428 SUMMARY OF CDRRF.NT RESEARCHES RELATING TO 



sidered together with their properties accord with the amorphous cement 

 theory. Cold drawing elongates the crystalline grains owing to plastic 

 deformation, so that the structure appears fibrous. The slipping along 

 cleavage planes within each grain which occurs during deformation 

 decrystallizes the material along the internal surfaces of movement. 

 These amorphous layers are harder and stronger than the crystalline 

 material from which they are formed. When the rigidity of the metal 

 is decreased by heating, recrystallization of the amorphous material 

 takes place with consequent softening of the metal. 



Influence of Arsenic on Brass.* — With the object of determining 

 to what extent arsenical copper such as scrap shell driving bands could be 

 used in the manufacture of brass, the influence of arsenic 'on lirass has 

 been studied in detail by 0. Smalley. The alloys examined consisted 

 of a and a^ brasses with arsenic varying in amount from to I'O p.c. 

 In the case of the a/S brasses, while the strength and hardness are 

 practically unaffected, there is a serious drop in ductility in both the 

 cast and hot-rolled states as the arsenic content rises. This is particu- 

 larly marked in regard to the alternating impact number, which shows 

 a very sadden drop with but small amounts of arsenic. Comparing the 

 results of mechanical tests for the cast and hot-worked states, while iiot- 

 working non-arsenical aft brass raises the ductility and impact number 

 without imparing the tenacity, the effect on arsenical a/3 l)]-asses is to 

 lower the ductility considerably and raise the tenacity only slightly. 

 The embrittling effect of arsenic on a/S brass is due to its existence in 

 the brass as a brittle arsenide, seen in the microstructure as granules 

 distributed in chain-like fashion mainly in the /3 constituent. 



In the case of the cast a brasses, those with small amounts of arsenic 

 (under O'lO p.c.) show superior mechanical qualities to the non- 

 arsenical brass. Further increase in the arsenic content reduces the 

 elongation and shock-resisting properties considerably. All the cast 

 alloys, however, were easily cold-rolled. The effect of cold-working and 

 subsequent annealing causes an all-round improvement in properties up 

 to 0'5 p.c. arsenic. Photomicrographs of arsenical a brasses in the 

 cast, cold-worked and annealed states are given iind described. It has 

 been ^hown that copper arsenide is soluble in the a phase, but its solu- 

 bility is dependeiit upon the rate at which the alloy is cooled, and the 

 improvement in all-round properties of alloys containing 0-2-0"5 p.c. 

 arsenic after cold working and annealing is due to the passage of 

 residual free arsenide into solution. When the arsenic content 

 exceeds 0-5 p.c. it is able to exert its individual embrittling effect, even 

 although in solution. The ease with which cast a brasses can be cold- 

 rolled, despite the presence of granules of brittle arsenide, is explained 

 by the readiness with which the ductile a phase accommodates itself to 

 plastic deformation. The temperature of annealing for arsenical brasses 

 is SC-OO" higher than for similar non-arsenical brasses. 



For etching arsenical brasses, a double attack was found to give more 

 satisfactory results than attack by a single re-agent. After cleaning the 

 polished surface from grease and dirt, it is immersed in a solution con- 



* Jouni. Soc. Chem. Industry, xxxvi. (1917) No. 8, pp. 429-39 (16 figs.). 



