Tensile properties of tempered chromium steels in the temperature range 0°to 700°C

Steels containing 0.2 pet C and 0 to 12 pct Cr have been tempered for different times or recrystallized at 700°C and subsequently tensile tested at 100°C temperature intervals in the range 0° to 700°C. At all temperatures, the strength of the as-tempered steels depends primarily on the dislocation structure inherited from the martensite transformation and work softening observed during deformation at 600° and 700° is attributable to recovery of this structure. Strain enhanced precipitation of M₃C is observed after deformation at 200° to 600°C in all the steels, independent of the nature of the carbide present after tempering. Serrated yielding occurs at temperatures increasing from 200° to 400°C with increasing chromium content and is associated with an increase in strength and strain-hardening rate in all cases. It is concluded that dynamic strain-aging results from dislocation locking by chromium-interstitial complexes in the alloy steels. T. Mukherjee, formerly Research Student, Department of Metallurgy, University of Sheffield, Sheffield England. This paper is based upon a thesis submitted by T. Mukherjee in partial fulfillment of the requirements of the degree of Doctor of Philosophy at the University of Sheffield.     

Growth of recrystallised grains in 1.8% Si steel in temperature range 650 to 850°C

Three different types of grain growth were observed: uniform growth producing a regular microstructure; fast individual grain growth and finally a fast secondary recrystallisation initiated by the decarburisation of steel. Uniform growth follows parabolic kinetics. Above appr. 800°C a lower rate of growth is observed than it would be expected by extrapolation from lower temperature. Individual grain growth occurs in areas depleted of cementite and austenite and follows also parabolic kinetics. Nuclea for this type of growth are produced by the coalescence of smaller grains with similar space orientation. An apparent activation energy of 26 kJ/mole was determined for the process of coalescence, while for the uniform growth of recrystallised grains an apparent activation energy of 171 kJ/mole was established. Experimental data show that the texture rich with grains of orientation near to (111) in strips plane results from the greater density of such grains in recrystallised steel and the resulting faster formation of near (111) nuclea of sufficient size suitable for fast growth.     

The constitutive behaviour of a Nb-V HSLA steel in the temperature range of 900 to 975 °C

Isothermal true-stress true-strain flow curves of a Nb-V HSLA steel (0.13% C-1.55% Mn-0.028% Nb-0.059% V) are presented in this paper. Constitutive relations, valid at temperatures from 900 to 975 °C and at rates of strain from 0.005 to 5 s^?1, are derived. It is found that an Arrhenius-type equation, with a digital data bank storing its constants for different levels of normalized strains, represents the material's resistance to deformation adequately.     

Reduktionsgleichgewichte im System Fe–F2O3–CaO oberhalb 1050 °C

Umfangreiche Schrifttumsauswertung der Reduktionsgleichgewichte von Kalkferriten im System Eisen-Hämatit-Calciumoxid und Darstellung der Ergebnisse in Ig (pCO₂/PCO)-1/T-Diagrammen. Unter Verwendung neuester Daten über die Schmelzgleichgewichte des Systems Fe–Fe₂O₃–CaO Extrapolation auf die Reduktionsgleichgewichte des flüssigen Zustandes.     

The time-temperature-transformation diagram within the medium temperature range in some alloy steels

Time-temperature-transformation (TTT) diagrams within the medium temperature range of some alloy steels have usually been found to be composed of three separate kinds of C-curves for low-carbon alloy steels. The microstructure associated with one of three kinds of C-curves is a granular structure which is nonbainite, upper bainite, or lower bainite, depending on the higher, middle, or lower location of the C-curve in the TTT diagrams. On the other hand, only two types of C-curves can be established for the alloy steels of middle and high carbon content, and the category of microstructures (upper bainite and lower bainite) corresponding to each C-curve also depends on the location of the C-curve. Meta-upper bainite, or alternatively, carbide-free bainite, and meta-lower bainite and/or the mixture of them can often be obtained in some alloy steels containing silicon. Each type of microstructure still possesses its own overall transformation activation energy, Q*, and morphological exponent, n. A considerably detailed analysis has suggested some differences among the transformation mechanisms of granular structure, upper bainite, and lower bainite.     

Tensile properties of a 2014 aluminum alloy in the temperature range 250° to 500 °C

The effect of deformation temperature in the range 250° to 500 °C on the tensile ductility of a 2014 aluminum alloy was measured in constant extension-rate tensile tests, generally with an initial strain rate of 2.6 X 10^-3 s^-1. Elongation at fracture increased with increasing temperature in the range 250° to 450 °C, reaching a maximum value of ~180 pct, but in stretching above ~450 °C ductility was reduced by void growth. Below ~350 °C the limiting elongations of solution-treated sheets were much inferior to those of annealed samples. Relatively poor performance in the solution-treated condition was associated with rapid hardening during the first few percent extension followed by overaging at higher strains. When solution-treated sheets were stretched above 400 °C, recovered structures and precipitation on a coarse scale developed at an early stage of straining and the stretching limits were not much inferior to those of annealed sheets at temperatures above 400 °C. The results are discussed in terms of the contributions made to necking resistance by rate-dependent and strain-dependent components of flow strength.     

Das Zustandsschaubild des Systems CaO–FeOn–P2O5–SiO2 bei 1600 °C

Beschreibung eines schematischen Entwurfes für das Zustandsschaubild CaO–FeO_n–P₂O₅–SiO₂. Veränderungen im System CaO–FeO_n–P₂O₅ durch Zusatz von Kieselsäure und im System CaO–FeO_n–SiO₂ durch Zusatz von Phosphorsäure. Ausbildung einer Silikophosphatbarriere. Bedeutung des vorgelegten Entwurfes für phosphatische und silikatische Stahlwerksschlacken.     

Untersuchungen im Schlackensystem Fe–CaO–FeOn–P2O5–SiO2 bei 1600°C

Erläuterungen zur Versuchsdurchführung. Zusammensetzungen der entmischten silikophosphatgesättigten Schlacken auf der phosphorsäure- sowie auf der kalkreichen Seite. Darstellung der Silikophosphatsättigungslinien im Rand-system CaO–P₂O₅–SiO₂ und der Begrenzungslinien der Silikophosphatsättigungsfläche im Vierstoffsystem. Untersuchung der einphasigen silikophosphatgesättigten Schlacken.     

Elevated-pH bioleaching of a low-grade ultramafic nickel sulphide ore in stirred-tank reactors at 5 to 45 °C

This study is a continuation of previous work designed to assess the effect of elevated-pH bioleaching on a low-grade ultramafic nickel sulphide ore from Manitoba, Canada. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as lizardite, making processing of the ore difficult with conventional pyro- and biohydrometallurgical techniques. This work has two objectives: to maximize nickel extraction, and to minimize magnesium mobilization. Five-week stirred-tank bioleaching experiments were conducted with finely ground ore (− 147 µm) at three pH levels (3, 4 and 5) and five temperatures (5, 15, 22.5, 30, and 45 °C). The initial rate of nickel extraction from pentlandite was observed to be inversely correlated to acidity at all temperatures, while the final extraction of nickel after 5 weeks was determined to be moderately correlated to acidity at high temperatures and negatively correlated to acidity at low temperatures. The advantage of elevated-pH bioleaching was most evident at 5 °C, in which the final extraction of nickel at pH 5 was approximately 250% greater than at pH 3. Electron probe X-ray microanalysis of the post-leach residues revealed that the un-reacted lizardite was enriched with nickel during experiments conducted at pH 5, and that the extent of enrichment was a strong function of temperature. The undesirable extraction of magnesium exhibited a strong negative pH–temperature interaction and the consumption of sulphuric acid directly tracked the extraction of magnesium over all experimental conditions. Bioleaching at elevated pH substantially increased the ratio of nickel to magnesium in the leachate, and resulted in a substantial reduction in sulphuric acid consumption.     

Solubility of (MnxFe1-x)S in a 3% Si steel within the temperature range 1100 to 1300°C

By EPMA point counting the contents of sulphur and manganese in solid solution were determined after annealing in a temperature range of 1100 to 1300°C and quenching in three 3% Si steels with 0.055 to 0.38% Mn. The established solubility products are not equal and differ from published data.     

The workability of commercial and experimental 0.6 pct carbon low alloy steels in the temperature range of 650 °C to 870 °C

The torsional strength and ductility of commercial AlSI 4063 steel along with four 0.6 pct carbon, low alloy experimental steel compositions were determined with temperature. These parameters were then related to the workability of the steels. The influence of initial lamellar or spheroidal microstructures, as well as of vacuum or air-melt practices, were studied in the deformation temperature range of 650 °C to 870 °C and strain-rate range of 0.71 to 2.13 s⁻¹ The experimental steels showed increased ductility and lower peak flow stresses over the entire temperature range when compared to the commercial alloy. Lamellar microstructures resulted in higher maximum flow stresses and subsequent work softening in the ferritic regime. Initial carbide morphology did not influence the maximum flow stresses in the austenitic range. Improved ductility of the experimental steels over the entire working temperatures could possibly be attributed to the combination of a reduced amount of oxides and sulfides, reduced particleto-matrix decohesion, improved grain-boundary cohesion, or the ability to annihilate or heal microcracks which may form during deformation. Constitutive equations were developed for the ferritic and austenitic conditions with both spheroidized and lamellar carbides.     

Das Hochofenschlackensystem Al2O3–CaO–MgO–SiO2 bei 1600, 1500 und 1400 °C

Beschreibung von Sättigungsflächen im System Al₂O₃–CaO–MgO–SiO₂ durch isotherme Schnitte im Konzentrationsbereich der Hochofenschlacken für 1600, 1500 und 1400 °C. Räumliche Tetraederdarstellungen und quantitative Grundrißprojektionen nach Überprüfung und Neufestlegung der Grenzflächen des homogenen Schlackenraumes durch Sättigungsschmelzen. Vollständige Darstellung des Grundsystems Al₂O₃–CaO–SiO₂ für 1600, 1500 und 1400 °C. Beispiel für die Anwendung der quantitativen Grundrißprojektion zur Einschätzung der Heterogenität von flüssigen Hochofenschlacken.     

Creep behavior of an Al-2. 0 wt pct Li alloy in the temperature range 300 °C to 500 °C

The elevated temperature deformation behavior of an Al-2. 0 wt pct Li alloy in the temperature range 300 °C to 500 °C was studied using constant extension-rate tension testing and constant true-stress creep testing under both isothermal and temperature cycling conditions. Optical microscopy and transmission electron microscopy (TEM) were employed to assess the effect of deformation on microstructure. The data showed that the stress exponent,n, has a value of about 5. 0 at temperatures above theα +δAlLi solvus (approximately 380 °C) and that subgrains form during plastic deformation. Models for dislocation-climb and dislocation-glide control of creep were analyzed for alloys deformed in the temperature range of stability of the terminal AlLi solid solution. A climb model was shown to describe closely the behavior of this material. Anomalous temperature dependence of the activation energy was observed in this same temperature range. This anomalous behavior was ascribed to unusual temperature dependence of either the Young’s modulus or the stacking fault energy, which may be associated, in turn, with a disorder-order transformation on cooling of the alloy. Formerly with the Materials Engineering Section. Department of Mechanical Engineering, Naval Postgraduate School.     

Errata: The time-temperature-transformation diagram within the medium temperature range in some alloy steels

The online version of the original article can be found at     

Die Gleichgewichte zwischen Eisenschmelzen und Schlacken des Systems FeOn–CaO–P2O5–MgO bei 1600 °C

Entwurf des Schlackensystems FeO_n–CaO–P₂O₅–MgO für 1600 °C aus vorliegenden Schrifttumsangaben. Beschreibung des eigenen Untersuchungsverfahrens zur genaueren Bestimmung des Vierstoffsystems. Versuchsergebnisse zur Bestimmung der Sättigungsflächen des Trikalziumphosphates, des Tetrakalziumphosphates und des Kalkes. Gleichgewichtsphosphorgehalte im Eisenbad unter den Schlacken des untersuchten Vierstoffsystems. Folgerungen für die technische Stahlherstellung.