摘要:

AbstractThe influence on the aluminium matrix of chemical modification by addition of strontium or sodium has been investigated in 356 aluminium alloy cast in a permanent mould. Solution heat treatment time and artificial aging time were the two variables examined for the heat treatment study. In the as cast condition, modification does not have an influence on the overall hardness (i.e. that of the aluminium matrix and eutectic silicon) or on the microhardness of the aluminium matrix. Modification does however have an effect on the aluminium matrix of the heat treated alloy. The hardness and yield strength of the modified alloys are lower after the T6 temper compared with the unmodified alloy. Hardness–yield strength relationships have been established.MST/1953

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.757

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractFour rapidly solidified, potentially structural, Mg–Al alloys were produced by gas atomisation. Alloying additions of Zn or Si were introduced to evaluate their effects on structure and properties. The powders were consolidated by hot extrusion, producing fully dense materials. A structural investigation was carried out using optical and electron microscopy and phase identification was achieved using X-ray diffraction and energy dispersive X-ray analysis. The mechanical properties evaluated included tensile and compressive strength together with fracture toughness. The response to aging of the alloys was also determined. In general the properties were promising considering the relatively simple chemical compositions involved.MST/1966

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.763

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe development of recovery and recrystallisation in cold rolled Al–4·5Mg–0·7 Mn (designated AA 5083) was analysed metallographically, by measuring hardness and electrical conductivity, and by means of texture analysis. The precipitation state and the initial texture were varied using appropriate pretreatments before cold rolling in order to study the influence of these parameters on kinetics and texture evolution during deformation, recovery, and recrystallisation. Finally, the results obtained were compared with those obtained for conventionally produced material.MST/1960

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.771

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA new casting process for fabricating short fibre reinforced metal matrix composites via the centrifugal force infiltration of fibre preforms with molten aluminium alloys is described. The effect of processing variables, such as pouring temperature, preheated mould temperature, and time of application of centrifugal force, on the infiltration kinetics and resultant microstructure is discussed. Composites having fibre volume fractions of 4·5, 8·0, 12, and 16% were obtained via this method. Comparisons with existing infiltration technology and the mechanical properties of the composite are presented.MST/2000

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.783

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA recently reported simple method for estimating the cohesion of titanium carbide, based on bond energies, is extended to the corresponding carbides of the other group IVA and VA metals. The extra d electron in an atom of the latter produces some significant although small differences, notably a more definite decrease in cohesive energy, as x is reduced in MCx, which is consistent with the more limited composition range of the MC phases of group VA metals. Various second order corrections to the estimated cohesive energies of TiCxcompounds, including C–C interactions and entropic effects, enable estimates to be made of the phase limits and the primary solubility of C in Ti. An explanation is also offered for why TiC has a fcc, rather than a hcp, metal sublattice.MST /2049

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.788

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA two dimensional probabilistic cellular automaton model has been developed to simulate the evolution of a dendritic grain structure during the solidification of an undercooled pure melt. The computer model incorporates rules for simulating heat transfer and grain nucleation and growth, as well as routines that enable short and long range transport of grains in the melt. Grain growth is restricted by procedures simulating latent heat rejection and capillarity. The model is used to examine the influences of the degree of undercooling and of chilling of the melt surface on grain structure.MST/2008

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.793

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA Ti–6Al–4V/σ(SM 1240) composite prepared by diffusion bonding has been studied in the as received condition, using Auger electron spectroscopy, transmission electron energy loss spectroscopy, and scanning electron microscopy. The SiC basedσfibre has a tungsten core, and a duplex coating of carbon (adjacent to the SiC deposit) and TiBx. It is shown that boron from the TiBxlayer diffused into the matrix and formed TiB needles. Carbon was detected in the TiBxlayer and was present in elemental free form. A continuous SiO2+ carbon layer was detected at the SiC/carbon layer interface. Analysis of in situ fracture composite surfaces in an Auger spectrometer has shown that the tensile failure was initiated within the carbon layer or at the TiBx/matrix interface. An oxide layer detected at the TiBx/matrix interface influenced the fracture behaviour of the composite.MST/2027

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.797

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA continuous SiC fibre reinforced Ti–6Al–4V composite was diffusion bonded in transient liquid phase to Ti–6Al–4V alloy plate using Ti–Cu–Zr amorphous filler metal. Joint strength increased with bonding time up to 1·8 ks and reached the maximum value of 850 MN m−2which corresponded to 90% of the tensile strength of Ti–6Al–4V. The extent of deformation of Ti–6Al–4V in the vicinity of the bonding interface was small compared with that of solid diffusion bonding because of the low bonding pressure. The bonding layer had an acicular microstructure which was composed of Ti2Cu andαtitanium with dissolved zirconium. Brittle products such as (Ti, Zr )5Si3or (Ti, Zr )5Si4were formed at the interface between the SiC fibres and the filler metal. These products existed only at the end of fibres, in very small amounts, therefore joint strength was not significantly affected by the products.MST/1989

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.807

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe fracture ofαiron and C–Mn submerged arc weld metal at temperatures below the brittle–ductile transition temperature is examined. The probability of intergranular fracture occurring in a regime where cleavage fracture is observed is considered with respect to simple theoretical arguments that take into account the geometry of grains and the relative energy of the two fracture processes. The experimental observations are examined in relation to the predictions of these arguments. Simple geometrical arguments demonstrate that a small proportion of intergranular fracture is expected to accompany cleavage fracture in most specimens of polycrystallineαiron and ferritic steels fractured at temperatures below the brittle–ductile transition temperature.MST/1943

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.813

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractMetallographic and X-ray examination have been employed to investigate the effects of cathodic charging five commercial 300 series stainless steels having different austenite stabilities. Although the introduction of hydrogen at high fugacities produces bothɛandαmartensite in all of the steels, the tendency to formɛis greatest in the austenite of highest stability. This is not consistent with the expected effect of stacking fault energy, but the incidence ofɛformation is greatest in the steels with the lower Mdtemperatures, apparently because transformation toαmartensite becomes more difficult in these circumstances. Reversion to austenite occurs to some extent on aging at room temperature and is rapidly completed when hydrogen is driven off at higher temperatures.MST/1942

ISSN:0267-0836    

DOI:10.1179/mst.1994.10.9.817

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor