Effects of boron on the creep properties,phosphorus segregation behaviour,and stress relief cracking susceptibility of 1.5% Cr–0.5% Mo steels

The effects of 25 ppm boron and of 0.05% phosphorus on the creep behaviour at 550 °C and on the fracture temperature in the constant load fracture test were tested for a 1.5% Cr–0.5% Mo steel. B and P decrease the creep strength, the rupture elongation is increased by B. B and P lower stress relief cracking susceptibility, however, it is increased at low stress. In the B doped material the rate of P grain boundary segregation is accelerated and the level of equilibrium segregation is somewhat higher, the equilibrium segregation is somewhat lower in the bainitic than in the martensitic structure.     

On the unique solvability of RLCT-networks

In this paper a handy criterion is presented which is necessary and sufficient to check the unique solvability of an RLCT-network.     

Influence of microgravity on the morphology of the directionally solidified front in an alSi alloy

One aim of the experiments carried out in the GFQ during the German Spacelab Mission D1 was to study the influence of convection on the coarsening of secondary dendrite arm spacing in an AlSi 7.0 alloy during normal crystallization at constant velocitiesv _SF and the temperature gradientG _SF with quenching of the residual melt. When, under μg and 1 g conditions, the same temperature gradientG _SF ≈ 16 K/mm and two different velocities (5 and 8 mm/min) were used, dendrite arm coarsening was shown to be lower than in the 1 g reference experiments atv _SF ≈ 5 mm/min and nearly identical with the reference results atv _SF ≈ 8 mm/min. A separation of the different kinds of convection, gravity-driven convection and convection driven by the volume jump, was tried using the coarsening factorM. The influence of gravity convection on the dendrite spacings seems to be high, if the velocity of crystallization is low. This influence fades away, if the velocity is high(e.g., >8 mm/min). This paper is based on a presentation made in the symposium “Experimental Methods for Microgravity Materials Science Research” presented at the 1988 TMS-AIME Annual Meeting in Phoenix, Arizona, January 25–29, 1988, under the auspices of the ASM/MSD Thermodynamic Data Committee and the Material Processing Committee.     

Vinyl polymer analogues of nucleic acids

The preparation and properties of vinyl polymers carrying the bases of nucleic acids as substituents are described. These compounds form specific complexes with complementary polynucleotides, a process which prevents the latter from functioning as templates in the synthesis of polymeric nucleic acid or protein. The uptake and fate of these polymers in mammalian cells grown in culture and in animals are described; these polymers exhibit weak but selective antiviral effects in such systems.     

Charging of radioactive aerosols

The effects of radioactivity on aerosol charging are examined. Coupled differential equations governing the time-dependent positive and negative ion concentrations in the surrounding gas and the mean charge on a particle within an aerosol cloud are developed. The equations are solved numerically for specific cases of current interest and the results compared to available experimental evidence.