chromium cast iron was investigated by means of optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results indicate that the primary M 7 C 3 carbides are refined and spheroidized with the addition of a suitable amount of titanium. TiC is found in the primary carbide by energy dispersive spectroscopy analysis. The mechanism of titanium modification on the microstructure of the alloy is also discussed. In addition, the impact test result indicates that, compared with the hypereutectic high-chromium cast iron without titanium addition, the impact toughness value of hypereutectic high-chromium cast iron with titanium additions is improved and approximately reaches 6.4 J · cm −2 .

High-strength Ti 66 Nb 13 Cu 8 Ni 6.8 Al 6.2 composites with intermetallic matrix reinforced by nanocrystalline WC particles were fabricated via spark plasma sintering and crystallization of amorphous phase. Microstructure analysis indicates that the bulk composites contain isolated nanocrystalline WC particles surrounded by crystallized intermetallic matrix, including ductile bcc β-Ti regions surrounded by a mixed-phase region of (Cu, Ni)-Ti 2 , TiC, and remaining amorphous phase. With increasing sintering temperature the crystallized intermetallic matrix transforms from nanocrystalline to an ultrafine-grained structure. The composite with ultrafine-grained intermetallic matrix reinforced by 4.5 vol.% WC exhibits high yield and fracture strengths of 2194 and 2277 MPa, respectively. The variation of fracture strength for the fabricated composites can be explained based on the volume fraction of the crystallized ductile β-Ti phase and the scale of the crystallized phase regions.

In the present work, a new idea is presented to enhance the plasticity of Zr 65.5 Cu 22.4 Al 5.6 Ni 6.5 bulk metallic glass. A considerably large compressive plastic deformation (over 8%) was achieved by confining Zr 65.5 Cu 22.4 Al 5.6 Ni 6.5 bulk metallic glass from its center. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical conditions. It was revealed that loading induced high stress gradients facilitating large plastic strains through the generation of dense multiple shear bands.

In order to investigate the fracture behaviour of highly-alloyed Al–Zn–Mg–Cu alloys as a function of alloy purity, in-situ observations using scanning electron microscopy were performed during tensile testing. The observations were used to verify proposed fracture mechanisms in conjunction with microstructural and fractographic analyses along with fracture toughness tests. It was found that the fracture process is complex. The nucleation, growth, and coalescence of voids precede ductile fracture of the alloys. The decohesion and fracture of intermetallic particles (generally >1 μm in diameter) appears to be the initial event in the fracture process, while mechanism and propagation rate of fracture depend on the alloy chemistry. A tortuous crack path and reduced crack propagation rate in the least pure alloy can be closely related to a strong interaction of the crack front with intermetallic particles.

Because dimension stone is a natural building material, polishing is important, especially when deciding how the stone will be used. However, the effects of stone polishing are not fully understood. In the stone industry, determining the best polishing process is often performed by trial and error or is based on an expert's experiences. This paper reports the result of a study conducted using selected true marble specimens to determine their surface roughness values and to relate these values to their grain sizes, uniaxial compressive strengths, tensile strengths, and Böhme abrasion values. For this purpose, five different true marble specimens were selected. The significance and validity of the relationships between the mechanical properties and the final surface roughness values were interpreted using test statistics. It was found that there were statistically significant correlations between uniaxial compressive strength and tensile strength and the surface roughness of the studied marble specimens. It is not clearly known whether the Böhme abrasion loss value has any relationship with the surface roughness of the polished marble or not. It is thought that the present findings could help practitioners and consumers as well as architects and engineers to make more informed choices about the type of marble to use for specific applications.

This paper concerns multilayer, shielding textile-polymeric materials with a high shielding effectiveness. This effectiveness is characterised by a high capability to absorb electromagnetic fields as a result of intensification of multiple internal reflections at the boundaries between the layers of component materials. These new shielding materials present low thicknesses and surface weights, amounting to 1.0–2.0 mm and 190–420 g m − 2 , respectively, depending on their structures. Such materials composed of various structures, containing various functional particles, meet high requirements of shielding effectiveness within the frequency range tested from 8.0 to 18.0 GHz. Their absorption coefficient is at a level of ≥ 30%, and in some structures it even exceeds 90%, while the reflection coefficient is ≤ 20% and that of transmission amounts to as low as ≤ 20%, approaching even below 2%.

Immobilization of ZnO nanoparticles on cotton fabrics using poly 4-styrenesulfonic acid (PSS) was studied. The cotton fabrics were firstly cationized using 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHTAC) solution. The surfaces of cationized cotton were coated using a layer-by-layer technique by stepwise dipping the cationized cotton into a solution of anionic PSS polyelectrolyte and Zn(NO 3 ) 2 · 6H 2 O solution. The coating procedure was repeated 2, 4, and 6 times to obtain the PSS/Zn 2+ multilayers coated on the cotton fabrics. The treated cotton fabrics were hydrothermally treated in NH 4 OH solution at 90 o C for 24 h, resulting in immobilization of ZnO nanocrystals on the cotton fabrics. The SEM, XRF, and XPS data revealed the accomplishment of ZnO immobilization on the surfaces of the treated cotton fabrics. The higher the number of PSS/Zn 2+ coating layers on the fabrics, the more hydrothermally grown ZnO nanoparticles could be obtained, resulting in a higher UV protection factor when testing by the AATCC 183–2004 standard test method. All cotton fabrics with the ZnO immobilized on the surfaces were classified according to the AS/NZS 4339:1997 standard in the range of “VERY GOOD” UV protection category. The ZnO-immobilized cotton fabrics with the six PSS/Zn 2+ coating layers could inhibit the growth of Staphylococcus aureus when testing by the AATCC 147–2004 standard test method.