Interfacial interaction of solid cobalt with liquid Pb-free Sn–Bi–In–Zn–Sb soldering alloys

Dissolution kinetics of cobalt in liquid 87.5%Sn–7.5%Bi–3%In–1%Zn–1%Sb and 80%Sn–15%Bi–3%In–1%Zn–1%Sb soldering alloys and phase formation at the cobalt–solder interface have been investigated in the temperature range of 250–450 °C. The temperature dependence of the cobalt solubility in soldering alloys was found to obey a relation of the Arrhenius type c _s = 4.06 × 10² exp (−46300/RT) mass% for the former alloy and c _s = 5.46 × 10² exp (−49200/RT) mass% for the latter, where R is in J mol⁻¹ K⁻¹ and T in K. For tin, the appropriate equation is c _s = 4.08 × 10² exp (−45200/RT) mass%. The dissolution rate constants are rather close for these soldering alloys and vary in the range (1–9) × 10⁻⁵ m s⁻¹ at disc rotational speeds of 6.45–82.4 rad s⁻¹. For both alloys, the CoSn₃ intermetallic layer is formed at the interface of cobalt and the saturated or undersaturated solder melt at 250 °C and dipping times up to 1800 s, whereas the CoSn₂ intermetallic layer occurs at higher temperatures of 300–450 °C. Formation of an additional intermetallic layer (around 1.5 μm thick) of the CoSn compound was only observed at 450 °C and a dipping time of 1800 s. A simple mathematical equation is proposed to evaluate the intermetallic-layer thickness in the case of undersaturated melts. The tensile strength of the cobalt-to-solder joints is 95–107 MPa, with the relative elongation being 2.0–2.6%.     

Phase Equilibria in the Ternary Al–Ti–Pt System. II. Liquidus Surface of the Al–Ti–Pt System in the Compositions Range 0–50 at.% Pt

Powder Metallurgy and Metal Ceramics - The liquidus surface of the Al–Ti–Pt system has been constructed for the first time on the composition triangle based on studies of the structure...     

Determination of the reactivity of cellulose which has been modified by the radiochemical method

Conclusions Under the action of ionizing radiation, technical sulfite cellulose degrades. By changing the radiation dose within the range 3.0–15.0 kGr, it is possible to obtain an assigned degree of polymerization for practically any form of viscose product. No post-effect was observed over a period of 4 months.The molecular weight distribution of the irradiated cellulose is characterized by a high uniformity.Radiation-modified cellulose has an elevated reactivity in viscose formation.Translated from Khimicheskie Volokna, No. 2, pp. 22–23, March–April, 1988.     

Properties of cellulose xanthate solutions which have been subjected to action of γ-radiation

Conclusions In the action of -radiation on solutions of cellulose xanthate, the molecular weight nonuniformity of the polymer in solution is reduced, which is one of the reasons for the anomalous decrease in dynamic viscosity of the solution.The irradiated solutions of cellulose xanthate are characterized by increased homogeneity and stability with time as compared with unirradiated solutions.The considerable decrease in viscosity of cellulose xanthate solutions and the increase in its homogeneity under the action of high energy ionizing radiation present practical interest, since these make it possible to obtain solutions of cellulose xanthate with a comparatively low viscosity at high values of mean degree of polymerization and of polymer content of the solution.Transition of part of the -fractions (DP 50) into -cellulose (DP150 and 200) has been detected, which may be a consequence of radiochemical polymerization (cross-linking) in a solution of -cellulose or -cellulose and -cellulose.Translated from Khimicheskie Volokna, No. 5, pp. 24–26, September–October, 1989.     

Phase equilibria in the titanium corner of hypoeutectic alloys in the Ti-Nb-Si-Al system

Physicochemical analysis methods have been applied to the phase equilibria in the Ti-Nb-Si-Al system in the region of alloys rich in titanium. It is found that the crystallization conditions for hypoeutectic alloys with constant 5 at.% aluminum content control the niobium contents up to 17.5 at.%, for which there are two groups. After the primary crystallization of the β phase in alloys in these groups, binary eutectics are formed with different intermetallic phases. The properties of the alloys are dependent on the phase compositions in the eutectic mixtures. The temperature and concentration stability of the phases have been determined. It is shown that a peritectic reaction may give rise to a second intermetallide phase in alloys approximating to equilibrium as a result of subsequent annealing, which does not affect the structure of the cast alloys.