Pub Date : 1900-01-01DOI: 10.1179/MSC.1970.4.1.130
K. Easterling, A. Thölén
Abstract Hot-stage electron microscopy has been used to study the sintering of b.c.c. (Fe) and f.c.c. (Fe–Ni) powders in the size range 0·005–0·2 μm, where the particles are transparent to 100 kV electrons. The observations show that in the absence of an external load dislocations play no part in sintering, even in the earliest stages of neck growth. The sphere–sphere model is employed to calculate the total climbing forces (elastic plus chemical) acting on dislocations, and elasticity theory is applied to determine the principal and maximum shear stresses generated at the weld-neck of sintering particles. Only dislocations lying very close to the grain boundary can move to the neck or the grain boundary and so contribute to neck growth. However, the maximum shear stresses generated in sintering are too small to nucleate new dislocations and it is thus concluded that neck growth is controlled solely by diffusional processes.
{"title":"A Study of Sintering Using Hot-Stage Electron Microscopy","authors":"K. Easterling, A. Thölén","doi":"10.1179/MSC.1970.4.1.130","DOIUrl":"https://doi.org/10.1179/MSC.1970.4.1.130","url":null,"abstract":"Abstract Hot-stage electron microscopy has been used to study the sintering of b.c.c. (Fe) and f.c.c. (Fe–Ni) powders in the size range 0·005–0·2 μm, where the particles are transparent to 100 kV electrons. The observations show that in the absence of an external load dislocations play no part in sintering, even in the earliest stages of neck growth. The sphere–sphere model is employed to calculate the total climbing forces (elastic plus chemical) acting on dislocations, and elasticity theory is applied to determine the principal and maximum shear stresses generated at the weld-neck of sintering particles. Only dislocations lying very close to the grain boundary can move to the neck or the grain boundary and so contribute to neck growth. However, the maximum shear stresses generated in sintering are too small to nucleate new dislocations and it is thus concluded that neck growth is controlled solely by diffusional processes.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"136 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":"115884211","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: 10.1179/030634568790443341
A. Davenport, F. G. Berry, R. Honeycombe
AbstractDuring the decomposition of austenite to ferrite in certain iron-base alloys a new form of precipitation has been observed at the ferrite/austenite interface. In appropriate alloys, V4C3, Mo2C, and Cr7C3 form very fine particles on the interface, which repeatedly moves on to provide fresh sites for further nucleation. The transformation leads to a very fine banded dispersion of carbide in ferrite having striking morphological differences from the same carbides in tempered martensite.
{"title":"Interphase Precipitation in Iron Alloys","authors":"A. Davenport, F. G. Berry, R. Honeycombe","doi":"10.1179/030634568790443341","DOIUrl":"https://doi.org/10.1179/030634568790443341","url":null,"abstract":"AbstractDuring the decomposition of austenite to ferrite in certain iron-base alloys a new form of precipitation has been observed at the ferrite/austenite interface. In appropriate alloys, V4C3, Mo2C, and Cr7C3 form very fine particles on the interface, which repeatedly moves on to provide fresh sites for further nucleation. The transformation leads to a very fine banded dispersion of carbide in ferrite having striking morphological differences from the same carbides in tempered martensite.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"272 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":"115890191","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: 10.1179/030634573790445389
R. C. Gifkins
AbstractThe various methods of measuring grain-boundary sliding are reviewed, critical attention being given to consideration of their rigour and practicability; they include surface and interior marker lines, surface steps, and the analysis of change in grain shape. A new suggestion is put forward to explain differences between estimates of the contribution of sliding to the overall extension made from measurements on the surface and in the interior.
{"title":"The Measurement of Grain-Boundary Sliding in Polycrystalline Specimens","authors":"R. C. Gifkins","doi":"10.1179/030634573790445389","DOIUrl":"https://doi.org/10.1179/030634573790445389","url":null,"abstract":"AbstractThe various methods of measuring grain-boundary sliding are reviewed, critical attention being given to consideration of their rigour and practicability; they include surface and interior marker lines, surface steps, and the analysis of change in grain shape. A new suggestion is put forward to explain differences between estimates of the contribution of sliding to the overall extension made from measurements on the surface and in the interior.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"7 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":"131380749","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.1967.1.1.119
E. Smith
AbstractThis paper presents two approaches to the problem of cleavage-crack nucleation by a pile-up of screw dislocations. The results obtained by a simple approximate procedure, similar in principle to that employed in a previous paper (Metal Sci. J., 1967, 1, 56) for the corresponding edge-dislocation problem, are compared with those determined by an exact approach made possible because of the special characteristics of screw dislocations. There is very good agreement between the two sets of results, indicating that the earlier results for nucleation at edge-dislocation pile-ups approximate very closely to the real state of affairs.
{"title":"Nucleation of Cleavage Cracks in Crystalline Solids: Fracture at Screw-Dislocation Pile-Ups","authors":"E. Smith","doi":"10.1179/MSC.1967.1.1.119","DOIUrl":"https://doi.org/10.1179/MSC.1967.1.1.119","url":null,"abstract":"AbstractThis paper presents two approaches to the problem of cleavage-crack nucleation by a pile-up of screw dislocations. The results obtained by a simple approximate procedure, similar in principle to that employed in a previous paper (Metal Sci. J., 1967, 1, 56) for the corresponding edge-dislocation problem, are compared with those determined by an exact approach made possible because of the special characteristics of screw dislocations. There is very good agreement between the two sets of results, indicating that the earlier results for nucleation at edge-dislocation pile-ups approximate very closely to the real state of affairs.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"19 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":"130051676","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: 10.1179/030634572790446172
T. Gibbons
AbstractZones free of γ′ precipitate formed adjacent to grain boundaries in the gauge-lengths of specimens of Ni–20 % Cr-base alloys subjected to creep tests or slow-strain-rate tensile tests in the temperature range 750–850°C (1023–1123 K) have been studied. Electron-probe microanalysis did not reveal any significant change in composition between the precipitate-free zones and the grain interior. Consideration of the variation in the stress-dependence of minimum creep rate with temperature and grain size indicates that a diffusion creep mechanism may explain the formation of the precipitate-free zones.
{"title":"The Influence of Diffusion Creep on Precipitate-Free Zone Formation in Ni–20% Cr-Base Alloys","authors":"T. Gibbons","doi":"10.1179/030634572790446172","DOIUrl":"https://doi.org/10.1179/030634572790446172","url":null,"abstract":"AbstractZones free of γ′ precipitate formed adjacent to grain boundaries in the gauge-lengths of specimens of Ni–20 % Cr-base alloys subjected to creep tests or slow-strain-rate tensile tests in the temperature range 750–850°C (1023–1123 K) have been studied. Electron-probe microanalysis did not reveal any significant change in composition between the precipitate-free zones and the grain interior. Consideration of the variation in the stress-dependence of minimum creep rate with temperature and grain size indicates that a diffusion creep mechanism may explain the formation of the precipitate-free zones.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"87 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":"130120788","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: 10.1179/030634573790445712
E. Furubayashi, H. Yoshida, H. Endo
AbstractThe precipitation behaviour in a solution-treated and 5% deformed Fe-0.04% Al-0.005% N alloy has been studied at elevated temperatures by means of in situ observation of the foils in a high-voltage electron microscope. The operating voltages selected were 400 and 500 kV, which are, respectively, below and above the threshold voltage for the formation of Frenkel defects in α-Fe. Precipitates seen at the beginning of the heating experiment consisted of α″-Fe16N2 and were found to be much finer in deformed specimens than in undeformed ones. Following the reversion of α″ at ∼ 150° C, AlN precipitates were present in the temperature range between 520 and 560° C under irradiating conditions with 500 kV electrons, while under non-irradiating conditions they were observed above 7000° C. Prismatic dislocation loops induced by deformation were found to be preferred nucleation sites for the precipitation of both α″ and AlN.
{"title":"Electron-Microscope Study of Precipitation Sites in a Deformed Fe-Al-N Alloy","authors":"E. Furubayashi, H. Yoshida, H. Endo","doi":"10.1179/030634573790445712","DOIUrl":"https://doi.org/10.1179/030634573790445712","url":null,"abstract":"AbstractThe precipitation behaviour in a solution-treated and 5% deformed Fe-0.04% Al-0.005% N alloy has been studied at elevated temperatures by means of in situ observation of the foils in a high-voltage electron microscope. The operating voltages selected were 400 and 500 kV, which are, respectively, below and above the threshold voltage for the formation of Frenkel defects in α-Fe. Precipitates seen at the beginning of the heating experiment consisted of α″-Fe16N2 and were found to be much finer in deformed specimens than in undeformed ones. Following the reversion of α″ at ∼ 150° C, AlN precipitates were present in the temperature range between 520 and 560° C under irradiating conditions with 500 kV electrons, while under non-irradiating conditions they were observed above 7000° C. Prismatic dislocation loops induced by deformation were found to be preferred nucleation sites for the precipitation of both α″ and AlN.","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":"132865278","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: 10.1179/030634568790443116
P. Bowring, P. W. Davies, B. Wilshire
AbstractDensity measurements have been carried out after creep of a nickel-0.1 at.-% palladium alloy and Magnox AL80. The continuous decrease in density that occurs during the creep life was found to be linearly related to the strain throughout the later stages of creep. With the nickel alloy this linear relationship applied to all strains after the end of primary creep, but with Magnox AL80 linearity was not observed until later in the creep life. The variation in this initial period is shown to account for differences in the time-dependence of cavity growth observed with these materials.
{"title":"The Strain-Dependence of Density Changes during Creep","authors":"P. Bowring, P. W. Davies, B. Wilshire","doi":"10.1179/030634568790443116","DOIUrl":"https://doi.org/10.1179/030634568790443116","url":null,"abstract":"AbstractDensity measurements have been carried out after creep of a nickel-0.1 at.-% palladium alloy and Magnox AL80. The continuous decrease in density that occurs during the creep life was found to be linearly related to the strain throughout the later stages of creep. With the nickel alloy this linear relationship applied to all strains after the end of primary creep, but with Magnox AL80 linearity was not observed until later in the creep life. The variation in this initial period is shown to account for differences in the time-dependence of cavity growth observed with these materials.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"11 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":"132906853","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: 10.1179/030634573790445505
W. Hutchinson, B. A. Wilcox
Abstract Preferred orientation has been examined in extruded, drawn, and swaged nickel, nickel-20% chromium, and nickel-20% chromium-l0% tungsten, with and without a dispersion of 2 vol.-% of thoria particles. Duplex 〈100〉 + 〈111〉 fibre textures were observed in most cases. The 〈100〉 component was stabilized by the presence of particles and also by the application of intermediate anneals during deformation. These results and the stability of the deformed state in thoriated nickel are attributed largely to the action of the particles in generating homogeneous deformation.
{"title":"The Influence of a Thoria Dispersion on Preferred Orientation in Nickel Alloys","authors":"W. Hutchinson, B. A. Wilcox","doi":"10.1179/030634573790445505","DOIUrl":"https://doi.org/10.1179/030634573790445505","url":null,"abstract":"Abstract Preferred orientation has been examined in extruded, drawn, and swaged nickel, nickel-20% chromium, and nickel-20% chromium-l0% tungsten, with and without a dispersion of 2 vol.-% of thoria particles. Duplex 〈100〉 + 〈111〉 fibre textures were observed in most cases. The 〈100〉 component was stabilized by the presence of particles and also by the application of intermediate anneals during deformation. These results and the stability of the deformed state in thoriated nickel are attributed largely to the action of the particles in generating homogeneous deformation.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"12 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":"133431184","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: 10.1179/030634570790444211
M. Murphy, G. D. Branch
AbstractOur attention has been drawn to a recent paper by Boniszewski and Eaton in which reference is made to our work on 12% CrMoVNb steels. They have made a valuable contribution to the problem of reheat cracking in CrMoV steels but we feel that their understanding of creep-rupture ductility would be enhanced if they gave more consideration to the time variable.
{"title":"Electron Fractography of Weld-Reheat Cracking in CrMoV Steel","authors":"M. Murphy, G. D. Branch","doi":"10.1179/030634570790444211","DOIUrl":"https://doi.org/10.1179/030634570790444211","url":null,"abstract":"AbstractOur attention has been drawn to a recent paper by Boniszewski and Eaton in which reference is made to our work on 12% CrMoVNb steels. They have made a valuable contribution to the problem of reheat cracking in CrMoV steels but we feel that their understanding of creep-rupture ductility would be enhanced if they gave more consideration to the time variable.","PeriodicalId":103313,"journal":{"name":"Metal Science Journal","volume":"78 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132273432","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: 10.1179/030634570790444239
K. Thommen
Abstract An analytical expression has been derived for the number of vacancy–vacancy bonds of large spherical vacancy clusters in a rigid f.c.c. lattice. This permits the relation of the surface-energy density of large spherical voids to the vacancy-formation energy for f.c.c. metals with very-short-range interatomic interaction.
{"title":"Surface-Energy Density of Large Spherical Voids in F.C.C. Lattices","authors":"K. Thommen","doi":"10.1179/030634570790444239","DOIUrl":"https://doi.org/10.1179/030634570790444239","url":null,"abstract":"Abstract An analytical expression has been derived for the number of vacancy–vacancy bonds of large spherical vacancy clusters in a rigid f.c.c. lattice. This permits the relation of the surface-energy density of large spherical voids to the vacancy-formation energy for f.c.c. metals with very-short-range interatomic interaction.","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":"132374741","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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