ELECTRON IVIICKOSCOI'Y 



Fig. 24. Dislocation arrangements in fatigued 

 aluminum: loops of condensed vacancies and ir- 

 regular dislocation shapes resulting from climb. 

 (Segall and Partridge,'^^ Courtesy Philosophical 

 Magazine) 



Fig. 25. Crystal grain containing twins grow- 

 ing in incompletely polygonized surroundings in 

 nickel. {Bellman,*^ Courtesy Institute of Metals) 



ment of old grain boundaries at low de- 

 formation. 



A study on the formation of precipitates 

 in Al-Ag alloy has been made by Funkano 

 and Ogawa (47). A review on precipitation 

 phenomena has been given by Nicholson, 



Thomas and Nutting (48), (Fig. 26) who took 

 a cine film showing the formation and dis- 

 solution of precipitates. 



Eutectic structures have been studied in 

 SnPb by Takahashi and Ashinuma (49) and 

 on pearlite by Nishiyama et al. (50). 



Studies of Silcox and Hirsch (mentioned 

 in (27)) on radiation damage in copper show 

 the production of condensed vacancy loops 

 and the growth of these loops with higher 

 neutron doses (Fig. 27). Wilsdorf (51) has 

 shown similar effects in neutron irradiated 

 nickel. 



Anti-phase domains in a CuAu-alloy and 

 in AuCuZn-alloy have been studied by 

 Ogawa et al. (52, 53) and in CuAu by Glossup 

 and Pashley (54). CuAu II shows a super- 

 lattice, with layers of copper and of gold 

 atoms stacked on each other in the (001) 

 direction while the sequence changes every 

 five elementary cells in the (100) direction, 

 so that phase boundaries are regularly 

 spaced every 20 A. The formation of these 

 domains was directly observed whilst the 

 specimen was heated (Fig. 28). This work is 

 reviewed by Pashley and Presland (55). 



Observations on martensitic transforma- 

 tions in thin films of iron alloys have been 

 published by Nijama and Shimizu (56) and 



Fig. 26. Guinier-Preston zones in Al-4%-Cu. 



304 



