Thermomechanical processing of Ti–5Al–5Mo–5V–3Cr

The constitutive behaviour and microstructural evolution of the near-β alloy Ti–5Al–5Mo–5V–3Cr in the α + β condition has been characterised during isothermal subtransus forging at a range of temperatures and strain rates. The results indicate that Ti–5Al–5Mo–5V–3Cr has a shallower approach curve, and therefore, offers a more controllable microstructure than the near-β alloy Ti–10V–2Fe–3Al. Flow softening is small in magnitude in both alloys in the α + β condition. The steady state flow stresses obey a Norton–Hoff constitutive law with an activation energy of Q = 183 kJ mol⁻¹, which is similar to the activation energy for self-diffusion in the β phase, suggesting deformation is dominated by dynamic recovery in the β matrix. Good evidence is found for the existence of ω phase after both air cooling and water quenching from above the β transus. In addition, dissolution of the α phase is found to be slow at near-transus temperatures.     

D.c. conductivity of V2O5–MnO–TeO2 glasses

Semiconductive oxide glasses in the system V2O5–MnO–TeO2 were prepared, and the mechanism of d.c. conduction was studied. The Seebeck coefficient measurements at temperatures from 375–475 K indicated the glasses to be n-type semiconducting. The d.c. conductivity ranged from 5×10–5 to 1.9×10–6 S cm–1 at 405 K for V2O5=60 mol% and MnO=0–20 mol%, and decreased with increasing MnO content. The conduction was confirmed to obey the adiabatic small polaron hopping model, and was due to mainly hopping between V-ions in the glasses. The polaron band width J was estimated to be J=0.10–0.20 eV. The electron–phonon interaction coefficient p was very large (21–26). The hopping mobility evaluated as 2.3×10–7–2.7×10–6 cm2 V–1 s–1 increased with increasing V2O5 content. The estimated carrier concentration was the order of 1019 cm–3. The principal factor determining conductivity was the polaron hopping mobility in these glasses. © 1998 Chapman & Hall     

Mechanical properties of the hot-rolled Mg–12Gd–3Y magnesium alloy

Tensile and high cycle fatigue (HCF) properties of the hot-rolled Mg–12Gd–3Y (wt.%) magnesium alloy have been investigated. The magnesium alloy exhibits a fatigue strength of about 150 MPa, which is much higher than that of the commercial Mg–8Al–Zn alloy AZ80. Aging heat-treatment (T5) improved the fatigue life of the Mg–12Gd–3Y alloy. Fatigue cracks nucleated at the intense slip bands in the as-rolled alloy. After T5 treatment, however, the fatigue crack nucleation site shifted to the phase boundaries between MgGdY particles and Mg matrix. T5 heat-treatment retarded the crack initiation and thus improved the fatigue life of the Mg–12Gd–3Y alloy.     

Evaluation of Mn substitution for Ni in alumina-forming austenitic stainless steels

There has been increasing interest in the substitution of low-cost Mn for Ni in austenitic stainless steels due to the rising price of Ni. This paper investigates the possibility of such a substitution approach for the recently developed alumina (Al₂O₃)-forming austenitic (AFA) class of heat-resistant stainless steels. Computational thermodynamic tools were utilized to predict the alloy composition range to maintain an austenitic matrix microstructure when Mn is substituted for Ni in the presence of Al, which is a strong body-centered-cubic (BCC) phase stabilizer. Phase equilibria, oxidation behavior, and creep properties of Fe–(10–14)Cr–(5–15)Mn–(4–12)Ni–(2.5–3)Al–Cu–Nb–C–B (in weight percent) based alloys were studied. The alloys based on Fe–14Cr–2.5Al–(5–9)Mn–(10–12)Ni exhibited the best balance of oxidation and creep resistance, which represents approximately 50% reduction in Ni content compared to previously developed AFA alloys. These low-Ni, high-Mn AFA alloys formed protective Al₂O₃ scales up to 973–1073 K in air and at 923 K in air with 10% water vapor. Creep-rupture lives of the alloys under a severe screening condition of 1023 K and 100 MPa were in the 7.2 × 10⁵–1.8 × 10⁶ s (200–500 h) range, which is comparable to or somewhat improved over that of type 347 stainless steel (Fe–18Cr–11Ni base).     

Magnetic properties of Nd–Fe–B/FeMn multilayer films

[Nd–Fe–B(x nm)/FeMn(d nm)]_n thin films were deposited by magnetron sputtering on Si (100) substrates heated at 650 °C. The influence of the composition and thickness of FeMn layer on the structure and magnetic properties of Nd–Fe–B films are investigated. The Nd–Fe–B/FeMn multilayer films present an enhanced coercivity and a reduced saturation magnetization, in comparison with those of a Nd–Fe–B single layer. The coercivity of [Nd–Fe–B(x nm)/FeMn(5 nm)]_n films increases with increasing the period number of FeMn layer for the same thickness of magnetic layer, while the coercivity in [Nd–Fe–B(50 nm)/FeMn(5 nm)]_n films increases with decreasing the period number of Nd–Fe–B/FeMn bilayers. The coercivity H_c of about 17.2 kOe is achieved in the Nd–Fe–B(50 nm)/FeMn(5 nm) film.     

Experimental analysis of tensile properties of some suturing materials

The aim of the investigation is to quantitatively evaluate the failure load of several suture materials currently used in dentistry surgery. No chromic catgut, silk, Prolene, Ethilon, Ethibond, Vicryl and Vicryl Rapid, obtained from Ethicon s.p.a., in the sizes 3–0, 4–0, and 5–0 have been tested. The analysis has been carried out measuring the diameter of each suture with an optical microscope to determine the accuracy of manufacturers data. Tensile testing has been performed to evaluate the failure load of each material. Finally, sutures of the same effective diameter class have been compared relative to failure load. Results show that monofilament sutures present a failure load remarkably superior to that of multifilament sutures. Using SEM analysis monofilament sutures present less surface irregularities than multifilament sutures. Only monofilaments Ethilon 4–0 and 5–0, Prolene 4–0, and multifilament no chromic catgut 4–0 and 5–0 meet the requirements of the Italian Pharmacopeia. In contrast, Prolene 5–0 and the other multifilaments, silk, Ethibond, Vicryl and Vicryl rapid, have a larger diameter than that declared on the label by the producer.     

Amorphization Behavior and Nanocrystalline Structure of Fe–P–Si–V Alloys

It is found that Fe–P–Si–V alloys tend to be in an amorphous state on cooling at a rate of 10⁵to 10⁶K/s. As compared to Fe–P–Si alloys, the crystallization behavior of the Fe–P–Si–V alloys is more complex owing to the formation of both metastable and equilibrium silicides. The metastable phases are nanocrystalline, as evidenced by transmission electron microscopy, which ensures a noticeable strength gain.     

Dielectric spectra of fresh cement paste below freezing point using an insulated electrode

The spectra of complex dielectric constant were measured on a fresh cement paste with a water/cement ratio of 0.4 sandwiched between insulated electrodes in the frequency range 10 kHz–1 MHz and temperature range between 0 °C and — 30 °C. The bulk dielectric constant, 30–20, and conductivity, 6.14×10^–5–0.65×10^–5, in the temperature range –10 to –28 °C were much lower than those at room temperature, owing to the great decrease of ionic mobility caused by freezing the cement paste. The activation energy of 0.31 eV for the ionic conduction in fresh cement paste was obtained from an Arrhenius plot of conductivity at subzero temperature.     

Microstructure, mechanical properties and aging behavior of Mg–5Li–3Al–2Zn–xAg

Mg–5Li–3Al–2Zn–xAg (x = 0, 0.1, 0.3, 0.6, 1.2) alloys were prepared by medium-frequency induction furnace under the ambient of pure argon. The effect of Ag addition on the microstructure, tensile properties, and aging behavior was investigated. Results show that the addition of Ag can restrain the decomposition from MgAlLi₂ to AlLi. With the addition of Ag, the over-aging point is retarded and the over-aging phenomenon is avoided in Mg–5Li–3Al–2Zn–1.2Ag. The solid solution of Ag in matrix phases and the restraining of the decomposition from MgAlLi₂ to AlLi are two aspects that strengthen the alloys.     

Effects of Al–5Ti–1B and Al–5Zr master alloys on the structure, hardness and tensile properties of a highly alloyed aluminum alloy

This study was undertaken to investigate the influence of Al–5Ti–1B and Al–5Zr master alloys on the structural characteristics and tensile properties of Al–12Zn–3 Mg–2.5Cu aluminum alloy. The optimum amount for Ti and Zr containing master alloys was selected as 1 wt.% and 6 wt.%, respectively. The results also showed that Ti containing master alloy is more effective in reducing average grain size of the alloy. T6 heat treatment was applied for all specimens before tensile testing. In heat treated condition, the average tensile strength of 505 MPa was found to be increased to 621 MPa for sample refined with 1 wt.% Al–5Ti–1B (0.05 wt.% Ti). SEM fractography of the fractured faces of several castings showed an overall macroscopically brittle appearance at low magnifications. At higher magnifications, unrefined specimens showed cracking along the grains, whereas Ti-refined specimens showed cracks in individual intermetallic compounds.     

Optical and electrical properties of soluble copolymers of pyrrole-thiophene-3-decylthiophene

Three novel soluble copolymers of pyrrole(P)-thiophene(T)-3-decylthiophene (D) at different molar ratio of comonomers 4 : 1 : 5, 1 : 4 : 5 and 1 : 1 : 2 have been synthesized. NMR, FTIR, UV, emission spectroscopy, GPC, DSC, TGA and conductivity measurements were used to characterize these copolymers. The dark electrical conductivity increases from 3–7 × 10^–6 S/m for undoped samples to 10^–1–10^–2 S/m for samples doped with 4% of iodine, and to 10–10² S/m for 16% of iodine in a form of I₃ ^–.     

Epitaxial growth of Cu6Sn5 formed at Sn-based lead-free solder/non-textured polycrystalline Cu plate interface

This study examines the epitaxial growth of the intermetallic compound (IMC) of Cu₆Sn₅ (or (Cu,Ni)₆Sn₅) that forms at the interface between molten Sn-based lead-free solders and non-textured polycrystalline Cu substrates. Sn, Sn–Cu, Sn–Cu–Ni and Sn–Ag–Cu solders were investigated. The dominant growing planes in a hexagonal structure of this IMC on Cu substrates are (101) and (102). Addition of trace Ni into Sn–Cu solders leads to an increase in (101) growth and a decrease in (102) growth. The presence of Ag in Sn–Ag–Cu solders facilitates (102) growth and suppresses (101) growth. Such an epitaxial growth should have a large influence on the mechanical and electrical characteristics of the Sn-based solder/Cu joints.     

Hydroerosion of steel in alkaline media

The article describes the results of a study of the resistance of St.45 and Cr18Ni10Ti steels to hydroerosion in sodium hydroxide solutions with pH=8–13 and in limewater with ph=11.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 5, No. 5, pp. 584–587, September–October, 1969.     

TEM analysis of tweed structure in high-palladium dental alloys

Transmission electron microscopy and convergent-beam electron diffraction were used to study three high-palladium dental alloys: an as-cast Pd–Ga alloy, a cast Pd–Cu–Ga alloy aged at room temperature for over 5 years, and a cast Pd–Cu–Ga alloy annealed at 1023 K for 2 h and slowly cooled to room temperature. Bands containing a tweed structure in the Pd-Ga alloy were 120° twins with (1 ¯1 0 mirror planes. Within these bands the alloy had a face-centered tetragonal structure with a c/a ratio of 1.03. The aged Pd–Cu–Ga alloy contained a larger amount of tweed structure than the original as-cast alloy, along with randomly oriented bands and thin lath-like regions. The annealed Pd–Cu–Ga alloy contained rectangular particles of a secondary phase that may be Pd₂Ga, Pd₅Ga₂ or Pd₁₃Ga₅. The microtwinned band structure relieves the strain energy arising from transformation of the f.c.c. palladium solid solution on cooling. © 1999 Kluwer Academic Publishers     

The Activity of the Components of a Na–K–Cs System at High Temperatures

The activity coefficients of the components of a Na–K–Cs ternary system in a temperature range of 773–1200 K are determined using the previously calculated thermodynamic properties, in particular, the activity of the components of binary alloys of alkali metals such as Na–K, Na-Cs, and K–Cs, at high temperatures [1–3]. The sides of the triangle of the phase diagram of this system are constituted by the binary Na–K, Na–Cs, and K–Cs binary alloys. The results obtained are used to calculate the saturated vapor pressure of the sodium–potassium-cesium eutectic (22.1 wt % K and 73.8 wt % Cs [4, 5]) in the same temperature range. The calculated data are in good agreement with the recommended reference data [6].     

Effect of rapid solidification on the microstructure and mechanical properties of hot-pressed Al–20Si–5Fe alloys

The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al–20Si–5Fe–2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 × 10⁵ K/s and 5 × 10⁷ K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 °C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated. Results showed a profound effect of the cooling rate, consolidation stage, and transition metals on the microstructure and mechanical strength of Al–20Si–5Fe alloys. While microstructural refining was obtained at both cooling rates, the microstructure of the atomized powder exhibited the formation of fine primary silicon (~ 1 μm), eutectic Al–Si phase with eutectic spacing of ~ 300 nm, and δ-iron intermetallic. Supersaturated Al matrix containing 5–7 at.% silicon and nanometric Si precipitates (20–40 nm) were determined in the microstructure of the melt-spun ribbons. The hot consolidation resulted in coarsening of Si particles in the atomized particles, and precipitation of Si and Fe-containing intermetallics from the supersaturated Al matrix in the ribbons. The consolidated ribbons exhibited higher mechanical strength compared to the atomized powders, particularly at elevated temperatures. The positive influence of the transition metals on the thermal stability of the Al–20Si–5Fe alloy was noticed, particularly in the Ni-containing alloy.     

Low temperature stress relaxation of nanocrystalline nickel

Stress relaxation in nanocrystalline nickel within the temperature range 523–673 K in a uniaxial compression regime is studied in the present investigation. The results obtained for coarser grained nickel are given for comparison. An average strain rate of nanocrystalline nickel within the investigated range of temperatures is 1.75 × 10^–5–3.03 × 10^–5s^–1. The presence of two types of stress relaxation dependencies are shown. The most likely strain mechanism is grain boundary sliding controlled by grain boundary diffusion for temperatures between 623 and 673 K.     

Hygroscopic properties of biological materials and the binding energy of moisture

The binding energy of moisture with biological materials is determined from sorption isotherms for yeast at different temperatures.The work was done in 1992–1993 as a part of a research plan under Grant No. 1392/3-91, financed through the Science Committee of Poland.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 5–6, pp. 461–466, November–December, 1994.     

A certain modification of the fourier hypothesis

We construct impulse solutions for the heat transfer problems.S. V. Starodubtsev Physicotechnical Institute, Tashkent. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 5–6, pp. 500–505, November–December 1994.     

Kinetics of zones of plastic deformation in fatigue failure

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 5, pp. 51–56, September–October, 1992.