'82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Metallography, etc. 



Cohesion of Steel.* — Assuming that resistance to deformation is 

 due to simple friction, and that the coefficient of friction is independent 

 of the load, G. H. Gulliver calculates the ratio of the yield-point in 

 tension to the yield-point in compression, for mild steel, as 0*705 to 1. 

 Experimental results give a ratio nearer to unity. Assuming, further, 

 that a cohesive force acting between the metallic particles gives rise to a 

 frictional resistance which may be added to that due to the effect of the 

 external load, the author deduces the value of this cohesive force to be 

 3 • 384 times the stress which corresponds with the tension yield-point. 



Function of Chromium and Tungsten in High-speed Tool-steel.t 

 C. A. Edwards has made hardness tests, cutting tests, determinations 

 of thermal critical ranges, examinations of microstructure, and tempering 

 experiments on two series of iron-carbon-chromium-tungsten alloys 

 (sixteen samples). The composition of one series was approximately 

 C 0-65, Cr6'0, W3 to 19 p.c, that! of the other series CO'65, W 19, 

 Cr 1 to 8 p.c. The author concludes that the critical point at about 380°C, 

 existing in steels with more than 3 p.c. chromium and 6 p.c. tungsten, 

 is a change occurring in a carbide of tungsten which is slowly formed 

 at about 1200° C. At 1320° C. or above, a double carbide of chromium 

 and tungsten is formed, and no low critical point is found. The function 

 of the chromium is the formation of the double carbide. 



Test of Plates from an Old Boiler.:}: — M. Longridge gives details 

 of tests of material cut from a boiler which had been in continuous use 

 for 72 years. The iron plates were found to be extraordinarily brittle, 

 and could be broken up with a hammer. 



Copper-aluminium Alloys. — After briefly reviewing the earlier 

 work, including his own, L. Guillet § discusses the equilibrium diagrams 

 obtained by Carpenter and Edwards, || and by Gwyer.f The author 

 questions the assumption, almost universally made, that a maximum in 

 the curve always corresponds to a definite compound. He supports 

 Gwyer in asserting the existence of CuAl and denying that of Cu 4 Al. 

 The position of the transformation points, and the constitution of the 

 quenched alloys, are still undecided. 



Hardness of Constituents of Alloys.** — Ziegler describes an 

 optical method for measuring relative hardness. When a section is 

 polished on a soft body such as thick cloth, the harder constituents are 

 left more in relief, and the relative hardness is indicated by the 



* Proc. Boy. Soc. Edin., xxviii. (1908) pp. 374-81 (2 figs.), 

 t Journ. Iron and Steel Inst., lxxvii. (1908) pp. 104-32 (37 figs.). 

 X Mechanical Engineer, xxii. (1908) p. 305 (2 figs.). 

 & Rev. Metallurgie, v. (1908) pp. 413-24 (3 figs.). 



|| See this Journal, 1907, pp. 755-6. f Op. cit. 1908, pp. 260-1. 



** Rev. Metallurgie, v. (1908) pp. 565-70 (2 figs.). 



