Effect of undercooling temperature on the solidification kinetics and morphology of Y-Ba-Cu-O during melt texturing

✍ Scribed by B.J. Chen; M.A. Rodriguez; S.T. Misture; R.L. Snyder

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 933 KB
• Volume: 217
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(93)90341-m

✦ Synopsis

The phase content of a series of YBa2CusO,_o ( 123 ) bars was determined as a function of the holding time during the postmelting solidification process at different undercooling temperatures. Quantitative XRD analysis of these samples shows that 123 recrystallization occurs in three distinct stages after cooling from the melting temperature. The first stage is an incubation period during which no 123 forms, followed by a rapid liquid-assisted reaction stage, then finally a slow solid-state sintering stage. Nucleation of 123 from the partial melt which contains 211 +BaCuO2+liquid is a low-probability process which results in only a limited number of nuclei forming during the texturing process. The undercooling temperature is a critical parameter which controls the final morphology of 123 in the case of non-directional solidification. Large amounts of undercooling results in a microstructure characterized by randomly-oriented dendritic needles or plates, while a low degree of undercooling yields large, blocky domains of oriented 123.