摘要:

AbstractThe microstructure and solid state phase transformations which take place in aluminium alloys containing lithium have been assessed. In addition to the binary Al–Li system, the Al–Li–Cu, Al–Li–Mg, and Al–Li–Cu–Mg systems are discussed in detail together with the role of dispersoid forming elements. The physical metallurgical basis of current alloy development is thereby established.MST/595

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.81

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe role and construction of steam condensers are reviewed and the factors affecting materials selection are outlined. Comparisons are made between the behaviour of copper-base alloys and commercially pure titanium tubing under test and in service. The implications of a change in tube material on condenser design are reviewed. The potential for using the Ti–6Al–4V alloy for last stage low-pressure turbine blading is also reviewed.MST/598

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.91

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Abstractβ-type titanium alloys offer a unique combination of properties for springs. Their high strength, low elastic modulus, low density, and good corrosion resistance result in springs designed to be both smaller and lighter and more corrosion resistant than springs made of other materials. Design considerations, along with mechanical and fatigue properties, are discussed for a Ti–3Al–8V–6Cr–4Mo–4Zr alloy. Examples of applications are included.MST/597

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.97

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe volume change arising from introducing interstitial carbon and nitrogen into an fcc Fe–Cr–Ni alloy has been studied. The carbon+nitrogen content varied from 0·3 to 1·3 at.-%. To complement these studies, alloys having a constant low-carbon content and a nitrogen content varying from 0;amp;#x00B7;04 to 0·91 at.-% have also been studied. Volume was determined by X-ray diffraction using electropolished bulk polycrystalline specimens. An atom of carbon or nitrogen was found to increase volume by an amount approximately equal to three times its own volume or 70% of the atomic volume of the iron. In contrast with some studies, it was found that nitrogen exceeds carbon in dilating the fcc iron lattice. This occurs despite the atomic volume of carbon exceeding that of nitrogen. This is ascribed to electronic effects and to carbon–iron bonds stronger than nitrogen–iron bonds. A model calculation is given for the dilation.MST/533

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.101

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe main models (mixture laws, finite element methods, self-consistent methods) proposed to describe the stress–strain curve of a two-phase material from the stress–strain curves of its components have been considered. None of these models exactly describes the behaviour of the two-phase alloys (each phase equal vol.-%) studied (Cu–Ag and Cd–Zn).MST/473

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.105

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe propensity of two C–Mn steels (BS3602-490Nb and BS3602-HFS35) to creep crack growth has been investigated, mainly in terms of the notch rupture lifetime. The study was carried out at a typical pipe operating temperature of 360°C. Three casts of each steel were compared and a cast to cast variation was revealed which has been attributed to the variations in hardness level and chemical composition. Uniaxial creep rupture characteristics were also determined and it has been shown that an indication of the notch rupture lifetimes of these steels can be obtained from the short-term uniaxial creep rupture characteristics of the material.MST/534

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.110

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe influence of microstructural variations on the fracture toughness of two tool steels having compositions (wt-%) lC–4Cr–5Mo–2V–6W (AISI M2 high-speed steel) and 0·35C–5Cr–1·5Mo;amp;#x2013;1V (AISI H13 hot-work steel) was investigated. In the as-hardened condition, the H13 steel has a higher fracture toughness than M2 steel, and the latter steel is harder. In the tempered condition, the H13 steel is again softer and has a higher fracture toughness than M2. There is a decrease in fracture toughness and an increase in hardness when the austenitizing temperature is above I050°C for M2 steel and above 1100°C for H13 steel, in both the as hardened and hardened and tempered conditions. The fracture toughness of both steels was enhanced by reducing the grain size and increasing the overall carbide volume in the matrix. The steel samples of average grain diameter≥40μm exhibit 2–3 MN m−3/2lower fracture toughness than samples of average grain diameter≤15μm. A high content of retained austenite appears to raise the fracture toughness of as-hardened M2 steel. Tempering improved the fracture toughness of M2 and H13 steels. The present results are explained using observations of changes in the microstructure and the modes of fracture.MST/468

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.118

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractTensile tests of notched and unnotched Al–6Zn–2·3Mg–1·7Cu alloy bars have been carried out. The underaged and peak-aged unnotched specimens exhibit macroscopic shear localization during testing, followed by shear failure, whereas the overaged unnotched specimens exhibit the conventional‘cup–cone’mode of failure. The introduction of a notch changes the deformation pattern and the fracture mode of the specimens. Deformation is constrained within the notched region, and the triaxial tensile stress developed at the notch results in grain boundary splitting, which complicates the deformation pattern and failure mode. The fracture behaviour of these specimens is explained by an adaptation of crystal slip theory.MST/197

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.125

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe fracture behaviour of a peak-aged, partially recrystallized Al–4·5Cu–1·21Li–0·51Mn–0·20Cd alloy has been investigated as a function of strain amplitude, stress intensity, and environment. It was found that the failure was predominantly intergranular separation, regardless of the environment, stress intensity, or strain amplitude, and that the fracture behaviour was influenced mostly by intrinsic microstructural features, rather than the nature of the environment. The shearable nature of matrix strengthening precipitates, large recrystallized grains, and precipitate-free zones along the high-angle grain boundaries aid in localizing the deformation, resulting in low-energy intergranular fracture. The iron- and silicon-rich intermetallic precipitates in the alloy promote void nucleation following fracture of the particle. A model is proposed which suggests the need for high stresses and strains for the initiation and spontaneous growth and coalescence of microvoids. The mechanisms of fracture behaviour of the alloy are discussed in terms of several concurrent processes involving strength of the material, intrinsic microstructural effects, deformation behaviour, state of stress, and strain.MST/497

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.130

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractIsothermal stress relaxation tests at fixed displacement on coarse-grained laboratory heats of A508-2-type steel, normally highly susceptible to stress relief cracking (SRC), have established that trace impurities are essential for this phenomenon. An undoped heat made from iron containing ~5 ppm sulphur in a high-purity crucible was found to be extremely resistant to SRC. Subsequent chemical analysis showed that this steel contained 2 ppm boron and an inadvertant 66 ppm nitrogen, which presumably scavenged the boron to some extent. Other high-purity heats were doped with boron, sulphur, and phosphorus, singly and in combinations. Boron and sulphur additions were always deleterious; phosphorus sometimes appeared to have beneficial effects. High-resolution scanning Auger spectroscopy confirmed the role of surface-adsorbed sulphur in the cracking mechanism.MST/564

ISSN:0267-0836    

DOI:10.1179/mst.1987.3.2.139

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor