R. I. Jaffee

Oxidation of the platinum-group metals

Abstract Experimental studies of the oxidation characteristics of the six platinum-group metals in relatively slowly moving air at 1000°–1400°C are reported. The results are correlated with recent vapor-pressure studies of the metals in vacuum and thermodynamic and kinetic studies in oxidizing atmospheres. A mechanism involving chemisorption and dissociation of oxygen at the surface is suggested. In the range of 1200°–1400°C, all of the platinum-group metals exhibit linear rates of weight loss in air through formation of volatile oxides. The situation becomes slightly complicated with palladium, because of an initial absorption of oxygen. The linear rates of weight loss determined under the specific conditions investigated at 1400° C in slowly moving air at 1 atm pressure for rhodium, platinum, iridium, ruthenium, and osmium are 6.8·10 −3 , 9.6·10 −3 , 3.1, 1.2·10 2 , and 1.2·10 3 mg/cm 2 /h, respectively. For reasons discussed in the paper, these rates are expected to vary with the partial pressure of oxygen, total gas pressure, and the flow rate of the gaseous environment. More research is needed to establish the mechanism of oxidation and the variation of oxidation rates with these variables.

Constitution and mechanical properties of titanium-hydrogen alloys

Hydrogen forms a beta-stabilized system with titanium, with a beta eutectoid at about 300°C and 44 atomic pct H2. The solid solubility of hydrogen in alpha decreases from about 8 to about 0.1 atomic pct from 300°C to room temperature. Hydrogen has little effect on tensile properties, but decreases notch-bar toughness to a large degree. This latter effect appears to be the result of increased notch sensitivity.

The Magnetic Properties of Ordered Nickel‐Manganese Alloys

Nickel‐manganese alloys containing 20.1 percent, 21.4 percent, and 25.3 percent Mn in the form of Rowland rings were put into an ordered condition by very slow cooling to 380°C, and long annealing at that temperature. Magnetization curves and hysteresis loops at room temperature showed that the 21.4 percent Mn alloy was very soft magnetically, while the 25.3 percent Mn alloy was relatively hard magnetically. The 20.1 percent Mn alloy was magnetically soft, but not so soft as the 21.4 percent alloy. The magnetic properties of the ordered 21.4 percent Mn alloy changed markedly from room temperature to about 120°C. Induction at 30 oersteds decreases very rapidly, and the maximum permeability goes through a sharp maximum at 91°C. Coercive force and remanence also decrease during the same temperature interval.

Relationships between impact and low-strain-rate hydrogen embrittlement of titanium alloys☆

Abstract Hydrogen embrittlement of titanium alloys is generally separated into two types: impact embrittlement, which occurs in alpha-titanium alloys, and low-strain-rate embrittlement, which occurs in alpha-beta alloys. Data are presented which show that either low-strain-rate embrittlement or impact embrittlement can occur in alpha-compound, alpha-beta, or beta alloys depending on alloy composition and hydrogen content. These results suggest that both types of embrittlement are different manifestations of the same basic embrittling process, the rejection of hydride from solution in titanium, and that the type of embrittlement observed is related to the kinetics of hydride rejection. If hydride precipitates rapidly, impact embrittlement is observed. If hydrogen is held in supersaturation, strain-induced precipitation leads to low-strain-rate embrittlement.

Heat treatment, structure, and mechanical properties of Ti-Mn alloys

Ti-Mn alloys were studied in order to determine the factors affecting the mechanical properties of β-stabilized titanium alloys. The principal compositional factors have been found to be solid-solution strengthening, the martensitic transformation, and instability of the β phase. Structural factors, such as grain size and shape, were found to have more influence on ductility and toughness than on strength.

Physical and Mechanical Properties of Rhenium

The fabrication of rhenium metal by powder metallurgy techniques is discussed. The following physical and mechanical properties have been measured and are reported: lattice constants, melting point, electrical resistivity, thermal expansion, spectral emissivity, modulus of elasticity, tensile properties and ductility at room and elevated temperatures, work hardening, recrystallization, grain growth, and oxidation resistance.

Further Studies of the Properties of Rhenium Metal

The thermoelectric behavior of the Pt—Pt-Re thermocouple and the resistance of rhenium to attack by certain molten metals is discussed. In addition, data are presented on the stress-rupture behavior of drawn wire, the tensile characteristics of rolled sheet, the variation of Young’s modulus with temperature, and the effect of specimen size and fabrication method on the work hardenability. Mechanical properties of thoriated rhenium are discussed. This includes data on the effect of thoria in rhenium on tensile properties, ductility, work hardening, and recrystallization.

Structure and Properties of Ti-C Alloys

The mechanical properties of Ti-C and Ti-C-O alloys can be altered by heat treatments to dissolve or reject carbon from solid solutions. The maximum strength is obtained by annealing just below the peritectoid temperature. Quenching from the β-carbide field results in softening. Impact behavior is influenced by the extent of solution of interstitials.

MECHANICAL PROPERTIES OF ALPHA TITANIUM AS AFFECTED BY STRUCTURE AND COMPOSITION

The effects of grain size and shape on alloys of titanium with nitrogen and aluminum have been determined. Increasing α grain size decreases strength and hardness and increases impact resistance. Quenching from the β field produces subgrain markings delineating α plates in Ti-N alloys but not in Ti-Al alloys. This suggests a precipitation from the high nitrogen alloys.

Refractory‐Metal Thermocouples Containing Rhenium

The thermoelectric force developed by the following junctions up to 2200°C has been measured: Re vs W, Re vs Mo, Re vs W‐30Re, and Re vs Mo‐50Re. The thermoelectric force for W vs W‐30Re and Mo vs Mo‐50Re has been calculated. The Re vs W junction develops about 15 mv at 1000°C and may be usable up to 2600°C. Re vs Mo develops about 17 mv at 1000°C; the thermoelectric power is low above 1600°C. The outputs of Re vs W‐30Re and Re vs Mo‐50Re couples are low and change signs at about 1200 and 1800°C, respectively. The calculated outputs of W vs W‐30Re and Mo vs Mo‐50Re are high; the W vs W‐30Re output is nearly linear over a wide range in temperature, and the thermocouple should be useful to about 2600°C. All of these couples must be used in vacuum or in neutral or reducing atmospheres.