172 SUAIMARY OF CURRENT RESEARCHES RELATING TO 



recrystallized, and showed frequent twinning of the crystals. A sample 

 corresponding to the third type of structure, after similar annealing, 

 had entirely recrystallized, the structure being similar to that of cold- 

 worked copper after annealing. Micro-photographs are given to 

 illustrate these annealing effects. The etching was done with 1-1 

 ammonium hydroxide followed by immersion in hydrogen peroxide. 



Iron-carbon-silicori Alloys.*— J. H. Andrew has taken cooling and 

 heating curves of different iron -carbon-silicon alloys, supplemented by 

 micro-examination of variously treated specimens. The alloys were 

 obtained by melting a pure pig-iron with different amounts of 95 p.c. 

 ferro-silicon. The effect of adding silicon to an iron containing 

 3*5-4 PjC. carbon is to raise the melting-point at first, but further 

 additions lower it, the maximum occurring at 3 p.c. silicon. • The 

 pearlite change-point is rapidly eliminated, and with 4-5 p.c. silicon 

 is not shown in the cooling curves. The Ar2-3 point is also raised, 

 but not so readily. With 10 p.c. silicon it is raised to the freezing- 

 point, and the cooling curve shows but one arrest corresponding to the 

 freezing of the alloy. This would explain the insolubility of carbon in 

 high silicon alloys, the iron being in the a-state, and therefore unable to 

 dissolve carbon. A photo-microgi-aph is given of an alloy containing 

 2 "52 p.c. carbon and 9 '86 p.c. silicon, showing no pearlite, the whole 

 mass being composed of silico-ferrite and free graphite. Other photo- 

 micrographs are given of alloys quenched from just below the freezing- 

 point, which show that even with ternary alloys as high in silicon as 

 10 p.c, carbide (either carbide of iron or carbo-silicide of iron), and 

 not graphite, separates from the melt, and can exist undecomi^osed 

 down to about 1100" C. P>y prolonged anneahng, at 600° C, of an iron- 

 carbon alloy consisting entirely of pearlite, the carbide was progressively 

 decomposed into a-iron and free carbon. The presence of silicon greatly 

 acilitates the resolution of the carbide. 



Structure of Copper-zinc and Copper-tin AUoys.f — In a general 

 review of our knowledge of the constitution of the copper-zinc and 

 copper-tin alloys, the results obtained by the micrographic method of 

 study are set forth in detail by W. Broniewski, and are compared with 

 the results obtained by other methods of study. The cumulative 

 evidence of the results, as a whole, point to the existence in copper-zinc 

 alloys of the three compounds, CuZn, CuZuo, and CuZn^ ; and in copper- 

 tin alloys of the three compounds, Cu^Sn, CugSn, and (JuSn. 



* Iron and Steel Institute Carnegie Scholarship Memoirs, vii. (1916) pp. 1-17 

 (15 figs.). 



t Rev. de Metallurgic, xi. (1915) pp. 961-89 (19 figs.). 



