摘要:

AbstractThe range of applications of titanium and its alloys has broadened considerably in recent years as advances in the users' technologies have brought appropriate responses from the titanium industry. Alloy development to match improvements in aircraft gas-turbine engines is the prime example; useful alloys must strike a balance between creep strength, fatigue strength, and fracture toughness. Dramatic changes in manufacturing techniques are currently widening the range of uses for titanium in airframes, where the metal now accounts for about 7% of the structural weight for commercial aircraft and 20–25% for military aircraft. Other major areas of use are in general and marine engineering, heat exchangers and steam condensers, chemical and electrochemical plant, and surgical implants. Titanium is now an everyday engineering material with a price per unit volume in between stainless steels and nickel-base alloys.MST/106

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.257

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractA process is described whereby polymer films are laminated using vacuum-deposited aluminium as an adhesive. Only modest pressures are needed to produce a pressure weld between the freshly deposited metal coatings. The influence of various process parameters on the metal–metal bonding is explored, with particular reference to surface contamination and deposition rate. In addition to their commercial potential, the laminates are particularly useful as test specimens for measuring metal–polymer adhesion.MST/178

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.263

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractFrom an analysis of the local atomic arrangement in orderedγ′-particles it is deduced that the effect of dislocation splitting on the critical resolved shear stress ofγ′-hardened materials is very small. This result is in striking contrast to the ones obtained for lattice misfit and modulus hardening.MST/146

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.268

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe precipitation reactions responsible for age hardening in a high-conductivity Cu–Cr–Zr–Mg alloy have been investigated by analytical transmission electron microscopy and compared briefly with the processes that occur in simpler Cu–Cr and Cu–Cr–Mg alloys. Aging at low temperatures (400°C) results in the formation of Guinier–Preston zones. Peak hardness, obtained by aging for 24 h at 450°C, is found to be a result of the fine scale precipitation of an ordered compound, possibly of the Heusler type, with the suggested composition CrCu2(Zr, Mg). Overaging results in the formation of coarse precipitates of Cr and CU4Zr. The intergranular precipitate which forms in the Cu–Cr–Zr–Mg alloy is Cu4Zr. This phase precipitates both as discrete particles on the grain boundaries and as thin ( ~ 5 nm) continuous intergranular films.MST/89

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.270

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractFactors controlling the degree of vanadium strengthening developed in series of 0·6 and 0·8% C rods by a wide range of forced-air cooling treatments have been examined. Multiple linear-regression analysis has been applied to quantify the strengthening effect of vanadium in terms of precipitation strengthening and changes in the ferrite–pearlite microstructure. The possibility of an effect from the dislocation substructure has been considered qualitatively. The precipitation-strengthening contribution decreased with increasing cooling rate, and this effect was more pronounced at the lower carbon level. These effects have been related to the degree and size of V(CN) precipitation. However, the tensile strength of these materials increased as the cooling rate was accelerated, and it has been shown that the loss in dispersion strengthening is more than compensated for by concurrent increases in interstitial and microstructural strengthening. The successful application of this work to commercial rod production has been described.MST/145

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.276

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe dynamic aging of an 18 wt-%Ni 250 maraging steel was investigated. The first stage of dynamic aging is suggested to be the formation of Mo atmospheres on dislocations, which occurs at approximately 204°C. The activation energy for Mo-atmosphere formation was found to be 1·01–1·38 eV. It is also suggested that Mo clustering in the matrix independent of the atmosphere–dislocation interaction occurs in the first stage of dynamic aging. In the later stage of dynamic aging, the Mo atmospheres are depleted from the dislocation lines by a precipitation reaction which occurs during the arrest period of the dislocations at the matrix Mo clusters. The second stage of dynamic aging (depletion of Mo atmospheres and growth of matrix Mo clusters), occurs at and above 316°C. As the growth of the Mo clusters progresses, a driving force for Ni diffusion to the clusters occurs in order to form matrix Ni3Mo precipitates. Ni diffusion to the Mo clusters occurs with an activation energy of 2·7-3·2 eV, and is considered to be the rate-controlling process sustaining the later stage of dynamic aging. As the reaction in the matrix begins to saturate, the dislocations retain the remaining Mo as atmospheres. At this point, Ni begins to diffuse to the dislocation lines, where a precipitation reaction to form Ni3Mo directly on the dislocation lines occurs.MST/109

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.285

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe superplastic behaviour of a microduplex Fe–Cr–Ni (25·7Cr–6·6Ni) alloy was investigated in the as-worked, annealed, and prestrained conditions. In the early stages of deformation, flow stress depends significantly on strain, and also on the instantaneous microstructural state in the case of as-worked and annealed specimens. Under these conditions, the empirical parameters of the constitutive equation for superplastic deformation were found to depend systematically on strain. At 1000°C, strain hardening predominates, and this could be accounted for by grain growth and by the hardening produced by the noticeable dislocation activity. After suitable prestraining, steady-state deformation conditions may be attained; this may facilitate the collection ofσ–εdata, which could then be used to assess the relative importance of the appropriate deformation mechanisms.MST/125

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.291

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe effects of aging at 773 K on hydrogen embrittlement in Ni–30Cr (wt-%) alloys having two levels of P have been investigated by considering the grain-boundary segregation of impurity atoms and the Ni2Cr ordered-phase formation. Aging at 773K suppressed intergraular fracture and reduced the susceptibility to hydrogen embrittlement in the low-P alloy. Such behaviour can be explained in terms of the grain-boundary strengthening caused by the segregation of C atoms. During aging at 773 K, the Ni2Cr ordered phase formed and the deformation mode changed from wavy slips to coplanar slip with paired dislocations, and then to coplanar slip with microtwins. In the low-P alloy, this change of deformation mode induced step-like cracks which may have occurred by the separation of either the {111} slip planes or the microtwin interfaces. In the high-P alloy, aging for short times caused C segregation to the grain boundaries which suppressed intergranular fracture. However, aging for longer times induced drastic intergranular hydrogen embrittlement because of the grain-boundary segregation of P atoms, which offset the effect of the boundary strengthening caused by C atoms.MST/177

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.297

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractA study has been made of the effects of the addition of strontium, primarily at a level of 0·04 wt-%, on hydrogen absorption by molten Al–Si alloys of the LM 6 type, and on the solidification characteristics of the modified alloys as a function of cooling rate. Strontium enhanced the susceptibility of the alloys to hydrogen pick-up, the hydrogen concentration reaching a plateau during a 1 h hold period. With decreasing cooling rate, the strontium-modified alloys solidified with a scalloped eutectic interface growth front which is associated with a delay in forming a complete solid shell at the mould wall.MST/108

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.305

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe morphology, crystallography, and chemistry of phases present in an as-cast commercial aluminium bronze containing iron, of nominal composition (wt-%) Cu–10Al–2·5Fe (BS 1400: AB1), and the development of microstructure on cooling from elevated temperatures, have been studied using optical and electron microscopic techniques. The as-cast microstructure consists ofα-phase, martensite, and iron-rich intermetallic precipitates. Theα-phase is fcc copper-rich solid solution and exhibits a Widmanstätten morphology. The martensitic phase, which is derived from the high-temperatureβ-phase, has the 9R crystal structure. The intermetallic particles are based on Fe3Al and have the Do3structure. These iron-rich particles are precipitated in theβ-phase and cause a refinement of the microstructure by providing sites for the nucleation of theβ-phase, to some extent, by impeding the growth of theα-phase.MST/150

ISSN:0267-0836    

DOI:10.1179/mst.1985.1.4.312

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor