242 SUMMARY OF CUEKENT KESEARCHES . 



Metallography, etc. 



Microchemistry of Corrosion.* — C. H. Desch and H. Hyman have 

 applied the electrolytic methods previously described to two alloys 

 (gun-metals) containing copper, tin and zinc in the approximate 

 proportions 88 : 10 : 2 and 84 : 14 : 2. Each alloy was tested as cast, 

 and also after a heat treatment which altered its constitution. It was 

 found that the amount of corrosion was more affected by small 

 variations of the conditions, especially of the applied electro-motive force 

 and of the state of the surface, than in the case of the brasses. The 

 preliminary removal of the flowed surface layer produced by polishing, 

 by etching with acid ferric chloride solution, eliminated one cause of 

 discordant results, and was more readily attacked than the eutectoid, 

 which was not affected unless the voltage exceeded a certain critical 

 figure. Corrosion was less than that of the brasses under similar 

 •conditions. 



Copper-zinc-tin Alloys. f — O. F. Hudson and R. M. Jones have 

 studied the constitution of brasses containing small percentages of tin. 

 Fifty-two alloys containing ()•;! to 5 p.c. tin and 43 to 09 p.c. copper, 

 the remainder being zinc, were microscopically examined. Nearly all 

 the alloys were annealed below 450° C. for periods of 18 hours to 

 15 days to obtain equilibrium. Some thermal curves were taken. 

 The polished specimens were etched by means of a polish-attack with 

 ammonia. The constituents found were a, /3\ and 8. a a^jpeared 

 reddish-yellow, /3^ bright yellow, and 8 clear light blue. In a number of 

 the alloys all three constituents were present in equilibrium. A 

 diagram is given representing the equilibrium constitution for ordinary 

 temperatures of the ternary alloys containing 50 to 70 p.c. copper and 

 to 5 p.c. tin ; the solubility of tin in brasses and the limits of 

 composition within which the alloys consist of three phases a, jS^ and 8 

 in equilibrium, are defined. 



* .Journ. lust. Metals, xiv. (1915, 2) pp. 189-98 (G figs.), 

 t Journ. Inst. Metals, xiv. (1915, 2) pp. 98-115 (17 figs.). 



