ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 667 



Widmanstatten Structure in Forged Steels.* — A. Portevin and 

 V. Bernard point out tliat the conditions favourable for the production 

 of the Widmanstatten structure in steel, long heating in the 7 iron or 

 solid solution range, followed by a sufficiently rapid separation of the 

 ferrite during cooling, often occur in the manufacture of forged pieces 

 of steel. A considerable number of forgings examined by the authors 

 to ascertain the cause of their failure in service have been found to 

 possess this structure. Mechanical tests also indicated decided brittle- 

 ness, and the authors conclude that the Widmanstatten structure is 

 commonly accompanied by l)rittleness. 



Life-history of Pro-eutectoid Cementite.f — H. M. Howe and A. CI. 

 Levy have microscopically examined two steels containing respectively 

 I'li and 1"45 p.c. carbon, after different heat treatments. Small 

 specimens were heated to about 1200° C, cooled slowly to determined 

 temperatures, and quenched. Others were heated to 1000° C, quickly 

 cooled to 800° C, and quenched after being held at that temperature 

 for a determined length of time. The form and amount of cementite 

 observed in the specimens led to the following conclusions. In cooling, 

 the coalescence of the pro-eutectoid cementite into readily visible masses 

 is very slow, but is less slow as the carbon content of the steel is greater. 

 The internal pro-eutectoid cementite coalesces more slowly than the 

 network cementite. Internal cementite may be transferred to the net- 

 work, probal>ly by solution and reprecipitation. 



Crystalline Growth of Ferrite. J — A. Sauveur subjected a specimen 

 of steel containing 0"05 p.c. carbon, previously slowly cooled from 

 1000° C, to a high load in the Brinell ball test, and then annealed the 

 specimen for seven hours at 650° C. A vertical section through the 

 bottom of the cavity showed a very coarsely crystalline layer some dis- 

 tance below the bottom of the cavity, while the structure both above 

 and below this layer was comparatively fine. Numerous other experi- 

 ments on the same material confirm the existence of a critical stress 

 (either tension or compression) producing a critically strained condition, 

 which on annealing at temperatures below the thermal critical range 

 develops an excessively coarse crystalline structure. If the strain is 

 greater or less than this critical value, subsequent annealing does not 

 develop a coarse crystallization. The tensile stress required to produce 

 the critical strain in the material investigated was about 22 tons per 

 square inch. 



Slag Enclosures. §—W. Rosenhain, in the official report on this 

 subject, summarizes and discusses the investigations of the last three 

 years. Further work appears to be desirable upon the equilibrium of 

 the system Fe-Mn-S, upon the solubility of oxides of iron, and of sili- 

 cates and sulphides, in iron at various tempera tui-es and also in each 

 other, and upon the mechanical effects of enclosures. 



* Rev. Metallurgie, ix. (1912) pp. 544-50 (8 figs.). 



t Proc. Int. Assoc. Testing Materials, ii., No. 13 (1912) 14 pp. (34 figs.). 



+ Proc. Int. Assoc. Testing Materials, ii., No. 11 (1912) 12 pp. (14 figs.). 



§ Proc. Int. Assoc. Testing Materials, ii,, No. 10 (1912) 22 pp. (4 figs.). 



