In the framework of joining processes of Ultra High Temperature Ceramics (UHTCs), sessile drop experiments were performed in the Ni-B/ZrB2 system in the range 1110°≤T≤1200°C. They show that, at temperatures between 1110 and 1150°C, isothermal solid-liquid transitions occur in a sequence; while in fact at T≥1200°C the drop melts without any further phase transition, at lower temperatures complete melting is followed by a solidification stage and final re-melting. This complex behaviour, which can be very relevant when utilizing Ni-B alloys for brazing processes (e.g. by the Transient Liquid Phase Bonding technique), is successfully interpreted on the basis of the complete B-Ni-Zr phase diagram newly computed by CALPHAD: isothermal sections, calculated between 1110 and 1150°C, show that the composition of the drop enters, crosses and leaves the primary solidification region of the Zr2Ni21B6 ternary compound. The use of thermodynamic modelling for the explanation of experimental data sets a link between wetting and joining experiments, and phase diagrams assessment.

Isothermal solid-liquid transitions in the (Ni,B)/ZrB2 system as revealed by sessile drop experiments

ARTINI, CRISTINA;CACCIAMANI, GABRIELE;
2013-01-01

Abstract

In the framework of joining processes of Ultra High Temperature Ceramics (UHTCs), sessile drop experiments were performed in the Ni-B/ZrB2 system in the range 1110°≤T≤1200°C. They show that, at temperatures between 1110 and 1150°C, isothermal solid-liquid transitions occur in a sequence; while in fact at T≥1200°C the drop melts without any further phase transition, at lower temperatures complete melting is followed by a solidification stage and final re-melting. This complex behaviour, which can be very relevant when utilizing Ni-B alloys for brazing processes (e.g. by the Transient Liquid Phase Bonding technique), is successfully interpreted on the basis of the complete B-Ni-Zr phase diagram newly computed by CALPHAD: isothermal sections, calculated between 1110 and 1150°C, show that the composition of the drop enters, crosses and leaves the primary solidification region of the Zr2Ni21B6 ternary compound. The use of thermodynamic modelling for the explanation of experimental data sets a link between wetting and joining experiments, and phase diagrams assessment.
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11567/717996
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 15
  • ???jsp.display-item.citation.isi??? 14
social impact