Microstructural refinement of cast p-type Bi2Te3-Sb2Te3 by equal channel angular extrusion

The objective of this work was to develop a fine and homogeneous microstructure in cast p-type Bi2Te3-Sb2Te3 using multi-pass equal channel angular extrusion (ECAE). The ranges of independent extrusion variables examined were 450-525 degreesC, extrusion temperature; 0.25-7.5 mm/min, punch speed; and one (route A), two (route B and C), and four (route C and E) consecutive extrusion passes, corresponding to strain of 1.16-4.64. The microstructure was characterized by polarized optical microscopy. Re-crystallized grains between 10 and 30 mum in size were achieved via four passes following a new extrusion route schedule (route E) at an extrusion temperature of 500 degreesC and a punch speed of 2.5 mm/min. Results indicate that ECAE processing is a viable method for grain refinement of cast intermetallic compound materials. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.