Showing papers in "International Journal of Materials Research in 1992"

Stable and Metastable Equilibria in the Fe - Zn - Al System at 450 °C

Abstract: The reaction of Fe-Al alloys with Zn-Al baths for times counted in days at 450deg C gives a Fe-Zn-Al ternary diagram which differs from the previously observed diagrams after galvanizing iron alloys in zinc baths within minutes. The main differences between the two kinds of diagrams lie mainly in the fact that the solubility of Al in the [delta]-FeZn[sub 9] intermetallic compounds is lower in the long-time diagrams than in the short-time diagrams and in the apearance of a new ternary phase with a composition around Al[sub 6]Fe[sub 8]Zn[sub 86] being isomorphic with the binary [Gamma][sub 2]-FeZn[sub 4] compound. Continuous solid solution between these two compounds is likely, but hard to observe experimentally. (orig.).

Correlation Between Dundurs’ Parameters and Elastic Constants

Abstract: The correlation between the four elastic constants of two adjoint isotropic materials and Dundurs' parameters {alpha} and {beta} is elucidated. Whereas {alpha} is a function of elastic moduli alone, {beta} depends on Poisson's ratios in addition to the elastic moduli. The linear dependency of {beta} on {alpha} is explicitly derived in this work. From these {alpha}-{beta} relationships it can be determined whether or not the assumption of negligible {beta} values is applicable for a given material combination. These figures are powerful means for the design of composites and provide information about which elastic properties of the components are required for obtaining certain Dundurs' parameters. The method is demonstrated for two metal/ceramic systems. (orig.).

Secondary Hardening in High Speed Steels

Abstract: Analyse par sonde atomique et microscopie ionique a emission de champ des precipites de carbures secondaires dans six aciers rapides de differentes compositions. Determination de la taille et de la composition chimique des precipites en fonction de la composition des aciers

Extension of Measurements of the Tensile Flow Stress of High-Purity α-Iron Single Crystals to Very Low Temperatures

Abstract: Measurements on the flow stress of high-purity α-Fe single crystals, carried out by successive tensile deformation steps at different temperatures and combined with stress-relaxation tests, were extended to about 4 K. The temperature dependence of the flow stress down to the lowest temperatures can be described very well by Seeger's theory of kink-pair formation in screw dislocations and an Arrhenius equation with an almost constant preexponential factor

Nucleants in grain refined aluminium after addition of Ti- and B-containing master alloys

Abstract: Nucleation sites for aluminium grains after addition of different types of Al-Ti B master alloys to pure aluminium have been studied. In the master alloys used the Ti/B-rations (wt.%) were 2.6/1.4, 4.8/1, 5.3/0.1, and 6.2/0.03. Specimens were taken after different contact times at 775deg C. The phases involved were identified by powder X-ray diffraction. Phase morphologies in master alloys and in diluted samples were studied by scanning electron microscopy in combination with energy dispersive spectrometry. The observations are discussed and related to possible grain refining mechanisms. (orig.).

Experimental investigation and thermochemical assessment of the system Cu-Y-O

Abstract: Experimental investigations of the thermochemical properties of the phases in the system Cu-Y-O by means of DTA, EMF, TG and calorimetric measurements are reported. The results together with critically selected data from the literature are used for a complete assessment of the Gibbs energies of the ternary phases (based on the Standard Element Reference State, SER). For the binary subsystems critically assessed data from the literature are used

Texture and mechanical anisotropy in cold rolled and annealed pure Ti sheets

Abstract: Hot rolled bands of pure Ti obtained by thermomechanical treatments were old rolled by varying rolling reductions between 50 and 90%. By annealing these specimens at 750degC for 1h, the effect of cold rolling reductions on the development of the annealing texture was systematically investigated with the crystallite orientation distribution function analysis. Also yield stresses and r values of these specimens were determined and their anisotropies were correlated with their textures. It was found that the main orientation of the annealing texture was always (anti 1013)(1anti 210). It increased significantly with increasing rolling reduction up to 80%. At higher rolling reductions, it decreased remarkably. Both yield stresses and r values of these specimens showed pronounced anisotropies, giving minimum values at the rolling direction, and increasing linearly with increasing angle to the rolling direction. By using Sachs' model of polycrytal deformation and by assuming only prismatic slip as the deformation mode, these anisotropies were predicted from the orientation distribution functions of these specimens. Anisotropies of the yield stress calculated with this method agree qualitatively well with those observed experimentally. However, disagreements between calculated and observed anisotropies of r values were considerably large. It was calculated that, since r values were measured after tensile straining of about 10%, contributions of twinning cannot be neglected in the calculation. (orig.).