摘要:

AbstractThe equilibrium phase diagrams of Al–Cr, Al–Zr, and Al–Cr-Zr, with particular reference to aluminium-rich alloys, have been critically reviewed. On the basis of these, and consistent with measured thermodynamic values, the binary systems have been thermodynamically characterized. Using these characterizations, phase equilibria have been extrapolated in the ternary, with the intention of augmenting the sparse experimental information concerning the equilibrium liquidus (0–10 at.%Cr, Zr) and solid solution range of aluminium in Al–Cr–Zr. Using the same parameters that define the equilibrium phase relationships, metastable phase relationships can also be extrapolated into the ternary.MST/418

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.520

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractTie line coordinates of ternary Cu–Ag–Au alloys in the solid immiscible region of the equilibrium phase diagram were determined experimentally by electron probe microanalysis. The two solid phases were analysed in samples which had been thermally treated from the as–cast condition to coarsen the phases. Tie line coordinates were also calculated theoretically using a thermodynamic model which is an extension of the regular solution model. The theoretical calculations agree well with the experimental analysis of the copper–rich phase as well as with a corrected analysis of the silver–rich phase. The necessity for the correction was attributed to the thermal coarsening treatment of the samples.MST/191

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.528

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA method for viewing the detailed solid/liquid interface morphology of metallic eutectic systems has been developed. It is based on an apparatus designed to allow the unidirectional solidification of metallic samples having low thermal mass at considerably lower, and more stable, growth rates than have previously been possible with conventional equipment. As a result, high resolution quench interfaces can be produced which in quality rival those of transparent organic analogue systems. Application of this technique to the solid/liquid interface of the Pb–Sn–Cd ternary eutectic has revealed a number of new facts. It was discovered that the Cd phase forms a facet plane coplanar with its basal plane and with the Pb/Cd lamellar habit plane. Qualitative observations of the differing behaviour of the Pb and Sn phases in contact with the Cd facet plane allowed the magnitudes of the three solid/solid interfacial free energies to be compared and a mechanism for the formation and stabilization of the ABCBA lamellar structure to be postulated.MST/352

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.534

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractIn order to gain knowledge of the nickel–rich corner of the Ni–Cr–Hf phase diagram, microstructures of cast alloys and their evolution towards equilibrium conditions have been followed by optical and scanning electron microscopy, microprobe analysis, and quantitative metallography. The evolution of as–cast microstructures involves the development of a Ni5Hf plate–like precipitate in two–phase alloys, and various morphological changes in three–phase alloys. As–cast structures are compared with those obtained by arc melting. Direct processing of the scanning electron microscope image has proved to be a valuable tool for microstructural characterization of the transforming phases.MST/349

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.539

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe effects of isothermal annealing between 800 and 1200°C on the microstructure of single–crystal SRR 99 have been investigated. During aging at either 800 or 900°C, the precipitates adopt an irregular, rounded, and highly interconnected array which suggests that they have undergone coalescence. Aging at higher temperatures was found to produce a regular cuboidal precipitate morphology, although long–term aging promoted the formation ofγ′-‘rafts’. The precipitate size distributions were found to be broader than those predicted by the Lifshitz-Slyosov and Wagner theory, and the coarsening kinetics also showed significant deviations from the power law prediction of this theory. The reasons for these deviations are discussed in the light of the available models, and it is suggested that a progressive transition in the dominant coarsening mechanism takes place.MST/371

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.543

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe aging behaviour of Al–3Cu and Al–3Cu–0·1Be alloys has been investigated using microhardness and transmission electron microscopy techniques. The Al–3Cu–0·1 Be alloy was found to have a significantly higher hardening rate than the Al–3Cu alloy at room temperature and 110°C. An Al–0·2Be alloy showed no age hardening tendency at room temperature. The hardening in Al–3Cu alloy is the result of Guinier–Preston (GP) zone formation; no GP zones were observed in Al–3Cu–0·1Be alloy aged at room temperature and 110°C, and an additional aging at 150°C was required to initiate GP zone formation. The higher hardening rate for the Al–3Cu–0·1 Be alloy is attributed to the early and extensive formation of vacancy loops adjacent to network dislocations, the loops acting as barriers to the glide of network dislocations. The formation of Cu–Be–vacancy clusters may be the cause of the accelerated hardening rate, and this is discussed.MST/309

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.547

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA detailed microstructural study of heavily rolledα-brass has revealed that in addition to straight shear bands a‘wavy’structure is also present. The cold-rolled material is considered to exhibit laminar structures and properties that are similar in some respects to the behaviour of laminar composite materials. This is examined in detail and conditions for shear band formation and propagation are investigated in terms of flow localization in laminar structures.MST/250

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.552

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe formation and growth of voids on the grain boundaries of a Nimonic 105 superalloy subjected to high temperature and stress has been followed using small-angle neutron scattering. The size of the voids increases with treatment time and is well correlated with the creep. The volume and surface fractions of the voids are evaluated.MST/140

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.559

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA commercial type dual-phase steel has been heat treated to develop a conventional dual-phase structure and, by a double-quench heat treatment, a dual-phase structure with a small martensite island size. These specially heat treated materials together with the normalized material have been plastically deformed by rolling to a reduction of 98% (εt= 4·0). The tensile properties have been determined after deformation and correlated with the microstructure. It has been found that within the strain rangeεt= 0·5–1·5 the work hardening modulus is similar to that of pure iron. Over a narrow strain range little work hardening occurs but within the rangeεt= 2·5–4·0 the work hardening modulus is greater than that of ferrite. The increase in modulus seems to be associated with the plastic deformation of the martensite islands which, at the highest strains, give a fibre reinforcing effect. The results are discussed in relation to the work hardening mechanisms involved. It is concluded that changes in the ferrite grain size, established during the development of deformation bands at lower strains and subsequently deformed at higher strains, greatly influence the flow stress through a Hall-Petch relationship.MST/241

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.564

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAn assessment has been made of the overheating behaviour of three low-alloy steels used in the electric power generating industries. The steels, 1Cr–Mo–V, 2·25Cr–1Mo, and 3·5Ni–Cr–Mo–V have been prepared as high-purity versions with low tramp element contents, sulphur contents of 0·001%, and manganese contents of 0·02 and 0·2%. For comparison, commercial steels produced by good practice and containing 0·006–0·011%S and 0·17–0·21%Mn have also been examined (all compositions in wt-%). The upper shelf energies of the high-purity versions of the steels in the fully heat treated condition indicate that these steels do not overheat after treatment at temperatures up to 1400°C, whereas the commercial versions do overheat and, in some cases, show a severe reduction in their impact energy levels. In some cases, the high-purity steels show an unusually low tendency to austenite grain growth after reheating at temperatures up to 1400°C. The results obtained show that new specifications for low–alloy steels could be developed which would give freedom from overheating during forging and greatly improved upper shelf energies after heat treatment.MST/362

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.6.571

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor