784 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Quenching and Tempering- of Iron and Steel.* — E. Maurer has 

 quenched a number of steels of varying carbon content, at temperatures 

 800-1100° C, and reheated each sample successively at temperatures 

 rising from 100-750° C. After each heating, the structure, physical 

 properties, and chemical condition of the sample were studied. Some 

 physical measurements were also made on pure iron. The author 

 inclines to the view that in an etched section, whatever the reagent 

 used, martensite normally appears white. Only when the transforma- 

 tion to troostite has commenced does martensite assume a darker colour 

 than austenite. Among the author's conclusions are the following : (1) 

 the effect of quenching on the physical properties of pure iron is due to 

 deformation of a-iron ; (2) homogeneous austenite may be obtained by 

 rapidly quenching high carbon steel containing sufficient manganese ; f 

 (3) austenite changes directly to troostite between 150° and 250 c C, or 

 at higher temperatures when much manganese is present. In mixtures 

 of austenite and martensite, the change first begins in the martensite, 

 but proceeds more slowly than in the austenite. Cooling (as in liquid 

 air) causes austenite to be transformed into martensite, 



H. le Chatelier $ remarks that Maurer's work on the constitution of 

 quenched steels is possibly the most important since Osmond's first 

 investigations. The changes which take place when a quenched steel is 

 heated are : — 1. Mechanical (removal of elastic strain). 2. Physical 

 (change in size of grain, change of troostite into pearlite, removal of 

 cold work effects). 3. Chemical (transformation of austenite and of 

 martensite into troostite). A mathematical treatment of the problem of 

 rate of change of physical properties with temperature, is attempted. 



Alumina for Polishing.§— Aluminium alloyed with a little mercury 

 is readily oxidised in air or water. Robin utilises this property in the 

 preparation of powder for polishing. Strips of pure aluminium foil are 

 shaken up with mercury and are then exposed to moist air. White 

 tufts of alumina form on the surface and may be observed to grow. 

 After about four hours no further oxidation takes place. The alumina 

 thus produced may be used for final polishing without further prepara- 

 tion. It does not appear to be better than that obtained by lengthy and 

 laborious levigation methods, but is speedily and easily prepared in 

 quantity at a small fraction of the cost. 



Heat-treatment of Muntz Metal.|| — G. D. Bengough and O. F. 

 Hudson supplement their former paper If by the results of impact and 

 other tests. The Izod test is not considered to be sufficiently discrimi- 

 nating to give useful information about this alloy. Four types of 

 structure are distinguished :— (1) the rolled ; (2) the island ; (3) the 

 network ; (4) the cast type. The effects of cold work appear to persist 

 even after long annealing at a high temperature. 



* Rev. Metallurgie, v.' (1908) pp. 711-50 (65 figs.). 

 t See this Journal, 1908, p. 394. 



X Rev. Metallurgie, v. (1908) pp. G43-7. § Tom. cit., pp. 751-7 (8 figs.). 



[1 Journ. Soc. Cbem. Ind., xxvii. (1908) pp. 654-8 (11 figs.). 

 1 See this Journal, 1908, p. 262. 



