Abstract Carbon strain-ageing has been studied in a vacuum-melted Fe–0·05% C alloy heat-treated to contain ∼6, 14, and 150 ppm carbon in solution. Damping and electron microscopy were used to follow the progress of ageing at 40° C (313 K) after 10% elongation. The decay of damping during strain-ageing was resolved into two components: Snoek damping and dislocation damping. The decay of Snoek damping obeyed the kinetics predicted by Meisel for segregation of carbon to atmospheres about dislocations. The decay in amplitude-independent dislocation damping followed the damping kinetics predicted by Granato et al. Hence, the decay rates of both types of damping support the theory that carbon atoms migrate to, and pin, dislocations during the initial stage of ageing. Furthermore, the Snoek damping results imply that migration of carbon to dislocations continues long after the dislocations are fully pinned. By transmission electron microscopy, small dark spots were detected in the matrix of highly supersaturated...
{"title":"Kinetics of Damping Decay during Strain-Ageing in an Fe–0.05% C Alloy","authors":"E. C. Oren, E. Stephenson","doi":"10.1179/MSC.1970.4.1.9","DOIUrl":"https://doi.org/10.1179/MSC.1970.4.1.9","url":null,"abstract":"Abstract Carbon strain-ageing has been studied in a vacuum-melted Fe–0·05% C alloy heat-treated to contain ∼6, 14, and 150 ppm carbon in solution. Damping and electron microscopy were used to follow the progress of ageing at 40° C (313 K) after 10% elongation. The decay of damping during strain-ageing was resolved into two components: Snoek damping and dislocation damping. The decay of Snoek damping obeyed the kinetics predicted by Meisel for segregation of carbon to atmospheres about dislocations. The decay in amplitude-independent dislocation damping followed the damping kinetics predicted by Granato et al. Hence, the decay rates of both types of damping support the theory that carbon atoms migrate to, and pin, dislocations during the initial stage of ageing. Furthermore, the Snoek damping results imply that migration of carbon to dislocations continues long after the dislocations are fully pinned. By transmission electron microscopy, small dark spots were detected in the matrix of highly supersaturated...","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"2450 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130950097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/030634568790443387
M. Braunovic, C. W. Haworth, R. T. Weiner
AbstractHardening at the grain boundaries in irons of various purities, and in certain iron-base alloys, has been investigated by means of a microhardness technique. The difference between the grain-boundary and grain-interior hardness values (∆H) increased as the load applied to the indenter was decreased. Zero values of ∆H were found for loads > ∼ 14 g. Factors affecting the grain-boundary hardening were studied: (a) Additions of tungsten or molybdenum reduced the grain-boundary hardness to that of the grain interior at ∼ 0.5 at.-% solute; manganese additions did not affect ∆H (b) Quenching from 900°C eliminated the hardening effect in all the materials investigated. Annealing to equilibrium at temperatures between 300 and ∼ 750°C caused a return of the hardening, the magnitude of which was independent of the annealing temperature. (c) A kinetic study of the rate of recovery of the hardening effect, following quenching from 900°C, showed that it occurs very rapidly. The conditions required for the obser...
{"title":"Grain-Boundary Hardening in Iron and Iron Alloys","authors":"M. Braunovic, C. W. Haworth, R. T. Weiner","doi":"10.1179/030634568790443387","DOIUrl":"https://doi.org/10.1179/030634568790443387","url":null,"abstract":"AbstractHardening at the grain boundaries in irons of various purities, and in certain iron-base alloys, has been investigated by means of a microhardness technique. The difference between the grain-boundary and grain-interior hardness values (∆H) increased as the load applied to the indenter was decreased. Zero values of ∆H were found for loads > ∼ 14 g. Factors affecting the grain-boundary hardening were studied: (a) Additions of tungsten or molybdenum reduced the grain-boundary hardness to that of the grain interior at ∼ 0.5 at.-% solute; manganese additions did not affect ∆H (b) Quenching from 900°C eliminated the hardening effect in all the materials investigated. Annealing to equilibrium at temperatures between 300 and ∼ 750°C caused a return of the hardening, the magnitude of which was independent of the annealing temperature. (c) A kinetic study of the rate of recovery of the hardening effect, following quenching from 900°C, showed that it occurs very rapidly. The conditions required for the obser...","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130975889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/030634572790445803
H. Fischmeister, E. Navara, K. Easterling
Abstract The effect of dispersed oxide particles on the mechanical and high-temperature properties of a composite is closely related to their cohesion with the matrix and to their stability at elevated temperatures. Both these properties are affected by solutes in the matrix and the effect can be positive or negative in either case. The stability of the dispersion is reflected by its resistance to coarsening by Ostwald ripening. The coarsening rate is governed by several factors, most of which are affected by alloying additives in the matrix. The nature of this influence is discussed on the basis of results obtained on composites of alumina in matrices of nickel, iron, and iron–40% nickel with various minor alloying additions. Particle/matrix bonding is largely dependent on the magnitude of the interfacial energy between the oxide and the metal, which in turn is dependent on matrix alloying. The work of adhesion between matrix and particles has been determined by measuring contact angles at strain-induced...
{"title":"Effects of Alloying on Structural Stability and Cohesion between Phases in Oxide/Metal Composites","authors":"H. Fischmeister, E. Navara, K. Easterling","doi":"10.1179/030634572790445803","DOIUrl":"https://doi.org/10.1179/030634572790445803","url":null,"abstract":"Abstract The effect of dispersed oxide particles on the mechanical and high-temperature properties of a composite is closely related to their cohesion with the matrix and to their stability at elevated temperatures. Both these properties are affected by solutes in the matrix and the effect can be positive or negative in either case. The stability of the dispersion is reflected by its resistance to coarsening by Ostwald ripening. The coarsening rate is governed by several factors, most of which are affected by alloying additives in the matrix. The nature of this influence is discussed on the basis of results obtained on composites of alumina in matrices of nickel, iron, and iron–40% nickel with various minor alloying additions. Particle/matrix bonding is largely dependent on the magnitude of the interfacial energy between the oxide and the metal, which in turn is dependent on matrix alloying. The work of adhesion between matrix and particles has been determined by measuring contact angles at strain-induced...","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127842715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/030634573790445497
R. Priestner, M. S. Biring
AbstractThe effects have been measured of tensile strains of < 0.21 at 950° C on the transformation of three low-carbon steel austenites. Hot deformation of 0.1% C and of 0.1 C, 1.5 Mn, 0.04% Nb steels austenitized at 950° C hastened their transformation to ferrite and softened the transformation product. In the niobium steel austenitized at a high temperature to dissolve NbC and coarsen the grain size before testing at 950° C, deformation also accelerated transformation to ferrite, but without affecting the strength. In these steels transformation to ferrite occurred before the deformed austenites recrystallized. In 0.1 C, 1.5% Mn steel transformation was slow enough for austenite deformed to a strain of 0.21 to recrystallize before transformation, which retarded transformation to ferrite; only at a smaller strain of 0.105 was transformation of this austenite accelerated. These direct effects of hot deformation do not account for the improved strength and toughness of control-rolled low-carbon steels.
{"title":"Transformation of Low-Carbon Austenite after Small Plastic Strains","authors":"R. Priestner, M. S. Biring","doi":"10.1179/030634573790445497","DOIUrl":"https://doi.org/10.1179/030634573790445497","url":null,"abstract":"AbstractThe effects have been measured of tensile strains of < 0.21 at 950° C on the transformation of three low-carbon steel austenites. Hot deformation of 0.1% C and of 0.1 C, 1.5 Mn, 0.04% Nb steels austenitized at 950° C hastened their transformation to ferrite and softened the transformation product. In the niobium steel austenitized at a high temperature to dissolve NbC and coarsen the grain size before testing at 950° C, deformation also accelerated transformation to ferrite, but without affecting the strength. In these steels transformation to ferrite occurred before the deformed austenites recrystallized. In 0.1 C, 1.5% Mn steel transformation was slow enough for austenite deformed to a strain of 0.21 to recrystallize before transformation, which retarded transformation to ferrite; only at a smaller strain of 0.105 was transformation of this austenite accelerated. These direct effects of hot deformation do not account for the improved strength and toughness of control-rolled low-carbon steels.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126763026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/MSC.1970.4.1.215
B. Burton, G. W. Greenwood
AbstractExperiments are described on the deformation of copper, both in the form of long straight wires and in the form of helices, with the aim of evaluating the importance of diffusion-creep processes, especially in the range where the effect of grain-boundary diffusion is expected to predominate. It is established that at low stresses and elevated temperatures, polycrystalline copper can behave in a Newtonian manner with the primary creep stage of negligible importance. Above a specific temperature, which is shown to vary inversely as the logarithm of the grain size, creep rates agree closely with the Nabarro–Herring equation, and the activation energy is identical with that for lattice self-diffusion. Below this temperature the activation energy is found to be near the value expected for grain-boundary self-diffusion, and the creep rate now varies inversely as the cube of the grain size in agreement with the equation derived by Coble (J. Applied Physics, 1963, 34, 1679). Within the range of the presen...
{"title":"The Contribution of Grain-Boundary Diffusion to Creep at Low Stresses","authors":"B. Burton, G. W. Greenwood","doi":"10.1179/MSC.1970.4.1.215","DOIUrl":"https://doi.org/10.1179/MSC.1970.4.1.215","url":null,"abstract":"AbstractExperiments are described on the deformation of copper, both in the form of long straight wires and in the form of helices, with the aim of evaluating the importance of diffusion-creep processes, especially in the range where the effect of grain-boundary diffusion is expected to predominate. It is established that at low stresses and elevated temperatures, polycrystalline copper can behave in a Newtonian manner with the primary creep stage of negligible importance. Above a specific temperature, which is shown to vary inversely as the logarithm of the grain size, creep rates agree closely with the Nabarro–Herring equation, and the activation energy is identical with that for lattice self-diffusion. Below this temperature the activation energy is found to be near the value expected for grain-boundary self-diffusion, and the creep rate now varies inversely as the cube of the grain size in agreement with the equation derived by Coble (J. Applied Physics, 1963, 34, 1679). Within the range of the presen...","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123017717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/030634572790445867
J. Hancock, I. Dillamore, R. Smallman
AbstractThe creep behaviour of three Ni–Co–2.5% A12O3 alloys containing 0, 30) and 67% Co has been studied at temperatures in the region of 770 and 1000 K. It is shown that in both ranges the steady-state creep rate depends upon stress to the power four. At the lower temperature the activation energy is composition-dependent, values of 85, 184, and 121 kJ/mol being recorded for the 0, 30, and 67% Co alloys, respectively. At the higher temperature the activation energy corresponds with that for self-diffusion and, like the pre-exponential term, is essentially independent of composition except through small variations in diffusivity. The low-temperature creep is explained in terms of a thermally activated cross-slip and pipe-diffusion mechanism that enables dislocations to by-pass particles. At the higher temperature it is suggested that bulk diffusion is the rate-controlling process and that the absence of any marked composition-dependence is due to the jog distribution being determined mainly by dislocati...
{"title":"The Creep of Dispersion-Strengthened Ni–Co Alloys","authors":"J. Hancock, I. Dillamore, R. Smallman","doi":"10.1179/030634572790445867","DOIUrl":"https://doi.org/10.1179/030634572790445867","url":null,"abstract":"AbstractThe creep behaviour of three Ni–Co–2.5% A12O3 alloys containing 0, 30) and 67% Co has been studied at temperatures in the region of 770 and 1000 K. It is shown that in both ranges the steady-state creep rate depends upon stress to the power four. At the lower temperature the activation energy is composition-dependent, values of 85, 184, and 121 kJ/mol being recorded for the 0, 30, and 67% Co alloys, respectively. At the higher temperature the activation energy corresponds with that for self-diffusion and, like the pre-exponential term, is essentially independent of composition except through small variations in diffusivity. The low-temperature creep is explained in terms of a thermally activated cross-slip and pipe-diffusion mechanism that enables dislocations to by-pass particles. At the higher temperature it is suggested that bulk diffusion is the rate-controlling process and that the absence of any marked composition-dependence is due to the jog distribution being determined mainly by dislocati...","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126330254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
AbstractDamping tests at 1 c/s and dilatometric measurements of the α–γ transition temperature have been carried out on high-purity iron (99·9985%) and its dilute alloys with boron. Confirmation has been obtained of the hypothesis previously advanced that boron does not dissolve interstitially in alpha-iron when the metal is very pure and, more generally, that the available data for boron solubility are dependent on the content of impurities in the iron used.
