摘要:

AbstractBiomaterials are materials that are used in medical devices that are intended to interact with biological systems. These medical devices include the now common hip replacements and prosthetic heart valves, and the less common neurological prostheses and implantable drug delivery systems. Biomaterials include the traditional stainless steel, titanium, polyethylene, and polymethyl methacrylate and the more biologically sophisticated calcium hydroxyapatite, surface modified polymers, and glass ceramics. In this paper, some of the principles that are involved in the selection and use of these materials in present and future medical devices are discussed.MST/663

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.797

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe testing of erosion resistant materials is usually performed on laboratory scale test rigs under accelerated wear conditions. The validity of this is questionable because of the dependence of wear mechanisms on a variety of impact parameters. Data are presented that have been obtained from such tests on a glass–ceramic (Silceram) which has been developed as a low-cost erosion resistant lining material. Various impact conditions have been investigated, including impact angle, particle velocity, and impact frequency. The data concerning the effects of particle velocity show very good agreement with one particular erosion model, although there is an apparent dependence on other test variables.MST/611

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.807

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA detailed examination has been undertaken of the influence of surface treatment on the adhesion of polyethylene fibres to epoxy resin. The pull-out adhesion has been determined for untreated, chromic acid treated, and plasma etched monofilaments with different draw ratios and thermal annealing treatments. In a few cases, additional chemical treatments were applied to plasma treated fibres before the pull-out test. The polyethylene surface energy also has been determined by measurement of contact angle. The results, taken together, suggest that the adhesion depends on three factors: (i) the wettability (or physicochemical interactions), which is affected by the extent and nature of the surface treatment as well as the fibre draw ratio; (ii) the surface roughness, after plasma etching only, where a honeycomb structure of pits permits mechanical keying between the fibre and the resin (this structure has been examined by scanning electron microscopy); and (iii) the number of chemical bonds per unit area between the fibre and the resin. It is concluded that these three factors can be regarded as additive and that optimum results are obtained when their respective pull-out strengths reach their maximum values, ~2, ~3, and ~1·7 MN m−2.MST/640

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.814

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractAdding small amounts (<1wt-%) of both magnesium and silver to an aluminium alloy containing about 4 wt-% Cu causes precipitates with a hexagonal structure (Ω-phase) to form on {111} planes of the aluminium lattice. Precipitation ofθ′on {100} planes may also occur, the relative proportions of the two types of precipitate being dependent on the levels of magnesium and silver, e.g. ~0·7 wt-% of each element almost entirely suppressesθ′formation. Even whenθ′does form in parallel withΩ-phase, on prolonged aging it tends to dissolve in favour ofΩgrowth. Using an X-ray technique to establish foil thickness, the relative amounts ofΩandθ′precipitate have been measured as a function of aging time, analysis of the data showing that growth is diffusion controlled with an activation energy of 136±15 kJ mol−1.MST/648

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.827

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractSamples of concast Nb–V, Nb–V–Ti, and Nb–Ti steels have been examined using analytical electron microscopy. It has been shown that the addition of titanium to niobium-containing high-strength low-alloyed (HSLA) steels results in undesirable precipitation in the steels, i.e. precipitation of large precipitates with various morphologies. The composition and distribution of the large precipitates has been determined. The thermal stability of these large precipitates has been assessed by carrying out various heat treatments such as annealing at and quenching from temperatures between 1050 and 1250°C, and using heat cycles which simulate the heat affected zone in welds. It has been found that some of these large precipitates are stable up to 1150°C and some up to the melting point of the steels. The significance of these observations is discussed in terms of the addition of titanium to HSLA steels.MST/641

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.836

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA model which is experimentally supported has been derived which shows that the grain boundary carbide thickness (t) is inversely proportional to the carbide density t∝1/N, where N is the number of grain boundary carbides intersected per millimetre in a linear traverse. The number of grain boundary carbides generated on transformation from the austenite has been shown to increase with cooling rate and these higher N values were associated with thinner carbides according to the above relationship. No direct relationship as is usually assumed between the values of t and d (the grain diameter), i.e. t/d is constant, was found.MST/694

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.845

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe precipitation reactions occurring in C–Mn–Al and C–Mn–Nb steels before and after hot deformation have been examined and their influence upon hot ductility is discussed. Precipitation has been studied at 850°C, when ductility is poor, and also at 1100°C, when the ductility is good. Rapid intergranular precipitation occurred at 1100°C, but the precipitation present before deformation did not prove to be detrimental to ductility and grain boundary mobility at this temperature. Although only a limited amount of precipitation occurred at 850°C before deformation, intergranular precipitation continued during deformation resulting in embrittlement of the steels. At this temperature, strain induced transgranular precipitation of Nb(CN) occurred in the C–Mn–Nb steel and this is thought to be a major cause of poor hot ductility in this steel. By holding the steels for 15 min at 800–850°C before reheating to 1100°C, the area fraction of intergranular precipitation at 1100°C was increased. This produced a decrease in ductility at this temperature in the C–Mn–Al steel but had a less marked effect in the C–Mn–Nb steel.MST/107

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.849

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractAn attempt has been made to investigate the effects of aluminium, titanium, nitrogen, and boron on the hardenability of boron-bearing medium-carbon steels. It was found that not only titanium but also boron had the scavenging effect for dissolved nitrogen. A parameter designated as boron potential (Bp= xB−11/14(xN−14/47·9XTi), where xB, xN, and xTiare the total boron, nitrogen, and titanium content, respectively) was chosen to evaluate and predict the boron hardenability effect. From the results of this study, boron potential is a parameter useful in discerning the optimization of contents of titanium, nitrogen, and boron for the development of boron steels having excellent hardenability.MST/655

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.855

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractSurface preparation techniques of aluminium for adhesive joining in aerospace applications and their influence on bond formation have been reviewed. The mechanisms of the different pretreatments have been discussed with attention to the effect of alloying elements and conditions of the technique. On the basis of the morphology and physical and chemical state of the metal surface it has been attempted to characterize the adhesive-metal bond, its strength, and stability under adverse conditions.MST/546

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.860

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractSome results of recent work are reported. A diagram of the Au-rich part of the Au–Sn phase diagram is presented showing two peritectic reactions for values of Sn<25 at.-%. The diagram also supports the existence of an intermediate phase, which is stable up to 532°C, and which occurs between 8·5 and 10 at.-%Sn.MST/715

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.10.875

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor