摘要:

AbstractPart 1of this review was a critical overview of the general subject of adhesion in dentistry and dealt with various interfacial phenomena affecting modern dental practice. The second part examines the particular problem of adhesion to teeth. The areas covered are: the nature of tooth substance; modern dental restoratives; current solutions to the adhesion problem; problems with laboratory test methods; fundamental studies such as contact angle measurements; and bioadhesives. Areas requiring further research are indicated where possible.MST/1454

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.785

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractTwo models have been proposed which can be used to predict the occurrence of liquid immiscibility in ternary metallic alloys. One model, derived from an earlier proposal by Axon for predicting liquid immiscibility in binary alloys, was based on differences in the atomic sizes and melting points of the metals. The second model, based on a proposal made by Mott (from the binary metallic liquid immiscibility rule of Hildebrand and Scott), utilises solubility parameters and electronegativities as the determinants. The models were tested against the known behaviour of 27 metallic ternary systems which show liquid immiscibility and 36 systems which show either complete liquid miscibility or only a small region of liquid immiscibility confined to a region adjacent to an immiscible binary system. Both models showed good predictive ability when applied to the first group of 27 systems, but the first model proved to be superior when applied to the 36 miscible liquid systems. The behaviour of the liquid phase was always predicted correctly by one or other of the models in all the ternary systems examined.MST/1412

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.795

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe development of an accurate, yet simple, transformation and hardenability model for general use in the heat treatment and steelmaking industries is described. An empirical approach is used, based on both continuous cooling transformation (CCT ) diagrams and hardenability literature. For this purpose, an equation is developed relating hardenability and the critical time requiredfor transformation during continuous cooling. Existing hardenability models and CCT diagrams are analysed to determine a correct mathematical structure for the hardenability multiplication factor equation. The multiplication factor for a fixed weight percentage of an alloying element X isfound to be strongly dependent on carbon content (in wt–%) according to the equationℳ=(K%Cn)X, where K and n are constantsfor a specific alloying element. Best values of K and nfor the various alloying elements are determined. Very strong interactions (high values of |n) between the carbide forming elements and carbon are reported. The multiplication factors for the carbide forming elements increase exponentially with carbon content. The accuracy of the model proposed is compared with that of existing models, in which a constant carbon effect onℳhad been assumed, for a wide range of both low and medium carbon steels, and it is shown that significant improvements in accuracy are obtained using the new model. This is attributed to the use of the improved harden ability multiplication factor equation, which reflects the variable influence of carbon content.MST/992

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.803

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe silicide chemistry, i.e. the type, composition, and lattice parameters of the silicide in as cast titanium based Ti–Si–Al–Zr alloys, has been studied. It has been shown that the stoichiometry of the silicide in the alloys can be expressed as (Ti1−x, Zrx)5(Sil−y, Aly)2·76−3·04(0≤X<0·2, 0≤y<0·1). The presence of Al and Zr in the silicide increases its lattice parameters. Addition of Al coarsens the eutectic silicide and slows the formation of secondary silicide precipitates by solid state reaction. Addition of zirconium refines the eutectic silicide and promotes secondary silicide precipitation. The silirides are low in Al and rich in Zr, whereas the Ti matrix is rich in Al and low in Zr. The lattice parameters of the Ti matrix are decreased by Al and increased by Zr.MST/1427

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.812

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractMultistage torsion tests in the temperature range 1200–900°C and strain rate range 0·1–2·0 s−1were carried out to study the static recrystallisation (SRX) kinetics of 301,304,316, and 317 steels under iso- and anisothermal conditions. The fractional softening decreased with decreasing temperature, pass strainεi, and strain rate. The fraction recrystallised was plotted according to the Avrami expression. The temperature compensated timefor 50% SRX was a function ofεto the power of−2 and of the Zener-Hollomon parameter Z to the power of−⅜. The activation energy for SRX QSRXwas determined and compared with extensive results from the literature. The effect of accumulated strain is reflected in the decrease of QSRXfor all alloys. The SRX grain size is fitted by the Barraclough expression, in which it is a function of original grain size, ;amp;epsilon;, and Z. Finer grain sizes were obtained from accumulated straining in multistage anisothermal tests than from continuous straining, in which only dynamic recovery and dynamic recrystallisation were operative.MST/1249

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.818

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe microstructures of Ti–Al layers produced by laser surface alloying of a Ti substrate have been investigated for Al contents in the range 17–36 at.–%. The alloyed layers were obtained using a continuous wave CO2laser and a powder feed technique employing the following laser processing parameters: 1·8 kW power, 3 mm beam diameter, 7 mm s−1traverse speed, and feedrates of Al powder ranging from 0·03 to 0·07 g s−1. The microstructures were disordered lath martensiteα′in 17 at.–%Al alloy, ordered massive and acicular martensite in 23 at.–%Al alloy, and ordered massive, acicular, and lath martensite in 30 and 36 at.–%Al alloys. The change in martensite type and morphology is discussed in relation to the available datafor theβtoα′transformation in Ti alloys.MST/1437

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.827

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractLow strain cold deformation and annealing techniques have been applied to establish the effects of composition and heat treatment variables on the recrystallisation behaviour of Al–Fe alloys. The parameters controlling the critical strain required to initiate recrystallisation and the grain size produced by subsequent recrystallisation annealing have been established to be the volume fraction of secondary phases, the eutectic colony size in both as cast and processed material, matrix composition, the initial grain size preceding final cold deformation, the amount of deformation before annealing, and the final annealing temperature. The results derived from the application of the strain annealing test showed that increasing the volume fraction of secondary precipitate phases, the homogenisation and final annealing temperatures, or the eutectic colony size, decreases the critical strain and increases the maximum grain size produced after annealing, but increasing the initial grain size has opposite effects on these parameters.MST/1348

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.835

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractAn assessment has been made of the viability of producing Fe–Ti(O,C) metal matrix composites by the one step carbo thermic reduction of iron-ilmenite and iron-rutile mixtures with coal. Pelletised mixtures of iron, rutile or ilmenite, and collie coal were heated in a tube furnace to temperatures between 1300 and 1600°C under flowing argon. The microstructures of reacted pellets were examined using optical and scanning electron microscopy and the phases present were characterised by X-ray diffraction. Excellent dispersions of the Ti(O,C) phase in the iron matrix were obtained at temperatures above 1450°C. The addition of fluxes of group II halides or BaSo4to the reduction mixture promoted separation of the Ti(O,C) productfrom the iron. Preliminary experiments on the scale-up of the reduction procedures are reported.MST/1361

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.842

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractAn investigation of 2·25Cr–1Mo–0·1C weld metal has been carried out using atom probe field ion microscopy. The weld metal had a microstructure consisting of bainitic ferrite and retained austenite, but no cementite. The carbon concentration at the austenite/ferrite interface was found to change abruptly, whereas the concentration of substitutional alloying elements was the same in both phases. No enrichment could be found at the interface.MST/1444

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.849

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractSubmerged arc welds of a 22Cr–3Mo–8Ni (wt-%) duplex stainless steel were aged in the temperature range 400–600°C to simulate stress relieving conditions of mild steel. Particular attention was paid to the relationship between toughness and microstructure. It was concluded that sufficient toughness could be obtained on aging in the range 500–550°C provided that the aging time did not exceed 10 h. At temperatures>550°C, rather rapid embrittlement occurred as a result of the precipitation of essentially R phase and to some extentπphase. At ~≤500°C, spinodal decomposition of ferrite caused embrittlement, albeit more slowly than the precipitate induced embrittlement. Precipitation of the Mo rich phases Randπwas found to cause depletion of Mo in solid solution in ferrite. This offers a possible explanation for the decrease in pitting corrosion resistance observed in previous work.MST/1426

ISSN:0267-0836    

DOI:10.1179/mst.1991.7.9.853

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor