Thermophysical Properties of 75Ni–15Mo–10Re Alloy

The true heat capacity, thermal expansion, thermal conductivity, electrical resistance, and density of NMR-75 alloy (75 wt % Ni, 15 wt % Mo, and 10 wt % Re) are investigated in a temperature range of 300–1300 K. The enthalpy, mean coefficient of thermal expansion, thermal diffusivity, and Lorentz number are calculated from the obtained experimental data. The measurement results show that a reversible structural transformation occurs in the alloy in a temperature range of 750–960 K. In accordance with the phase diagram, the ternary system of the alloy consists of an a-solid molybdenum–nickel solution, which is in equilibrium with a -solid rhenium–nickel solution and a Ni₄Mo intermetallic compound. On heating the alloy in a temperature range of 750–960 K, the intermetallic compound transforms into the -solid molybdenum–nickel solution with the absorption of heat, while the ordered structure transforms into a disordered one. The thermal effect Q = 6 kJ/kg and the activation energy of alloy disordering E = 2.2 eV are estimated. The transformation proper is regarded as a second-order transition.     

Hot ductility of wrought 90Cu–10Ni alloy

Abstract

The ductility of a wrought 90Cu–10Ni alloy was investigated by tensile testing over a range of temperatures and for materials of different initial grain sizes. Ductilities were found to vary in a complex manner with temperature and grain size, but at all temperatures above 650 K failure occurred by grain boundary cavitation; good ductilities were associated with either grain boundary migration or recrystallisation during deformation. The microstructures of the deformed specimens were studied using optical microscopy and scanning electron microscopy, and the orientation of cracked boundaries, with respect to the tensile axis, was studied. Analysis of the results indicates that over the temperature range studied more than one cavity growth mechanism was operating. The ductility is discussed in terms of the relationship between the cavity growth mechanisms and restoration processes.

MST/722     

Prediction of the mechanical properties of forged Ti–10V–2Fe–3Al titanium alloy using FNN

In this paper, a fuzzy neural network (FNN) prediction model has been employed to establish the relationship between processing parameters and mechanical properties of Ti–10V–2Fe–3Al titanium alloy. In establishing these relationships, deformation temperature, degree of deformation, solution temperature and aging temperature are entered as input variables while the ultimate tensile strength, yield strength, elongation and area reduction are used as outputs, respectively. After the training process of the network, the accuracy of fuzzy model was tested by the test samples and compared with regression method. The obtained results with fuzzy neural network show that the predicted results are much better agreement with the experimental results than regression method and the maximum relative error is less than 7%. And the optimum matching processing parameters can be quickly selected to achieve the desired mechanical property based on the fuzzy model. It proved that the model has a good precision and excellent ability of predicting.     

Contribution of environment to torsional fatigue behaviour of Cu–10Ni alloy

Abstract

Reverse-torsion fatigue tests on Cu–10Ni alloys containing small quantities of iron in 1 atm gaseous hydrogen, oxygen, and humid air environments, showed that the fatigue life was significantly influenced by the test environment. Multiple crack initiation, crack branching, and changes in fracture mode were observed in the aggressive environments when compared with tests conducted in dry helium. The results are rationalized by a softening mechanism promoted by either hydrogen-assisted overaging or oxidation of the iron particles leading to subsequent decohesion of interfaces in the deformation zones ahead of the crack front.

MST/585     

The effect of alpha phase on flow softening and deformation of Ti–10V–2Fe–3Al

The subtransus deformation behaviour of Ti–10V–2Fe–3Al alloy was investigated. The flow stress curves are featured with significant flow softening, resulting from the breaking up and globularisation of lamellar α phase. The critical major axis of α phase to cause flow softening is 1?µm. Alpha phase acts as a dislocation barrier in the beginning and suppresses the recrystallisation of beta matrix. Dynamic recovery is the main restoration mode for beta matrix and alpha phase just works as a marker of it. Beta phase is dominated by strong {001} and weak {111} orientations. The Burgers relationship and variant selection are observed between α phase and β matrix in a single grain and overall samples, and the subtransus deformation does not destroy it.     

Structure,mechanical properties and grindability of dental Ti–10Zr–X alloys

This study aimed to investigate the structure, mechanical properties and grindability of a binary Ti–Zr alloy added to a series of alloying elements (Nb, Mo, Cr and Fe). The phase and structure of Ti–10Zr–X alloys were evaluated using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. Three-point bending tests were performed using a desk-top mechanical tester. Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m/min). Results were compared with c.p. Ti, which was chosen as a control. Results indicated that the phase/crystal structure, microstructure, mechanical properties and grindability of the Ti–10Zr alloy can be significantly changed by adding small amounts of alloying elements. The alloying elements Nb, Mo, Cr and Fe contributed significantly to increasing the grinding ratio under all grinding conditions, although the grinding rate of all the metals was found to be largely dependent on grinding speed. The Ti–10Zr–1Mo alloy showed increases in microhardness (63%), bending strength (40%), bending modulus (30%) and elastic recovery angle (180%) over those of c.p. Ti, and was also found to have better grindability. The Ti–10Zr–1Mo alloy could therefore be used for prosthetic dental applications if other conditions necessary for dental casting are met.     

Effects of Cr addition on grindability of cast Ti–10Zr based alloys

The present study was undertaken to investigate the microstructure, microhardness and grindability of a series of cast Ti–10Zr–xCr alloys with 1, 3, 5, 7 and 10 wt.% Cr. The grindability of Ti–10Zr and Ti–10Zr–xCr alloys was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m min⁻¹), with the goal of developing a titanium alloy possessing superior grindability than commercially pure titanium (c.p. Ti). The results indicate that the structure of Ti–10Zr–xCr alloys is sensitive to the Cr content. With Cr contents higher than 3 wt.%, the equi-axed β phase began to be retained, while ω phase was found in the Ti–10Zr–3Cr, Ti–10Zr–5Cr and Ti–10Zr–7Cr alloys. The largest quantity of ω phase and the highest microhardness values were found in the Ti–10Zr–5Cr alloy. The grinding rates of the Ti–10Zr based alloys showed a similar tendency to the microhardness. The Ti–10Zr–5Cr alloy exhibited the best grindability, especially at 500, 750 and 1000 m min⁻¹. Its grinding rate at 1000 m min⁻¹ was about 2.6 times that of c.p. Ti, and the grinding ratio was approximately 2.7 times that of c.p. Ti. This study concluded that because Cr can not only harden Titanium, but also improve its grindability, the Ti–10Zr–5Cr alloy has a great potential for use as a dental machining alloy.     

Investigation of serrated flow behaviour in Al–10Mg alloy

Abstract

In view of reported anomalies in the serrated flow behaviour of aged Al–8.6Mg alloy, characteristics of serrated flow were investigated in an Al–10Mg alloy after solution treatment as well as after aging. The material was prepared by melting and casting, and then it was extruded, solution treated, and aged at either 150 or 200°C. Strain rate sensitivity, types of serration, onset strain of serrated flow, magnitude of serrations, and frequency of serrations were studied as a function of aging and strain rate. It was found that the alloy exhibited all the usual features of serrated flow except one, i.e. the magnitude of serration increased in the overaged condition after decreasing up to peak aging.     

Fatigue properties of hot isostatically pressed Al–10Mg castings

Abstract

Constant amplitude fatigue tests have been carried out to assess the effect of hot isostatic pressing (HIP) on the fatigue properties of cast Al–10Mg (wt-%) alloy (AA 520.0). The results showed that HIP treatment can result in large increases in the fatigue life. At a test stress of 106 MN m^?2 (60% of proof stress) the average number of cycles to failure increased by 300% following HIP treatment. The magnitude of the increase was significantly greater at a lower test stress of 84 MN m^?2 (47% of proof stress). However, the scatter in the results from specimens fatigue tested at 106 MN m^?2 following HIP treatment was higher, resulting in a reduction in the safe fatigue life value that could be used for design purposes. Fracture surfaces of these specimens were examined to correlate fatigue life with defect levels. The high scatter can be attributed to the presence of oxide inclusions in the material.

MST/1621     

Low-frequency (10–50 kHz) impedance of polystyrene-onion-like-carbon composites

The impedance of polystyrene-onion-like-carbon (PS-OLC) composites in the low-frequency (10–50 kHz) range has been studied as a function of the OLC weight fraction in the material. The composites were fabricated by rolling of PS filled with OLC powder obtained through the annealing of detonation nanodiamonds at 2140 K. The homogeneity of OLC distribution in the PS matrix has been studied as dependent on the number of rolling stages. It is established that the percolation threshold in PS-OLC composites is achieved at an OLC content of 35–40 wt %.     

Wear behaviour of 85Al–10La–5Ni alloy prepared by powder metallurgy

Abstract

The dry wear behaviour of 85Al–10La–5Ni (at.-%) alloy hot pressed has been studied. The result shows that 85Al–10La–5Ni alloy possessed excellent wear resistance. The wear resistance of the alloy pressed at 773 K is three times as high as that of the A355 aluminium alloy. The fine high hardness intermetallic compounds contribute to the wear resistance of the alloy.     

Influence of sulphur impurity on oxidation behaviour of Ni–10Cr–9Al in air at 1000°C

Abstract

The influence of different amounts of sulphur impurity on the oxidation behaviour of a Ni–10Cr–9Al alloy in air at 1000°C has been investigated. It is indicated by the results that with increasing sulphur content, not only is there a decrease in the scale spalling resistance, but also there is a significant change in the initial growth rate and composition of the scale. Sulphur causes the formation of an inhomogeneous alumina scale by promoting the initial formation of chromia possibly originating from the oxidation of chromium sulphide. It is found that the addition of yttrium is beneficial in reducing both the spalling of the scales and the enhanced scale growth. The influence of the various impurities on the scale spalling characteristics can be correlated with the observed growth mechanisms in the initial stages of oxidation.

MST/929     

Strain rate dependence of the indentation size effect in Ti–10V–2Fe–3Al alloy

The influence of strain rates on the indentation size effect (ISE) was explored experimentally. A strong ISE phenomenon on the hardness of Ti–10V–2Fe–3Al (Ti-1023) alloy was found when the peak-load was less than 3500?mN, regardless of the variation of loading rates. However, as indenter strain rates increased, the degree of ISE reduced considerably, which was related to the decrease of the internal indentation length scale ranging from 23.08 to 6.80?µm. Furthermore, a positive strain rate sensitivity of the hardness in the whole peak-load range was found in Ti-1023 alloy, which showed a linear function of indenter load. The underlying mechanism was well explained by the variation of geometrically necessary dislocation and statistically stored dislocations in Ti-1023 alloy.     

Fatigue behavior and plane-strain fracture toughness of sand-cast Mg–10Gd–3Y–0.5Zr magnesium alloy

In this study, the tensile properties, high cycle fatigue behavior and plane-strain fracture toughness of the sand-cast Mg–10Gd–3Y–0.5Zr magnesium alloy were investigated, comparison to that of sand-cast plus T6 heat treated magnesium alloy which named after sand-cast-T6. The results showed that the tensile properties of the sand-cast alloy are greatly improved after T6 heat treatment, and the fatigue strength (at 10⁷ cycles) of the sand-cast Mg–10Gd–3Y–0.5Zr magnesium alloy increases from 95 to 120 MPa after T6 heat treatment, i.e. the improvement of 26% in fatigue strength has been achieved. The plane-strain fracture toughnesses K_IC of the sand-cast and sand-cast-T6 alloys are about 12.1 and 16.3 MPa m^1/2, respectively. In addition, crack initiation, crack propagation and fracture behavior of the studied alloys after tensile test, high cycle fatigue test and plane-strain fracture toughness test were also investigated systematically.     

Optimization of the properties of 10Sc1CeSZ–NiO composite by the redox treatment

For a 10Sc1CeSZ–NiO porous ceramic composite used as a material of the anode-substrate of a ceramic fuel cell, we propose to perform the redox treatment (cycling) each individual cycle of which includes the reduction of a material at 600°C for 4 h with subsequent stepwise oxidation in air under the same conditions. This enables us to obtain 10Sc1CeSZ–Ni anodic cermet with elevated conductivity despite the lowered content of nickel oxide. Its strength remains on the level of strength of the composite in the initial state.     

Development of corrosion resistant magnesium alloys Part 1 Characterisation of splat quenched Mg–10Al and Mg–16Al alloys

Abstract

The surfaces and bulk of splat quenched Mg–10Al and Mg–16Al (wt-%) alloys were investigated. The surfaces were studied using X-ray photoelectron spectroscopy (XPS) , X-ray excited Auger electron spectroscopy (X-AES), Rutherford backscattering spectrometry (RBS) , scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) and the bulk using X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The solid solubility of Al in Mg was extended to at least 16 wt-%. The quantity of Al ions present on the surfaces of the alloys increased with Al content. Contrary to the suggested layered MgO/Mg–Al–oxide/alloy structure, the surfaces of the alloys consisted of an admixture of magnesium spinel (MgAl₂O₄) in periclase (MgO) and brucite (Mg(OH)₂) of non-uniform thickness varying between 10 and 50 nm, determined via RBS, X-AES, and depth profiling using XPS.

MST/1714a     

Production of a positron beam in the energy range 1–10 MeV

The setup and characteristics of a low energy positron beam at the Giessen linac are desribed. The beam energy can be varied between 1.1 and some MeV. The measured mean positron currents are in the order of some pA within a momentum bin of 0.5%.