摘要:

AbstractAnaerobic adhesives are single–component acrylic adhesives which cure at room temperature and only in the absence of air. They are widely used in the production of cheap and durable mechanical assemblies. In this paper the compositions of anaerobic adhesives are outlined, and it is shown how the products have evolved over the past thirty years. Their properties are covered, and then related to their applications which include the locking of threaded parts, the retaining of coaxially fitted parts, and the sealing of flanges and pipe connections. Specifications relating to the adhesives and their uses are described, and reference is made to techniques commonly used to apply them.MST/319

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.1

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractMicrostructures and textures have been examined in four different commercially pure aluminium alloys after cold rolling and annealing. A correlation has been established between the density of cube sites in the cold rolled structure and the strength of the cube texture component in the rolling ingots. Examination of the alloys by transmission electron microscopy revealed the presence of a {102}〈201〉texture component, i.e. the cube texture twisted 26°around the transverse axis. The cube crystallites frequently occurred either in bands together with {102}〈201〉oriented subgrains or in the periphery of larger areas of {102}〈201〉. The effect of an inhomogeneous hot rolling texture on the recrystallization texture after cold rolling and annealing has been investigated and no correlation between the high fraction of cube texture in the hot rolled material and the strength of the cube in the sheet could be detected. The effect of dynamic recovery during cold rolling on the recrystallization texture has been examined by rolling at boiling water temperature, room temperature, and liquid nitrogen temperature. The strength of the cube texture component increased and the R–component decreased with increasing rolling temperature. As to the effect of alloy composition, the general trend is that the strength of the cube texture component decreases with, increasing alloy content.MST/217

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.8

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractRecrystallization in a commercial purity aluminium alloy has been investigated. The development of recrystallization texture and the rate of grain growth during the transformation has been followed by selected area channelling patterns in a STEM microscope. It is documented that the volume fraction of the cube texture component increases at a higher rate than the other texture components during the recrystallization reaction. This behaviour is interpreted as a preferential cube site localization effect.MST/218

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.19

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe decarburization and surface oxidation reactions were observed during the decarburization annealing cycle of a 3 wt–%Si regular grain oriented electrical steel. Annealing was carried out at four H2O/H2ratios in the range 0·14–0·7 and three temperatures (787, 843, and 899°C) for time periods of up to 30 min. Gravimetric, chemical, and microstructural analyses indicate that the oxidation and decarburization reactions are kinetically related; e.g. at lower H2O/H2ratios, less total oxidation and decarburization are observed at the higher soak temperatures. This behaviour is reversed as the ambient H2O/H2ratio is increased. The microstructural analysis indicates the presence of an amorphous phase and finely dispersed particles of silica (SiO2) and fayalite (Fe2SiO4) in the scale. These data were analysed on the basis of the transition between internal and external oxidation and the data compared favourably with values predicted by existing theories.MST/139

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.22

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe deformation behaviour of the two phases of three plain carbon dual–phase steels after various treatments has been studied using a scanning electron microscope equipped with a tensile straining stage. The distribution of strains between the ferrite and martensite phases, as well as among the different grains of each phase, was observed to be inhomogeneous. The martensite/ferrite strain ratio, which defines the degree of uniformity of straining between the phases, depends on the microstructural parameters of the steels: it increases with increasing volume fraction of martensite, but decreases as the carbon content of the martensite increases. Tempering at various temperatures causes a decrease in the martensite/ferrite microhardness ratio and hence causes an increase in the strain ratio. The macroscopic strain of the specimen at which the martensite begins to deform was also found to be dependent on the microstructural parameters. Regions of applicability of the existing theories of the strength of dual–phase steels can be estimated according to the deformation condition of the martensite.MST/235

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.28

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractIn this paper, the changes in fracture mode that occur when a phosphorus–doped steel is tempered at temperatures between 150 and 650°C are reported. The primary technique used in the study is high–resolution scanning electron microscopy. It was shown by the results that when the steels were tempered at temperatures<250°C, the fracture was usually of a ductile intergranular type. Large shallow microvoids formed along the grain boundaries and were nucleated on second–phase particles. At temperatures between 250 and 400°C, the fracture mode changed to very brittle intergranular fracture. The fracture proceeded along the grain boundaries with very little evidence of plastic tearing. Since tempering at these temperatures does not cause additional segregation of phosphorus, it can be assumed that the onset of brittle fracture occurs because of the precipitation of M3C carbides along the grain boundaries. It is suggested that the carbides contribute to both nucleation and propagation of the intergranular cracks. It is also shown by the results that the ease with which a grain boundary fractures does not simply depend on the amount of impurity segregation, but also on the structure and orientation of the grain boundary.MST/215

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.34

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe attack on pure nickel, cobalt, and iron in the presence of pure sulphur vapours has been studied in the temperature range between 700 and 1150°C. The formation of liquid sulphides which penetrate along the grain boundaries of the solid metals has been detected. The dihedral angles have been measured as a function of temperature, and the temperature dependence of grain boundary andSolidi/liquid interfacial tensions have been computed. The kinetics of penetration of the liquid phase along the grain boundaries have been established and interpreted using Mullins'analysis.MST/248

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.42

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAlthough significant advances in tool material development have been made to facilitate increased metal removal rates when turning steels and cast irons, no equivalent developments have been made for cutting titanium alloys. In this paper, part of a recent research programme is described in which the principal wear mechanisms of ceramic and cemented carbides (coated and uncoated) used for turning Ti–6AI–4V (IMI 318) and commercial purity titanium are investigated. A significant problem is the generation of rake face temperatures above 900°C at relatively low cutting speeds, i.e. ~75 m min−I, which promote rapid rake face crater wear by dissolution–diffusion. Of all the tool materials tested, it was the‘straight‘grade (WC–Co) cemented carbides which were most resistant to this type of wear. They also offered superior resistance to flank wear induced by attrition. Experiments in which cubic boron nitride was used and comparative tests with TiB2and TiC coated carbides, in conjunction with solubility considerations, suggest that boron–based tool materials have significant potential for combating wear caused by dissolution–diffusion.MST/245

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.47

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA free-cutting 0·08%C steel has been turned dry using uncoated fine–grained cemented carbide tools and both uncoated and TiN-coated (by chemical vapour deposition)T 42 high-speed steel tools. Temperature estimates from the high–speed steel tools show that coating reduces the maximum rake-face temperature by about 125 K over a range of cutting speeds, permitting higher cutting speeds to be used before the onset of cratering. The wear mechanisms and built-up-edge behaviour have been investigated in terms of the tool/chip interface temperature and the relative plasticity of MnS inclusions. Manganese sulphide seems to have a higher affinity for the TiN coating than for the uncoated tools, permitting easier interfacial shear, and reducing contact area and built-up-edge size. With coated tools a built-up cap of workpiece material forms over the cutting edge, protecting it from wear; as a result there is only a small initial improvement in surface finish, but since nose wear is reduced, surface finish is maintained over a longer cutting period than with uncoated tools.MST/212

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.59

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe transformation of rapidly solidified structures during preheating and extrusion has been investigated by using X-ray techniques and transmission electron microscopy. It was found that the rapidly solidified phases are generally unstable at processing temperatures and transform to equilibrium phases upon exposure to temperatures greater than 400°C. Transformation is an order of magnitude faster under the influence of stress during an extrusion cycle. The effect of increasing compact preheat time leads to substantial coarsening of the microstructure, which has an adverse effect on the mechanical properties. The effect of preheat time–temperature cycles has been investigated by comparing the microstructure and mechanical properties of extrudates produced from induction heated compacts (preheat time 4–5 min) and air heated compacts (preheat time 75 min).Significant property improvements are obtained in extrudates produced from rapidly heated compacts. The results indicate that the properties vary significantly if the preheat time–temperature cycles are varied.MST/196

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.1.69

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor