Showing papers on "Hardening (metallurgy) published in 1969"
TL;DR: In this article, the authors show that dislocation bundles in dipole and multipole configurations contribute to rapid hardening by providing effective barriers to continued dislocation motion on the primary and secondary slip systems.
139 citations
TL;DR: In this article, a fine grid scribed on the Mg-Al alloy of several grain sizes over a wide range of strain rates was used to measure the contribution of grain strain and the strain associated with grain boundary deformation.
137 citations
TL;DR: In this article, a study of the stress-strain behavior, secondary slip geometry and slip line morphology of niobium single crystals purified by annealing in ultra-high vacuum was made.
Abstract: A study has been made of the stress-strain behaviour, secondary slip geometry and slip line morphology of niobium single crystals purified by annealing in ultra-high vacuum. Within favourable limits of orientation, temperature and strain rate the stress—strain curves exhibit well-defined three-stage hardening. The principal secondary slip system is not usually that bearing the highest proportion of the applied stress and this anomalous behaviour can account for the orientation dependence of overshoot. For temperatures below 250°K the stress-strain curve is non-linear and the initial hardening rate very high. The slip lines observed on crystals deformed at low temperatures belong to a {110} ⟨111⟩ system which, in extreme orientations, is only the sixth most highly stressed system. The slip appears as crystallographic lamellae, in contrast to the wavy slip observed for all other systems.
117 citations
85 citations
TL;DR: In this article, a comprehensive model is proposed to explain the creep of Zircaloy during neutron irradiation, which is based on the growth-directed Roberts-Cottrell yielding creep and the formation of point defect loops preferentially on certain planes in response to the applied stress.
61 citations
TL;DR: In this paper, micro-indentation hardness as a function of composition has been measured for polycrystalline solutions of lead chalcogenide systems and results compared to exsolution tendencies as implied by subsolidus features of the phase diagrams.
Abstract: Vickers micro-indentation hardness as a function of composition has been measured for polycrystalline solutions of lead chalcogenide systems and results compared to exsolution tendencies as implied by subsolidus features of the phase diagrams. Each system exhibited a positive deviation from a linear hardness relation between the end member compounds. The most pronounced hardening was observed for PbS/PbTe solutions; the maximum hardness occurs at about 30 mole % PbTe, coincident with a large solubility gap with a solvus maximum (critical point) at about 30 mol % PbTe and approximately 805° C. The least amount of hardening was observed for the system PbS/PbSe, which exhibits no exsolution at temperatures as low as 300° C. The hardness versus composition curve was approximately symmetric about the 50 mol % composition. Intermediate between these two systems, the PbSe/PbTe crystalline solutions exhibited an asymmetric hardness/composition curve with maximum hardness at about 30 mol % PbTe. Partial phase studies indicate the possibility of a solvus maximum at 500 to 600° C on the PbSe-rich side of the diagram.
54 citations
TL;DR: In this article, the deformation scheme proposed in Part I to account for the multiple linear hardening stage behaviour of long-range ordered iron aluminium alloys has been confirmed by direct transmission electron microscopical observations of superlattice dislocations of the predicted type.
Abstract: The deformation scheme proposed in Part I to account for the multiple linear hardening stage behaviour of long-range ordered iron aluminium alloys has been confirmed by direct transmission electron microscopical observations of superlattice dislocations of the predicted type. Observations of the dislocation sub-structure produced by deformation of single crystals under various conditions are presented, together with a discussion of the properties of said sub-structure and their effect upon the hardening rates of the alloys.
43 citations
TL;DR: In this article, the shape of the stress-temperature (τ vs. T) curve was analyzed according to several expressions discussed in the literature, and a reasonably good fit to the Fleischer expression, ( τ/τ 0 ) 1 2 = 1 − (T/T 0 ), 1 2, was obtained, but an equally good fit was found to the simpler relation (τ/τ0) = 1 + (T0/T).
40 citations
TL;DR: In this paper, the Ni-12 at. % Ti alloy was studied by means of thin foil transmission electron microscopy and electron diffraction technique, which showed two stage age-hardening at 500°C and 600°C.
Abstract: Precipitation behaviour in Ni-12 at. % Ti alloy was studied by means of thin foil transmission electron microscopy and electron diffraction technique. Hardness measurements showed two stage age-hardening at 500°C and 600°C. Thin foil observations revealed that the initial rapid increase in hardness was associated with the presence of superlattice. Slower second hardening was caused by the formation of modulated structure or periodic ordered structure. The increase in hardness by these periodic structures was found to be due to the internal strain hardening as originally suggested by Mott and Nabarro.
37 citations
TL;DR: In this article, the latent hardening in copper aluminium alloys has been investigated as a function of composition and prestrain, and the results are consistent with forest multiplication being inhibited more strongly in the early stages of deformation of alloys than in pure copper.
31 citations
Journal Article•
01 Jan 1969-Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
TL;DR: Stress-strain curves of 150 copper whiskers, whose thickness ranges from 4 to 30µ and growth orientations are parallel to the three principal crystallographic orientations, have been investigated by an Instron-type tensile machine at room temperature as mentioned in this paper.
Abstract: Stress-strain curves of 150 copper whiskers, whose thickness ranges from 4 to 30µ and growth orientations are parallel to the three principal crystallographic orientations, have been investigated by an Instron-type tensile machine at room temperature. Thinner whiskers have shown characteristic sharp yield points. The upper yield stress of some thinner whiskers reaches nearly the theoretical strength of an ideal perfect crystal, but it decreases as the thickness increases. In the subsequent “easy glide” region, corresponding to the propagation of one or a few Luders bands, pronounced serrations appear, and both of flow stress and Luders strain vary approximately in inverse proportion to the thickness. The hardening rate in the most rapid hardening stage of the stress-strain curve increases with increasing thickness. In whiskers, thicker, than about 20µ, the sharp yield point and serrated “easy glide” region are scarcely observable, and their Stress-strain curves are similar to those of bulk crystals.
TL;DR: In this paper, the influence of localized lattice defects on the average dislocation velocity was investigated and it was shown that the effective back stress on a dislocation segment, as it bows out and eventua11y breaks away from local obstacles, is equivalent to a periodic internal stress field.
Abstract: A simple model based on a square array of point obstacles is used to investigate the influence of localized lattice defects on the average dislocation velocity”. It is shown that the effective back stress on a dislocation segment, as it bows out and eventua11y breaks away from local obstacles, is equivalent to a periodic internal stress field. The following types of obstacles are considered. 1. Obstacles that cannot be overcome by thermal activation. These produce a hardening which is practically temperature independent. 2. Obstacles that can be overcome by thermal activation. The influence of this type of obstacle on the average dislocation velocity depends very markedly on the magnitude of both the Peierls friction of the lattice and the interaction energy between the dislocations and the point defects. In crystals with a large Peierls friction the point defects produce a hardening which is proportional to the applied stress and is therefore temperature dependent; however, for large obstacle sp...
TL;DR: In this paper, the hardness of Niobium containing nitrogen and oxygen has been studied by the measurement of hardness at room temperature and three-stage solution hardening has been observed.
Abstract: Solution hardening of niobium by nitrogen and oxygen has been studied by the measurement of hardness at room temperature Three-stage hardening has been observed In Stage I the hardening obeys the 1 2 power law of concentration, whilst in Stages II and III, the power law of one It has been observed that Stage II overlaps about 50% of Stage I It has been confirmed that nitrogen is twice as effective as oxygen in solution hardening, and that grain size has a comparatively small effect on the hardness of electron-beam-refined niobium containing nitrogen and oxygen in solid solution
TL;DR: In this paper, an Fe-0·04 wt.% C alloy was quenched and aged to produce precipitate particles of varying size and spacing, which were fatigued at constant plastic strain over a range of strain amplitudes.
Abstract: An Fe-0·04 wt.% C alloy was quenched and aged to produce precipitate particles of varying size and spacing. Specimens were fatigued at constant plastic strain over a range of strain amplitudes. In the as-quenched condition the alloy exhibited pronounced cyclic hardening which was attributed to strain ageing. The alloy containing fine carbide particles showed high primary cyclic hardening followed by softening. The softening was associated with the formation of precipitate free channels observed by electron microscopy. When larger, more widely spaced noncoherent particles were present in the lattice, primary cyclic hardening was slight even at high strain amplitudes.
TL;DR: In this article, the dependence of the yield stress of vacuum-annealed and hydrogen-purified iron polycrystals on neutron dose and annealing temperature and the influence of these two parameters on the effect of static strain-ageing has been investigated.
Abstract: The dependence of the yield stress of vacuum-annealed and hydrogen-purified iron polycrystals on neutron dose and annealing temperature and the influence of these two parameters on the effect of static strain-ageing has been investigated. The radiation hardening was found to depend sensitively on the interstitial impurities N and C. This may be explained by both a nucleation of precipitation and a trapping of the impurities at radiation produced intrinsic defects. The radiation enhanced precipitation predominates in the relatively impure iron samples at low doses and may be eliminated by annealing at 190 °C. The trapping becomes effective at higher doses or in higher purity iron. Below 400 °C two recovery stages for the yield stress are observed, one between 200 and 260 °C and the other between 320 and 400°C; these may be explained by the detrapping of N and C respectively. The static strain-ageing was found to be reduced by neutron irradiation. It reappears after annealing at temperatures at whi...
TL;DR: In this paper, the authors performed tensile tests on homogenized single crystals of Mg-Sn alloys at room temperature and found that the increase in critical resolved shear stress can be partially explained by short range order (sro).
TL;DR: In this article, a twist compression bonding technique is used to determine the coefficient of adhesion in air for alloys of a variety of compositions from the solid solution systems Cu-Au, Cu-Ni, Au-Ag, Ag-Pd and Pt-Co.
TL;DR: In this article, the authors measured flow stress and optical coloration on a number of MgO single crystals as a function of neutron and electron irradiation and found that the increase in flow stress was proportional to the square root of the concentration of negative-ion vacancies produced by the irradiation.
Abstract: Measurements of the flow stress and optical coloration have been made at room temperature on a number of MgO single crystals as a function of neutron and electron irradiation. The flow stress increase due to electron irradiation is found to be proportional to the square root of the concentration of negative-ion vacancies produced by the irradiation. In the case of neutron irradiation the incremental increase in flow stress is proportional to the square root of the neutron dose. A comparison of these data with hardening due to impurity-vacancy pairs in Fe and Cr-doped MgO indicates that the radiation hardening is due to interstitial type defects.
Patent•
08 Aug 1969TL;DR: In this paper, a dihalogen substituted di- or triazine is added as hardening agent to the casting solution for the photographic layer; casting solution is applied onto the support and the layer is dried.
Abstract: A process for hardening photographic gelatin layers, wherein a dihalogen substituted di- or triazine is added as hardening agent to the casting solution for the photographic layer; the casting solution is applied onto the support and the layer is dried. The drying the performed in effective contact with a water-soluble salt of a primary, secondary or tertiary amine.
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TL;DR: The critical resolved shear stress (C.R.S) for basal slip in single crystals of Mg3Cd has been determined as a function of temperature between 77°K and 500°K as mentioned in this paper.
Abstract: The critical resolved shear stress (C.R.S.S.) for basal slip in single crystals of Mg3Cd has been determined as a function of temperature between 77°K and 500°K. From 77°K to 293°K the crystals were tested in either the ordered or the disordered condition depending upon the prior heat treatment. From 293°K to 500°K the state of order was that in equilibrium at the testing temperature, varying from complete order at the lower temperatures to complete disorder at the higher temperatures. The strain–rate sensitivity of the C.R.S.S. was determined using stress-relaxation tests. The C.R.S.S. of the disordered material between 150°K and 293°K is ascribed to short-range order hardening; the greater C.R.S.S. of the ordered material in the same temperature range is attributed to the immobilization of the screw components of superlattice dislocations by cross-slip onto prism planes. Above 293°K the form of the C.R.S.S. versus temperature curve is attributed to a form of Sumino hardening.
TL;DR: In this paper, the push-pull fatigue behavior of a 355 stainless steel 2024-T8 aluminium alloy composite, at constant stress, has been studied at constant fatigue, and it is inferred that the sequence of failure weakness in the composite is: fibre-matrix interface, matrix and finally, fibres.
