350 SUMMARY OF CUERENT RESEARCHES RELATING TO 



Metallography, etc. 



Copper-zinc-tin Alloys.* — 8. L. Hovt aud P. H. M. P. Briuton 

 discuss the nature of the grey constituent formed by adding tin to the 

 brasses. It is probably not a ternary phase, but a phase belonging to one 

 of the binary systems. 



Ball-test on Cast Metals and Alloys.t— The properties of a metallic 

 crystal are different in ditferent directions relative to its crystalline 

 orientation. A. Portevin has studied the variation of mechanical pro- 

 perties with direction by determining the form of Brinell l)all impressions 

 made on single crystals, or on a number of similarly oriented crystals, 

 seen in polished and etched sections. The specimens had been slowly 

 cooled from the liquid state, in order to develop a coarse crystallization. 

 The impressions were generally square, with rounded corners, or oval ; 

 their measurements relative to the dendritic directions are given for two 

 specimens of copper containing respectively small amounts of vanadium 

 and aluminium, and for antimony, iron, zinc, brass, and a copper-tin 

 alloy. 



Metallic Crystal Twinning- by direct Mechanical Strain.| — C. A. 

 Edwards describes experiments made in order to determine whether 

 the acicular markings formed on the surfaces of tin and zinc by 

 mechanical strain are twin crystals or merely appearances which do not 

 extend below the surface. The specimens were cast on polished steel 

 surfaces, previously heated to about 150' C. A gentle pressure was 

 applied to the upper surface of the liquid Ijy means of another piece 

 of polished and heated steel. The specimens were etched, examined for 

 twin crystals, and then strained. Twin markings were formed more 

 readily when the surface was strained in compression than when it was 

 strained in tension. A layer of appreciable depth was removed from the 

 surface. This was done by immersing the specimen in strong acid, 

 since any mechanical method — even the lightest rubbing on the finest 

 emery-paper — caused very serious disturbance of the crystal structure. 

 After the attack by acid the surface was polished on chamois leather, and 

 etched as before. It was found that the twin markings formed on the 

 original strained surface persisted after the removal of the surface layer, 

 indicating that twinning had actually occurred as an effect of mechanical 

 strain alone. 



Structure of High-speed Tool Steels. § — In the course of an in- 

 vestigation into the effect of chromium and tungsten upon the hardening 

 and tempering of high-speed tool steel, C. A. Edwards and H. Kikkawa 



* Jouni. Inst. Metals, xiv. (1915, 2) pp. 178-83 (6 figs.), 



t Rev. Metallurgie, xii. (1915) pp. 95-100 (2 figs.). 



X Jouru. Inst. Metals, xiv. (1915, 2) pp. 116-44 (21 figs.). 



§ Journ. Iron and Steel lust., xcii. (1915, 2) pp. 6-46 (30 figs.). 



