ELECTRON MICROSCOPY 



(14). The transformation CuAl. -^ CuAl -^ 

 CU9AI4 -^ CnsAl has been confirmed by se- 

 lected area diffraction. Fig. 18 shows some 

 of these processes: 



(a) corresponds \o k + 6 phases in the 

 phase diagram of this alloy. The microscopic 

 image is structureless and the diffraction 

 pattern shows the structure of a face-cen- 

 tered cubic lattice corresponding to K-phase. 

 The diffuse ring superposed on (200) ring of 

 K-phase suggests the existence of 0-phase. 



(b) shows 77-phase (CuAl) which was 

 taken at 400°C, 100 min after (a). It is ob- 

 serv^ed that the single crystal of ij-phase 



about 1 iJL came out of the micro-grain of 

 0-phase. The diffraction pattern shows the 

 structure of CsCl type. 



(c) shows 7-phase (CU9AI4) which was 

 taken at 450°C, 120 min after (a). In the 

 image, conspicuous change was not observed 

 except that the single crystal plate has 

 grown further. The orientations of 7-phase 

 relative to 77-phase are as follows: 



(i) (114),// (110),, [IlO],// [IlO], 



(ii) (110)^// (110),, [iio],// [110], ■ 



The diagram here shows the latter orienta- 

 tion. 



(a) 





(b) 





(c) 



Fig. 18. Transformation of Al-Cu alloy due to 

 heating in vacuum, (a) Room temperature fc -1- 0- 

 phases; (b) 400°C 7?-phase; (c) 450° C 7-phase. 



Gas Reaction Method 



Gas reaction method makes it possible to 

 observe continuously the process of chemical 

 reaction of a specimen. The construction of 

 this device is almost the same as that of 

 specimen heating device except the mech- 

 anism of gas inlet. 



Construction. Fig. 19 shows the con- 

 struction of the specimen chamber to which 

 the old type gas reaction device (15) is at- 

 tached. The diaphragm (1) faced to the 

 lower side of the condenser lens is of clear- 

 ance of about 0.1 mm0 and its position can 

 be adjusted outside the vacuum by two 

 pairs of rods (2) which are placed perpendic- 

 ular to one another. The diaphragm (3) is of 

 clearance of about 0.2 mm(/) and set tightly 

 into the clearance of the pole piece of the 

 objective lens. The diaphragms (1) and (3) 

 are used for preventing diffusion of gas from 

 the specimen chamber. Reaction gas in the 



Fig. 19. Construction of specimen chamber 

 equipped with old type gas reaction device. 



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