562 C. H. Mathewson — Metallographic Description 



details of a given operation, i. e., the number and intensity of 

 blows, size of hammer face, etc., in hammering; the speed, 

 number of passes, etc., in rolling, would also influence the 

 final result. There are so many of these variables that it is 

 doubtful if the structural effects can ever be sufficiently 

 distinctive to permit a clear interpretation of the contributing 

 factors. 



The appearance of these lines of deformation may be seen 

 in fig. 62, which represents the effect of continuous forging 

 from red-heat down to ordinary temperature on an initially 

 coarse recrystallized grain. Partial recrystallization in the 

 form of fine grain has occurred during the early stages of the 

 work at high temperature, but a large number of the original 

 grains have remained and these are traversed by dark markings, 

 mostly curved or wavy. These are positive evidence of the 

 strained condition. In fig. 48, the deformational alteration of 

 a cast structure may be seen under a magnification of 220 X- 

 Part of the metal has recrystallized owing to light annealing 

 treatment, but large patches of strain-hardened material may 

 be seen; one in the upper right hand corner and another near 

 the center of the left edge, in which the dark lines of deforma- 

 tion give a crevassed appearance. Other structures which show 

 lines of deformation and, therefore, indicate drastic mechanical 

 treatment subsequent to the last anneal are as follows : figs. 

 56, 57; figs. 75, 77; figs. 89, 92, and fig. 97. 



When the character of the deformational treatment has been 

 such as to produce marked elongation of the specimen, the 

 grains themselves show elongation. This is also an effect which 

 cannot be used in formulating quantitative conclusions, since 

 the elongation of the grains is not strictly proportional to the 

 elongation of the mass but varies with their size and distribu- 

 tion. In an ordinary rolling process, such elongation can 

 usually be distinguished when the reduction in area of section 

 reaches some 25 per cent. The structures shown in fig. 62 

 and fig. 75 illustrate this condition. It is hardly necessary 

 to remark that annealing removes all evidence of this character. 



Diffusional Characteristics. 

 All cast bronzes differ internally in composition from point 

 to point. Homogenization is effected by annealing treatment. 

 Portevin (21) was able to effect complete homogenization of 

 a bronze containing 95 per cent copper by annealing for a 

 period of three hours at 750°, while a six-hour period at 400° 



