摘要:

AbstractThe evolution of the cold deformation microstructure is described for medium to high stacking fault energy, single phase fcc metals. Macroscopic strain accommodation for polycrystalline metals is considered, and it is suggested that grains subdivide during deformation on a smaller and smaller scale, and that each volume element is characterised by an individual combination of slip systems. A number of microstructural observations (especially of aluminium, nickel, and copper) are described, and dislocation arrangements are discussed on the basis of the general principle that they are low energy dislocation structures. It is shown that the microstructural evolution is quite similar in polycrystalline metals and in single crystals deforming by multislip, and ways in which metallurgical parameters such as stacking fault energy and grain size can affect the microstructure are examined. The general principle of grain subdivision during cold deformation is discussed with reference to the microstructural observations.MST/1290

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1039

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe principles of texture evolution during the rolling deformation of fcc metals are presented, and effects which enable texture formation and local structure evolution to be correlated are analysed by comparing experimental rolling textures in fcc metals with the results of theoretical predictions based on homogeneous slip on discrete slip systems (Taylor type models). The assumptions of partially relaxed constraints conditions, and the influence of high deformation on deformation structure and its consequences for local texture effects and local grain arrangement, are discussed.MST/1291

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1048

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractTexture development during the thermomechanical processing of high strength aluminium alloys is reviewed. The alloys dealt with include both conventional heat treatable alloys, and unconventional materials such as rapidly quenched alloys and metal-matrix composites. The processing routes considered include hot and cold rolling, extrusion, forging, recrystallisation, and superplastic deformation. The information is presented as (111) pole figures and orientation distribution functions, in order to illustrate the much greater degree of detailed information that can be extracted from the latter method of analysis. The implications of texture development are considered by examining the effects that texture can have on tensile property anisotropy and fatigue and fracture behaviour.MST/1292

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1058

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe reasons for computer modelling the pass-by-pass development of microstructure during industrial hot rolling operations are briefly considered, and the principles of modelling are outlined. Quantitative relationships between the kinetics of static recrystallisation, recrystallised grain size and the variables of a rolling pass are compared for C–Mn steel and for Al–1 Mg/commercial Al, and the consequences for multipass rolling are discussed. For the steel, description of austenite grain structure in terms of grain size and residual strain leads to model predictions in good agreement with observation, and the value of modelling is well established. For aluminium, the same approach is shown to lead to anomalies, indicating that a more sophisticated description of microstructure is required. The possible roles of intermetallic particles are discussed.MST/1300

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1072

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe relationships between titanium alloy microstructures and mechanical properties are reviewed. The influence of hot working on microstructure development is discussed, and developments in high temperature processing, including superplastic forming and isothermalforging, and the use of hydrogen as a temporary alloying addition are considered. Recent work aimed at modelling the high temperature deformation and microstructure development is also examined.MST/1265

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1082

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory for recrystallisation has been modified by using an analytical approach and three dimensional computer simulations. A non-constant growth rate, the result of either spatial variations in the net driving force for the recrystallisation reaction, or simultaneous recovery during the reaction, has been considered. Either may account for considerable negative deviations from classical JMAK kinetics. The effect of recovery on transformation kinetics in the case of site saturated nucleation is analysed in detail. An inhomogeneous distribution of nucleation sites may also have a significant effect on the kinetics; leading to non-constant Avrami exponents usually much lower than the classical values of 3 and 4for three dimensional homogeneous site saturation and Johnson-Mehl nucleation kinetics, respectively. It is suggested that the near log-normal size distributions of grain section areas which are commonly observed experimentally may reflect a non-random distribution of nucleation sites. The modelling results are discussed in terms of experimental observations.MST/1294

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1093

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractFactors affecting textures in non-hardenable aluminium alloys are considered on the basis of published results and some new experimental results. Emphasis is placed on conditions relevant to industrial scale rolling and annealing of sheet products. The most commonly observed texture components in these alloys are summarised, together with available evidence regarding their origins. Hot rolling conditions have a powerful effect on subsequent annealing textures, which is attributed to the microstructural state of the material before cold rolling. This can influence the relative frequency of different nucleation mechanisms. Heat treatment of the hot rolled band can also bring about marked changes in texture and earing for the same reason. The effect of cold rolling reduction on texture is complex and depends on the initial microstructure; increasing reduction promotes an increasingly heterogeneous substructure. The main impurity in these alloys is iron, which plays several different roles in controlling texture and earing level. Iron, both in solid solution and as coarse precipitates, can weaken the cube texture and promote 45°earing tendency. However, fine scale precipitation in the deformation substructure before recrystallisation may contribute to a strengthening of the cube texture. For high contents of iron and heavy rolling reductions, where continuous recrystallisation occurs, the rolling texture is retained or may even become strengthened. Influences of silicon, manganese, and magnesium are also discussed.MST/1295

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1103

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractPrecipitation causes changes in the modes of plastic deformation and recrystallisation, as well as in the development of rolling and recrystallisation textures. The nature of these changes varies strongly with the size, shape, and density of the particles and, in particular, on whether the particles are cut by dislocations during deformation. This leads to numerous phenomena, some rather surprising, which are systematised, established through many new experimental results (mainly on aluminium alloys), and discussed.MST/1293

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1113

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThere have been important developments in steel products and steel manufacturing processes over the past thirty years, many of which have had major implications for cold rolled and annealed strip products. The development of microalloyed steels and their use in cold rolled and annealed gauges have resulted in a much better understanding of the role of second phase particles on deformation and recrystallisation characteristics. The development of dual phase steels, with their enhanced work hardening rates and improved resistance to plastic instability, has also had an impact on sheet metal products. Products have also benefited from improved steelmaking practices, as for example in the manufacture of clean steels and the use of vacuum oxygen decarburisation processes. The advent of continuous casting and the associated deoxidation practices have required substantial technological development with regard to the subsequent processing routes and product properties. A similar change is happening with the introduction of continuous annealing. These developments and some of the background metallurgical principles are discussed.MST/1296

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1131

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractThe processes and mechanisms controlling grain growth in crystalline solids are reviewed. The driving forces governing the overall process are considered, and a distinction is made between normal and anomalous grain growth. The influence of solutes and dispersions (soluble and insoluble, coherent and incoherent) is discussed. Recent experimental studies of grain growth in model and commercial materials are surveyed.MST/1297

ISSN:0267-0836    

DOI:10.1179/mst.1990.6.11.1136

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor