584 C. II. Mathewson — Metallographic Description 



observed. The structure in this part of the object is similar 

 to that illustrated iu fig. 92 (cf. description of Object No. 16). 

 This specimen, in common with many others, seems to have 

 been cast with a light body of outlying metal corresponding 

 to the blade and from which the latter was wrought without 

 very pronounced change of shape and without the necessity 

 of drastic annealing. Probably this part was momentarily 

 brought to red heat after partial working. 



Object No. 6 (cf. Table I). 



The chisel shown in fig. 14 is one of the most interesting 

 pieces examined, since it is the only one in which distinct 

 evidence of hot working was obtained. This evidence is con- 

 fined to the blade of the chisel and leads to the conclusion 

 that this part was formed by bringing the object to bright 

 red heat (neighborhood of 850°) and hammering both in this 

 condition and during the fall of temperature to a point well 

 below that of redness. A large number of forging experiments 

 were undertaken in order to acquire some familiarity with the 

 structures produced under different conditions. In these 

 experiments, the following factors were varied within reason- 

 able limits ; temperature, previous condition with regard to 

 grain size, degree of homogenization, etc., number and intensity 

 of blows, temperature range of hammering, conditions of 

 intermittent working with reheating, and period of rest at the 

 forging temperature. Presentation of these results is beyond 

 the scope of this paper. Only the structures found in this 

 object and duplicate structures obtained in the laboratory by 

 applying the appropriate treatment will be shown. 



The structure shown in fig. 58 corresponds to a scleroscopic 

 hardness of 14. The spot at which this photo-micrograph was 

 taken is indicated on the diagram at the left, fig. 55, and corre- 

 sponds to a distance of about one inch from the extreme edge. 

 A little further on, the hardness drops a few points and 

 averages 9-10 along the main body of the object, showing that 

 the metal is in a soft condition. It will be noted that the 

 grains shown in fig. 58 are abundantly twinned, of rather 

 uniform appearance, and equiaxed. No lines of deformation 

 are visible and it is evident that the metal has recrystallized 

 after permanent distortion at some stage of its existence. 

 Whether the deformation was effected by cold-working or by 

 forging at a high temperature cannot be foretold from this 

 structure alone, since, in either case, the metal must have been 