{"title":"On the Solubility of Boron in High-Purity Alpha-Iron","authors":"A. Lucci, G. Gatta, G. Venturello","doi":"10.1179/MSC.1969.3.1.14","DOIUrl":"https://doi.org/10.1179/MSC.1969.3.1.14","url":null,"abstract":"AbstractDamping tests at 1 c/s and dilatometric measurements of the α–γ transition temperature have been carried out on high-purity iron (99·9985%) and its dilute alloys with boron. Confirmation has been obtained of the hypothesis previously advanced that boron does not dissolve interstitially in alpha-iron when the metal is very pure and, more generally, that the available data for boron solubility are dependent on the content of impurities in the iron used.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125914258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/030634568790511534
I. F. Hughes, B. L. Daniell
AbstractTransient damping in equiaxed and irregular ferrite in high-purity iron after 2½ and 5% strain has been investigated, using a low-frequency torsion pendulum. Recovery can be fitted to an equation of the type P = exp (− Btn), where n varies between 0.15 and 0.45. The activation energy for recovery is between 8.5 and 10.5 kcal/mole. It is suggested that the mechanism of recovery is associated with the rearrangement of dislocations.
{"title":"Transient Damping in Equiaxed and Irregular Ferrite","authors":"I. F. Hughes, B. L. Daniell","doi":"10.1179/030634568790511534","DOIUrl":"https://doi.org/10.1179/030634568790511534","url":null,"abstract":"AbstractTransient damping in equiaxed and irregular ferrite in high-purity iron after 2½ and 5% strain has been investigated, using a low-frequency torsion pendulum. Recovery can be fitted to an equation of the type P = exp (− Btn), where n varies between 0.15 and 0.45. The activation energy for recovery is between 8.5 and 10.5 kcal/mole. It is suggested that the mechanism of recovery is associated with the rearrangement of dislocations.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"187 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114182726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/030634570790444103
Y. Prasad, D. Sastry, K. Vasu
AbstractLow-temperature creep in aluminium has been studied by means of change-in-stress experiments. The value of the flow parameter B (= ∆ ln έ/∆τ) was higher for creep following stress decrements than that for creep following increments, the difference being negligible at higher stresses. Among the various possible mechanisms considered, a model based on the formation of attractive junctions following a stress decrement, causing a change in the number of dislocation elements participating in the activation event, explains the effect satisfactorily.
{"title":"A Study of Low-Temperature Creep in Aluminium by Change-in-Stress Experiments: Thermal Activation of Attractive Junctions","authors":"Y. Prasad, D. Sastry, K. Vasu","doi":"10.1179/030634570790444103","DOIUrl":"https://doi.org/10.1179/030634570790444103","url":null,"abstract":"AbstractLow-temperature creep in aluminium has been studied by means of change-in-stress experiments. The value of the flow parameter B (= ∆ ln έ/∆τ) was higher for creep following stress decrements than that for creep following increments, the difference being negligible at higher stresses. Among the various possible mechanisms considered, a model based on the formation of attractive junctions following a stress decrement, causing a change in the number of dislocation elements participating in the activation event, explains the effect satisfactorily.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121850701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1900-01-01DOI: 10.1179/MSC.1969.3.1.209
F. R. Coe, J. Moreton
AbstractClassical reaction kinetics has been employed to describe the movement of hydrogen in ferritic steels in the range 100–350° C. Predictions based on theory are supported by the results of experiments on three materials. The two processes of lattice diffusion of hydrogen and the release of hydrogen from traps in the metal are combined as consecutive reactions, the former being the rate-controlling step at high temperatures and the latter at low temperatures. In the intermediate region where neither process is predominant, there will be a gradual transition from one mode of reaction to another. Values for both the true lattice and the overall diffusivity coefficients are calculated in the intermediate-temperature region. It is shown that a practical implication of this theory is that it is necessary to select higher temperatures or longer times for post-heat-treatments for wrought steels and weldments in the intermediate-temperature region than had previously been anticipated.
{"title":"A Kinetic Approach to Hydrogen Diffusion through Steel at 100–350°C","authors":"F. R. Coe, J. Moreton","doi":"10.1179/MSC.1969.3.1.209","DOIUrl":"https://doi.org/10.1179/MSC.1969.3.1.209","url":null,"abstract":"AbstractClassical reaction kinetics has been employed to describe the movement of hydrogen in ferritic steels in the range 100–350° C. Predictions based on theory are supported by the results of experiments on three materials. The two processes of lattice diffusion of hydrogen and the release of hydrogen from traps in the metal are combined as consecutive reactions, the former being the rate-controlling step at high temperatures and the latter at low temperatures. In the intermediate region where neither process is predominant, there will be a gradual transition from one mode of reaction to another. Values for both the true lattice and the overall diffusivity coefficients are calculated in the intermediate-temperature region. It is shown that a practical implication of this theory is that it is necessary to select higher temperatures or longer times for post-heat-treatments for wrought steels and weldments in the intermediate-temperature region than had previously been anticipated.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114045260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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