Abstract: The push-pull fatigue behaviour of a 355 stainless steel 2024-T8 aluminium alloy composite, has been studied at constant stress. The S-N curve shows a fatigue strength of 20 kg/mm2. Microhardness measurements reveal that little fatigue hardening takes place within the matrix; also, hardness numbers are similar in fatigued specimens, irrespective of the applied stress amplitude. The increase in damping capacity for increasing stress amplitudes, is attributed to increased delamination at the fibre-matrix interface, in the early fatigue stages. This result is also confirmed by optical microscopy. It is inferred that the sequence of failure weakness in the composite is: fibre-matrix interface, matrix and, finally, fibres. A fatigue strength/tensile strength ratio of 0.16 for this material is noticeably low, but fatigue properties of the composite can be improved by enhancing the fibre-matrix bonding.
TL;DR: In this paper, the authors studied the hardening of Ni3(TiAl) alloy with ordered coherent particles, free of interface strains, as a function of γ′ particle size.
TL;DR: In this article, vanadium alloys were examined after 500 and 1500 h exposure to sodium flowing at 5 ft/sec, and showed surface hardness increases due to interstitial absorption, and considerable hardening was observed away from the surface regions.
Abstract: Three vanadium alloys, VANSTAR-7 ∗ , VANSTAR-9, and V-20Ti were examined after 500 and 1500 h exposure to sodium flowing at 5 ft/sec, and containing All alloys showed surface hardness increases due to interstitial absorption, and, in the case of the VANSTAR alloys, considerable hardening was observed away from the surface regions. The bend ductile-brittle transition temperatures were increased after corrosion, and considerable reductions were noted in room-temperature tensile ductility. However, after 1500 h exposure to sodium, samples of the VANSTAR alloys still retained more than adequate ductility at ~700 °C, for cladding applications.
TL;DR: The same character of transformations during hardening by ball burnishing (roller burnishing) and during the running-in period of wear causes the increased wear resistance of ball-burnished surfaces during running in period and the approximately identical wear resistance during the steady wear period for surfaces both hardened and not hardened before wear as discussed by the authors.
Abstract: 1.
During surface hardening by ball burnishing and roller burnishing of gray cast iron microstructural transformations occur in the surface layer-the white phase occurs in treating pearlitic cast iron at low feed rates, the transformation of lamellar pearlite into divorced pearlite, the agglomeration of pearlite and partial transformation of ferrite into pearlite during treatment of pearlitic cast iron with increasing feed rates and during hardening of pearlitic-ferritic cast iron.
2.
Ferritic cast iron is hardened hardly at all but there is danger of re-cold working and “peeling” of the surface layer.
3.
The same character of transformations during hardening by ball burnishing (roller burnishing) and during the running-in period of wear causes the increased wear resistance of ball-burnished surfaces during the running-in period and the approximately identical wear resistance during the steady wear period for surfaces both hardened and not hardened before wear.
TL;DR: In this article, the temperature and strain-rate sensitivities of a polycrystalline high purity Fe-11 at.% Mo alloy, in which the Laves phase Fe2Mo is precipitated on ageing, have been determined in compression in the temperature range 77-550° K for various conditions of ageing.
Patent•
21 Apr 1969
TL;DR: In this paper, the authors describe a SPRING STEEL of stronger resistances to relaxation in service, and show that it is more resistant to stress at a higher temperature than RC 47.
Abstract: COILED STEEL INTERNAL COMBUSTION ENGINE VALVE SPRINGS ARE PRODUCED BY HARDENING CARBON STEEL WIRE, TEMPERING THE HARDENED WIRE TO AN RC HARDNESS OF 50 TO 51 AT ABOUT 700*F., COILING THE TEMPERED WIRE INTO SPRINGS, AND THEN STRESS RELIEVING THE COILED SPRINGS AT A TEMPERATURE ABOVE THE TEMPERING TEMPERATURE AND TO A HARNESS NOT SIGNIFICANTLY GREATER THAN RC 47. THIS RESULTS IN A SPRING STEEL OF DEFINITELY HIGHER RESISTANCE TO RELAXATION IN SERVICE.