摘要:

AbstractA Tian-Calvet microcalorimeter capable of operating to 1000°C has been used to determine the heats of mixing of the cubic phase in ZrO2–CaO, Zr O2–MgO, and Zr O2–CaO–MgO, and ZrO2–CaO–MgO systems as well as the heat offormation of Ca6Zr19O44compound. A power supply voltage monitoring technique and a method of determining the calibration constant developed in the work enable good experimental precision to be obtained using a single cell. The drop calorimeter was also used to measure the enthalpy difference of the samples between 298 and 1100 K.MST/3379

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.117

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractHigh resolution measurements of the displacements caused by the formation of bainite in a steel have confirmed that the surface relief due to each platelet in any given sheaf is identical to that of the others in a sheaf, and that the relief of each subunit conforms with the general features of an invariant plane strain. The maximum observed shear strain wasfound to be about 0·26, which is consistent with the magnitude expected from the phenomenological theory of martensite crystallography. Clear evidence has also been obtained of the plastic deformation induced in the adjacent austenite by the growth of bainite.MST/3270

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.121

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractA review is presented of the stabilisation of type 430 ferritic stainless steels, and the benefits and shortcomings of stabilizing elemental additions on the corrosion and mechanical properties discussed. Recent trends have been towards the use of dual stabilisation, or a combination of stabilising elements, and these combinations are also taken into account when comparing the beneficial and detrimental effects of each stabilising element. The cost and availability of each element are also considered.MST/3108

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.126

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractA review of the literature and current work indicates that the improvement in ductility at the low temperature end of the hot ductility trough in coarse grained steels tested at low strain rates, always corresponds to the presence of a significant volume fraction of ferrite;ferrite having excellent ductility. For good ductility 30–40%ferrite is required and this can be. achieved by deforming 20–30 K below the Ar3undeformed temperature. The higher the Ar3, the easier it is to deform and the narrower is the trough. Higher Ar3temperatures can be obtained by lowering the C and Mn levels, refining the grain size, or slowing down the cooling rate to the test temperature. These methods are discussed and the advantages of straightening during continuous casting, at lower temperatures rather than the currently preferred route using higher temperatures are outlined. Whereas straightening at higher temperatures only gives rise to small improvements in ductility (and these have not always been found adequate to eliminate transverse and edge cracking), straightening at lower temperatures when a significant amount of ferrite is present can give excellent ductility, more than enough to prevent cracking. The presence of ferrite will also ensure that the load requirements for bending are not excessive.MST/3257

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.132

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractUsing highly sensitive equipmentfor the measurement of small shear strains up to 1·5×10−4and their variation with time, the form of the primary creep curves for aluminium at low stresses has been determined. The extent and rate of recovery of these strains has also been measured to establish the pattern of anelastic behaviour, and best fit equations are presented. A unique activation enthalpy could not be identified for anelastic recovery, but a value for the activation enthalpy comparable with grain boundary or dislocation pipe diffusion was derived from primary creep when the strain exceeded 10−5. The ratio of the anelastic recovery strain to the forward creep strain decreased logarithmically with time over most of its range, but reached a limiting value that was dependent on the forward creep strain.MST/3265

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.139

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThe annealing behaviour of an Al–6 wt-%Ni alloy containing a dispersion of second phase particles has been studied. It is shown that for a particle diameter of 0·3μm, annealing takes place by extended recovery. However, for a particle diameter of 1·7μm, discontinuous recrystallisation occurs. The relationship between continuous and discontinuous annealing phenomena is discussed, and measurements of the particle limited subgrain and grain diameters are compared with theory.MST/3211

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.143

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractLittle is known about the exact form of the creep failure time distributions, and the presence of urifailed tests in most data sets adds to the complexity involved in such identification. Monte Carlo techniques were used to assess the relative efficiency of various methods available for estimating the parameters of the generalised gamma failure time distribution. The censored likelihood procedure was shown to be the least biased and most efficient estimator, although sample size, the extent of censoring, and shape of distribution affected its relative efficiency. Ignoring unfailed test specimens always led to inefficient parameter estimates. Using the generalised gamma distribution, the censored likelihood technique was used to test the form of the failure time distribution for 9Cr–1Mo steel tubes creep tested at 220 MN m−2and 500°C. For this data set, about 25% of the test specimens were removed before failure had occurred. Results suggested that the failure time distribution is log normal. A wide variety of 3 parameter gamma distributions and the Weibull distribution were also shown to be consistent with these data. This is highly consistent with results from past studies using only uncensored data sets. The removal of the censored observations led to an ill defined distribution.MST/3124

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.149

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractAluminium of commercial purity and alloys containing 1 wt-%Mn or 1 wt-%Mg have been deformed in uniaxial compression at elevated temperatures. Analysis of the mechanical behaviour and the deformation microstructure has enabled the conditions under which dislocations accumulate at the large second phase particles to be identified. For most of the materials, the transition temperature is close to that found in earlier work on dilute aluminium alloys. However, it isfound that manganese in solid solution may significantly raise the transition temperature, and the results are analysed in terms of vacancy–diffusion controlled dislocation climb in alloys.MST/3243

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.158

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractA miniaturised disc bend test technique has been used to measure yield and ultimate load values for high purity aluminium, oxygen free high conductivity copper, and normalised and tempered 2·25Cr–1Mo steel. For each material details of load displacement behaviour were recorded with the test variables disc thickness, punch diameter, and die clearance. Data analysis permitted relationships to be established correlating disc behaviour with results from standard tensile tests. These correlations are discussed in terms of testing variables and the strength and ductility of the materials.MST/3347

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.163

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractFunctionally graded materials can be used in aggressive environments at elevated temperature because they provide the possibility of minimising wastage of materials. Gradation of the volume fraction of hard particles through the layers means that thermal cycling effects are less severe than for many conventional metal–substrate systems. Because such materials may provide resistance to wear and corrosion (by using a corrosion resistant matrix), it is thought that they may have applications to environments at elevated temperatures, in which materials selection involves a compromise between corrosion resistance and high yield strength. The object of the present study was to investigate the erosion resistance of the various layers of a candidate functionally graded material which consisted of WC particles in a Ni–Cr matrix. The performances of the various composite layers were considered separately in order to establish the variation of erosion rates through the graded structure. The effects of temperature, volume fraction of hard particles, and erodent size were investigated in a laboratory simulated fluidised bed erosion rig. Scanning electron microscopy and thickness loss measurements were used to characterise the surfaces following exposure. The results showed that the erosion rate at room temperature was at a minimum at intermediate volume fractions of WC particles. However, this behaviour reversed for erosion with larger particle sizes. Although the thickness losses increased with increasing temperature for all volume fractions of reinforcement particles, a reduction in the thickness loss at the highest temperature studied was observed for exposure to both large and small erodents (600 and 200μm alumina). The results are explained in terms of the transition between erosion regimes for the various graded layers of the material.MST/3276

ISSN:0267-0836    

DOI:10.1179/mst.1996.12.2.171

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor