434 SUMMARY OF CUREENT RESEARCHES RELATING TO 



alloys. Two compounds, Cd3As2 and CdAs2 and two eutectics, were 

 identified. In the range 1 to 40 atomic per cent arsenic, crystals of 

 CdgAso were enveloped in the eutectic which was nearly pure cadmium, 

 etching dark with hydrochloric acid while the compound remained bright. 

 The crystals frequently contained inclusions : it was accordingly impossible 

 to ascertain their composition by a separation method. From 40 to 62 

 p.c. arsenic the alloys consisted of the same compound with the other 

 eutectic. In this range considerable undercooling of the melt occurred ; 

 its influence upon the structure is described. 



Copper-aluminium Alloys with 8^ to 90 p.c. Copper. * — H. 

 Hauemann and P. Merica describe in detail the microstructure of the 

 copper-aluminium alloys in the range indicated, when submitted to 

 various treatments. The specimens were etched with ferric chloride in 

 hydrochloric acid, or with ammoniacal copper chloride solution. The 

 velocity of crystallization was found to be remarkably great. Slow 

 cooling in the furnace produced large plates of a and y, and the a y 

 eutectoid was lamellar. More rapid cooling in air caused y to crystal- 

 lize in star-shaped forms, and a as needles, while the eutectoid was also 

 acicular in appearance. When quenched, alloys containing more than 

 88 p.c. copper consisted of needles, those containing 86 to 88 p.c. copper 

 consisted of needles +y, and those containing 84-86 p.c. copper con- 

 sisted of y and /3. A remarkable similarity was found between the 

 structure of the copper-aluminium alloys and that of steel. 



/5-Constituent of the Aluminium-bronzes.+ — The copper-rich 

 aluminium-copper alloys consist, according to their aluminium content, 

 of one or two of the constituents a, jS and 8, ^ being the a -f,8 eutectoid. 

 A. Portevin has found that this eutectoid may exist in either of two 

 forms, a comparatively coarse sponge-like network and a fine lamellar 

 form resembling the pearlite of annealed steel. Both forms may be 

 present in the same specimen, e.g. in the alloy of eutectoid composition. 

 The coarse network form commonly occurs in contact with excess of the 

 a phase, while the fine lamellar form is found in contact with excess S. 

 The author has found numerous examples of eutectics which occur in 

 more than one form, and describes as typical the various forms of the 

 Sb-Cu2Sb eutectic of the antimony-copper alloys. The aluminium- 

 bronze sections were etched with acid ferric chloride in alcohol, or with 

 ammonium persulphate solution, while the structure of the antimony- 

 copper alloys was revealed by simple poHshing. 



W. Guertler+ points out the instructive resemblance in microstructure 

 between the eutectic of the antimony-copper system described by Por- 

 tevin, and the "Ledeburite " eutectic of the iron-carbon system described 

 by Benedicks. Further research on the non-ferrous alloys is revealing 

 complexities analogous to those of the iron-carbon system. 



* Int. Zeitschr. Metallographie, iv. (1913) pp. 209-227 (18 figs.), 

 t Int. Zeitschr. Metallographie, iv. (1913) pp. 257-260 (11 figs.). 

 J Int. Zeitschr. Metallographie, iv. (1913) pp. 261-2 (1 fig.). 



