638 SUMMARY OF CURRENT RESEARCHES RELATING TO 



follows. Given a univariant equilibrium occurring at a temperature 

 f between three phases of concentrations ^i, ^25 </>3) owing to the forma- 

 tion or decomposition on cooling of the phase <^3, according to the 

 reversible and isothermal reaction 



01 -1- 9!)2 ^ 4>3 



an evolution of heat is produced on cooling the amount of which may 

 be estimated by the length of the step at f in the cooling curves. 

 The heat evolution is at a maximum for the concentration ^3 and nil 

 for the concentrations 0^ and 02- If ^^ow curves are plotted showing 

 the variation of these heat evolutions as a function of the concentra- 

 tion, ^1, 02 ^i^cl 03 may be determined by extrapolation. The author 

 emphasizes the extreme importance of the method, and the value of the 

 data which have been obtained by its application to numerous series 

 of alloys. 



Alloys of Nickel and Lead.* — A. Portevin gives the equilibrium 

 ■diagram obtained by the application of Tammann's analytical method 

 to the cooling curves of twelve alloys. The diagram indicates that 

 (1) from 0-0 '07 p.c. nickel, lead first separates from the liquid, solidi- 

 fication of the eutectic occurs at 328° C. ; (2) from 0*07-7 p.c. nickel, 

 crystallisation of nickel takes place along a steep branch of the curve, 

 and is followed by solidification of the eutectic as before ; (3) from 

 7-60 p.c. nickel, the mixture, completely liquid above 1365° C, is com- 

 posed of two non-miscible portions : nickel separates from the nickel- 

 rich layer at 1365° C, the liquid remaining (7 p.c. nickel) solidifies as 

 in (2) ; (4) from 60-100 p.c. nickel, a branch of the curve rising from 

 1365° C.-14S4° C. indicates the separation of nickel from a homogeneous 

 liquid. When the concentration of the liquid falls to 60 p.c. nickel at 

 1365° C. the subsequent changes are as in (3). No compounds or solid 

 solutions are formed, the solid alloys containing more than 0*07 p.c. 

 nickel are composed of nickel and the lead-nickel eutectic. 



L Ternary and Quaternary Vanadium Steels.f — L. Guillet gives an 

 account of Piitz's researches on vanadium steels, comparing the results 

 with those obtained by himself. A description of the author's latest 

 work on nickel-vanadium steels follows, in which increasing amounts of 

 vanadium were added to pearlitic nickel steels near the martensitic 

 boundary. The vanadium appears slightly to increase the tendency 

 towards the formation of martensite; it also raises progressively the 

 maximum stress and elastic limit. To obtain the best properties it is 

 necessary to maintain tlie carbon content low, the nickel as high as is 

 consistent with a pearlitic structure. The industrially useful steels fall 

 within the limits • 1-0 ' 3 p.c. carbon, 2-7 p.c. nickel, and • 1-0 • 3 p.c. 

 vanadium. 



Boron Steels.| — A more complete account is given by L. Guillet of his 

 investigation of six boron steels.§ The ferro-boron used in the pre- 



* Rev. de M^tallurgie, iv. (1907) pp. 814-18 (5 figs.), 

 t Tom. cit., pp. 775-83. 



j Tom. cit., pp. 784-96 (17 figs.). See also Jouru. Iron and Steel Inst., Ixxiv, 

 (1907) pp. 207-18 (17 figs.). § See this Journal, 1907, p. 508. 



