12G SUMMARY OF CURRENT RESEARCHES RELATING TO 



Transformation-point Curve y- to ft- or u-Iron.* — P. Gocrens and 

 H. Meyer give a summary of previous investigations dealing wifch the 

 positions of the critical points A 3 and A 2 in iron-carbon alloys, and 

 describe their own work on six alloys containing 0*16 to 0*78 p.c. 

 carbon, with about 0*23 p.c. manganese and 0*15 p.c. phosphorus. 

 Thin disks were heated to {)50°-li>00° C, cooled to a given temperature, 

 at which they were held for 15 minutes, then quenched in water and 

 microscopically examined. With each series a number of quenchings at 

 temperatures ascending by steps of 10° C. were performed. For each 

 alloy the mean of the two quenching temperatures which gave, 

 respectively, martensite + a little ferrite, and pure martensite, was 

 taken as the transformation point. The transformation temperature 

 falls from '.105° C. in the 0*16 p.c. carbon-steel to 855° C. in that 

 containing 0'54 p.c. In the alloys with higher carbon, the point was 

 not so definitely ascertained. 



Influence of Silicon on the Maximum Solubility of Carbide of 

 Iron in y-Iron.f — C. Schols has taken cooling curves of thirty-one melts 

 classified in four series, containing respectively about 1 • 2, 1 •'">, 1 ■ 9, and 

 2*5 p.c. carbon, the silicon-content varying between and 10 p.c. With 

 all carbon-concentrations the addition of silicon lowers the temperature 

 of commencing solidification, leaves the temperature of final solidifica- 

 tion constant at about 1120° C, and raises the temperature of pearlite 

 formation. Pearlite is no longer formed when silicon-content exceeds a 

 certain percentage, this limit being 5 ■ 6 p.c. for alloys containing 1 ■ 2 p.c. 

 carbon, and \ ' 5 p.c. for alloys containing 1 ■ 5 p.c. carbon. The eutectic 

 halt (1120° C.) appears at low T er carbon concentrations as silicon-content 

 rises, indicating the diminished solubility of carbon in y-iron with in- 

 crease of silicon-content. Pieces of selected alloys were heated to 1140°C, 

 slowly cooled to 1120° C, and quenched after 10 minutes at 1120° C. The 

 microscopical examination of these specimens, together with the cooling 

 curves, enabled the author to ascertain the silicon-content necessary for 

 the formation of eutectic in alloys containing less than 2-2 p.c. carbon, 

 the saturation point of the solid solution of carbide of iron in y-iron 

 when no silicon is present. Eutectic occurred in the 1*2 p.c. carbon 

 alloy when more than 5" 6 p.c. silicon was present. Sodium picrate, 

 which coloured the eutectic brown in the quenched samples, was used 

 for etching, also nitric acid in amyl-alcohol. 



Iron Sulphide-iron System.} — K. Friedrich has re-determined the 

 freezing-point diagram, using more pure materials than those employed 

 by Treitschke and Tammann, and finds some differences. The critical 

 points of iron are somewhat lowered by additiou of sulphide of iron, but 

 are not caused to coincide. 



Iron-nickel System. § — Discrepancies in the results obtained in 

 previous investigations of this system have led R. Ruer and E. Schuz to 

 determine the temperatures of solidification of a number of alloys pre- 

 pared from pure materials. The temperatures of magnetic transformation 



* Metallurgie, vii. (1910) pp. 307-12 (18 figs.). 



t Tom. cit., pp. 644-6 (15 figs.). + Tom. cit., pp. 257-61 (9 figs.). 



§ Tom. cit. pp. 415-20 (7 figs.). 



