Effect Of Iron Addition Research Articles

Effect of iron additions on β-phase stability with respect to α″-martensite in V-28Al-17Ti(wt.%)

The effect of iron additions (up to 7 wt.%) on the β b.c.c.-phase stability with respect to α″ orthorhombic-martensite and the corresponding transformation volume change in V-28Al-17Ti (wt.%) alloy has been studied using optical microscopy and X-ray diffraction. It was found that iron additions stabilize the β phase while the volume change remains positive and relatively high (3–4%). Using a liquid nitrogen refrigeration treatment and introducing cracks into the materials to further test β-phase stability, and carrying out a thermodynamic analysis, it was found that an addition of 5 wt.% of iron gives rise to the optimum level of stability of the β phase. This, in turn, should ensure maximum transformation toughening effects when this alloy is used as a dispersed phase within a γ titanium aluminide matrix.

Grain refinement of copper by the addition of iron and by electromagnetic stirring

The effect of iron additions in the range of 0.57 to 7.5 wt pet on the grain size of electromagnetically levitated copper-iron alloys was investigated. The samples were solidified while levitated or quenched in water from the molten state. The addition of iron was found to be effective in reducing the grain size of copper, and the average grain size decreased as the iron content was increased up to the peritectic liquid composition of about 2.8 wt pet Fe. Beyond this composition, the grain size of the samples solidified in the levitated state was insensitive to the iron content, whereas that of the quenched samples continuously decreased with increasing iron content. The results indicate that electromagnetic stirring causes fragmentation of copper dendrites in the hypoperitectic region, and hence enhances grain refinement. In the hyperperitectic region, on the other hand, the stirring has a detrimental effect on the grain refinement by agglomerating the primary iron particles which act as heterogeneous nucleation sites for the copper matrix.

The effect of iron additions on the microstructure and properties of the ?Tribaloy? Co-Mo-Cr-Si wear resistant alloys

The effect of iron additions in the range 5 to 15 wt % iron inclusive on the microstructure and properties of two Co-Mn-Cr-Si wear resistant alloys (“Tribaloys” T400 and T800) has been investigated. Iron additions were found to stabilize the f c c form of the cobalt solid solution, to give a fully eutectic matrix and to decrease the volume fraction of the primary Laves phase. These microstructural modifications have little effect on the plane strain fracture toughness but result in a significant increase in the modulus of rupture. The addition of iron induces only minor changes in the corrosion and oxidation resistance of T800, whereas the performance of T400 deteriorates.

Effect of iron addition on the precipitation behavior of CoNiCr alloys containing Nb

The effect of iron addition on the precipitation behavior of Co-Ni-Cr-Nb alloys is discussed. Iron addition changes the main precipitate from orthorhombic β-Ni3Nb (Ni3Cb) to BCTγ″-phase which is disc shaped and precipitates on {100} matrix planes. The growth ofγ″-precipitate follows the Lifshitz-Wagner theory of diffusion controlled growth. An attempt has been made to analyze the structure ofγ″ using the electronic considerations of the Engel-Brewer theory. On continued aging, metastableγ″ transforms to a stable β-phase on {111} matrix planes. The orientation relationship of this phase is similar to that observed in other alloys. In addition to intragranular precipitation, β=phase also precipitates at the grain boundaries and grows into the grains. The transformation ofγ″ into β-phase does not affect the hardness to any significant extent.

The effect of iron addition on the corrosion resistance and mechanical properties of modified aluminium bronze with chromium addition

The effect of chromium addition both in the presence and absence of iron on the corrosion resistance of the aluminium bronze containing chromium has been further investigated. Maximum improvement in the corrosion resistance in the presence of Fe is brought about by 0.9% chromium and by 0.6% chromium is absence of Fe. Chromium addition brings about more improvements in the corrosion resistance of aluminium bronze in the absence of Fe rather than in its presence. Fe brings about an improvement in the mechanical properties. However, contents exceeding 3.8% result in deterioration of the mechanical properties. A 2% Fe both for addition with 0.9% chromium appears to be a reasonable compromise for improved corrosion resistance and mechanical properties.

The effect of fe additions on the embrittlement of Cu-Bi alloys

The effect of iron additions on the embrittlement of Cu-Bi alloys was studied by monitoring the ductility and grain boundary chemistry of embrittled specimens as a function of iron content. Mechanical properties improved for the same embrittling heat treatment as the bulk iron level increased, and this was correlated with a decrease in bismuth segregation to the grain boundaries. No iron was detected segregated to the boundaries, and several possible mechanisms were proposed to explain the beneficial effect of the iron additions. It was also found that approximately 70 min at 530°C is required to attain equilibrium for segregation of bismuth to the grain boundaries, and a diffusion coefficient derived from this data was found to be reasonable for bulk diffusion of bismuth in copper.

Isolation and properties of individual components of cattle transferrin: the role of sialic acid.

Homozygous cattle transferrin has been fractionated into six main peaks by DEAE-Sephadex chromatography. These correspond to the six transferrin components seen in starch gel electrophoresis of normal serum. In addition, six more minor components were isolated from DEAE-Sephadex, making 12 in all, and these could be divided into six pairs. Treatment of whole transferrin with neuraminidase yielded only two bands. Treatment of the individual fractionated bands showed that the slower band of each pair had the same mobility as the slow band from treated whole transferrin, while the faster band from each pair corresponded with the fast band of treated whole transferrin. These observations, and the results of sialic acid assays, showed that the difference between the pairs of bands was caused by differing numbers of sialic acid residues (0–5) per molecule of protein, but that sialic acid was not responsible for the difference between the bands within a pair. The mode of genetic control is discussed and probably involves three loci. Other physicochemical properties of cattle transferrins, namely, molecular weight, effect of iron addition, and behavior in isoelectric focusing, were also studied.

THE SINTERING OF URANIUM-CARBON-IRON ALLOYS IN THE PRESENCE OF A LIQUID PHASE

The preparation of uranium mono carbide bodies containing ∼1% open porosity and with a density of ∼12·4 g/c.c. by cold compacting and sintering uranium/graphite mixtures is described. The effect of iron additions in producing a liquid phase during sintering has been studied, and it is shown that the addition of 10 wt.-% UFe2 to the stoichiometric mixture of uranium and graphite raises the sintered density to ∼13·1 g/c.c. and reduces the open porosity to ∼0·5%. The mechanism of carbide formation and densification in the presence of a liquid phase is discussed.