Microstructural Characterization of As-cast Hf-B Alloys

Author(s)

Janio Gigolotti, Joao Carlos ; Suzuki, Paulo Atsushi ; Nunes, Carlos Angelo ; Coelho, Gilberto Carvalho

• Document type: Journal article
• Source: MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS; v. 15, n. 2, p. 6-pg., 2012-03-01.

Abstract

An accurate knowledge of several metal-boron phase diagrams is important to evaluation of higher order systems such as metal-silicon-boron ternaries. The refinement and reassessment of phase diagram data is a continuous work, thus the reevaluation of metal-boron systems provides the possibility to confirm previous data from an investigation using higher purity materials and better analytical techniques. This work presents results of rigorous microstructural characterization of as-cast hafnium-boron alloys which are significant to assess the liquid composition associated to most of the invariant reactions of this system. Alloys were prepared by arc melting high purity hafnium (minimum 99.8%) and boron (minimum 99.5%) slices under argon atmosphere in water-cooled copper crucible with non consumable tungsten electrode and titanium getter. The phases were identified by scanning electron microscopy, using back-scattered electron image mode and X-ray diffraction. In general, a good agreement was found between our data and those from the currently accepted Hafnium Boron phase diagram. The phases identified are alpha Hf-ss and B-Rhom(ss), the intermediate compounds HfB and HfB2 and the liquide L. The reactions are the eutectic L double left right arrow alpha Hf-ss + HfB and L double left right arrow HfB2 + B-Rhom, the peritectic L + HfB2 double left right arrow HfB and the congruent formation of HfB2. (AU)

• FAPESP's process: 07/05206-5 - Experimental study of the Hf-Si-B system
• Grantee: Carlos Angelo Nunes
• Support Opportunities: Regular Research Grants