摘要:

AbstractAdhesives have several advantages over mechanical fastening, and the use of bonding is steadily increasing in many applications. Bonding of primary structures in aircraft has been used for many years and much more research has been directed towards aluminium than any other material. Joint performance depends on the alloy, pretreatment, primer, and adhesive. Many studies of these variables have been made, often making use of modern surface analytical techniques. Informative studies have also been carried out on titanium and steel. Hot, humid conditions, especially combined with stress, can be especially damaging to metal joints. A full understanding of the factors that provide the best resistance to this damaging effect has not yet been achieved. However, stable oxide layers with the correct topography appear critical and selection of the correct pretreatment is therefore of paramount importance.MST/475

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.761

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA series of lead–natural rubber composites have been produced on a laboratory scale, and their X-ray protection power measured. The effect of antioxidants on the physicomechanical properties and aging characteristics of the composites was investigated. Flex properties and age retention properties showed perceptible improvement upon the addition of antioxidants without changing the X-ray shielding power. An attempt was made to study the morphology of the fractured surfaces of the composites.MST/347

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.768

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractActivities of iron in both theα- andγ-phases of Fe–Co alloys determined by the solid electrolyte emf technique in the temperature range 1023–1473 K are reported. Activities are found to exhibit negative deviation from Raoult's law in both phases. The extent of this deviation decreases with increasing temperature. The results are compared with those of other workers.MST/39

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.773

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractDiffusion reactions have been investigated under high pressures of up to 3·3 GPa in the Al–Mg system. Theβ-,γ-, andε- phases appeared in the diffusion zone under vacuum, but only theγ- phase was found in the diffusion zone under high pressure. The occurrence of this phase in the diffusion zone is discussed using computed phase diagrams of the Al–Mg system under high pressure.MST/402

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.777

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe high strength of some Al–Cu–Mg–Ag alloys has been attributed to very thin (~2·5 nm), but broad, hexagonal-shaped precipitates. Previous work has shown that the precipitates have a hexagonal unit cell, but different lattice parameters have been reported. In the present paper, the intensities of X-ray diffraction reflections from the precipitates have been measured on Buerger precession photographs, and it is shown that the crystal structure is monoclinic (space group P2/m) with the parameters a = b = 0·496 nm, c = 0·848 nm,γ= 120°. The special values of these parameters confer a hexagonal symmetry on the lattice. This unusual structure is a slightly distorted form ofθ-CuAl2, to which it appears to change after long aging times at 200°C.

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.784

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractTwo binary Al-rich Al–Nb alloys containing 4·5 and 7·7 wt-%Nb have been rapidly quenched from the liquid state using the‘gun’technique. Transmission electron microscopy and diffraction techniques have been extensively employed to characterize the as quenched as well as externally heat treated alloy foils. Each alloy in the as-quenched state shows only a supersaturated solid solution, indicating a substantial increase in the solid solubility limit of Nb in Al by rapid quenching. Elongated solid solution grains and defect structures have also been observed in the as-quenched foils. While no precipitation was found to occur on annealing the quenched dilute alloy (Al–4·5Nb) foils for 1 h at 673 K, precipitation along grain boundaries was observed in the concentrated alloy (Al–7·7Nb). Higher temperature annealing (≥773 K) resulted in the formation of a new metastable phase having an ordered fcc GeCa7type structure with a lattice parameter a ~ 0·8 nm. This phase forms predominantly with a rodlike morphology and is arranged in a Widmanstätten pattern inside the grains, although fine precipitate particles have also been observed. On prolonged annealing at or above 773 K, the metastable phase transforms with the formation of the equilibrium tetragonal Al3Nb phase.MST/391

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.788

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe microstructural changes, precipitation behaviour, and mechanical properties of typical austenitic stainless steels (304 H, 316 H, 321 H, 347 H, and Tempaloy A–1) have been examined after long-term aging. The steels were aged statically in the temperature range 600–800°C for up to 50000 h. The microstructural changes were observed by optical and transmission electron microscopy, and the extracted residue was identified using X-ray analysis. Time–temperature precipitation diagrams were made for each steel. The amount ofσ-phase was measured in samples aged at 700°C. The hardness and impact-value changes, and the tensile properties of aged samples were measured.MST/358

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.795

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe effect of carbon in different states of dispersion has been examined in relation to its effect on the texture formed during the annealing of cold-rolled steel sheet. Quantitative texture analyses using orientation distribution functions have been combined with detailed metallographic investigation of changes taking place during recrystallization. Calculations have also been carried out on the rate of dissolution of carbon from cementite particles for a range of relevant conditions. Dissolved carbon present before cold rolling greatly reduces the final annealed {111} texture strength and leads instead to a spread around the Goss orientation. Dissolved carbon present with manganese during annealing also reduces the final {111} intensity, tending to replace it with a number of relatively weak minor components; this is observed during conditions of slow heating, or when primary carbide particles are numerous, and seems to be associated with a significant nucleation rate of new grains during the later stages of recrystallization.MST/389

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.807

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe influence of prior austenite grain size dγ, and true interlamellar spacing of pearlite Ston the strength and fracture toughness of a eutectoid rail steel has been investigated. Specimens were machined from rail sections and heat treated to produce a wide variation in dγand st. Mechanical properties studied included 0·2% proof stressσ0·2, ultimate tensile strengthσu, tensile ductilityδ, cleavage fracture stressσf, and plane strain fracture toughness K1c. All tests were performed at a temperature of−80°C. The values ofσ0·2andσuincrease as stdecreases. The proof stress is related to the mean free distanceλin the pearlitic ferrite by a Hall–Petch equation. A microstructural dependence similar to that ofσ0·2is shown byσfand for all but the finest pearlitesσfis interpreted as a shear stress controlled cleavage nucleation stress. The value of K1cfirst decreases with decreasing stand then increases for the finest spacings. This behaviour is attributed to a change in the micromechanism of cleavage nucleation as the pearlite spacing changes from coarse to fine. The value of dyhas very little effect on K1c, butδdecreases progressively as dγincreases. The effect of dγon K1cis negligible because the fracture process zone is much smaller than the grain size and therefore the grain boundaries cannot influence the fracture processes occurring at the crack tip. The tensile ductility is interpreted as the strain necessary to develop an internal microcrack which then propagates as a quasibrittle fracture. The size of the microcrack is shown to be related to the pearlite nodule size which in turn is related to dγ.MST/396

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.816

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractSlip distribution has been varied in a series of Al–Mg–Si alloys of similar yield strength and grain size, by altering the amounts of manganese-bearing dispersoid and by under- and overaging, which also altered the precipitate-free zones and grain boundary strength. It has been found that fatigue crack propagation thresholds increase with an increase in dispersoid content, as slip is homogenized. However, for a given dispersoid content, under- and overaged alloys have similar crack propagation behaviour. This effect is interpreted in terms of slip distribution and grain boundary strength in the various microstructures.MST/398

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.8.823

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor