Effect of HIP at 1000–1200 °C on microstructure and properties of extruded Be-Ti composites

Abstract

Solid titanium beryllide blocks will be used for neutron multiplication in the helium-cooled pebble bed (HCPB) blanket concept of EU DEMO. A combination of hot extrusion of Be-Ti powders and subsequent hot isostatic pressing (HIP) of the obtained Be-Ti composites has been proposed for manufacturing such blocks. This work is devoted to the study of the effect of HIP at 1000–1200 °C on the structure and properties of Be-Ti composites in order to optimize the HIP parameters. The HIP at 1000–1200 °C resulted in an almost single-phase titanium beryllide (TiBe12) with small amounts of Be and other phases, which gradually dissolve with an increase in the HIP temperature. Such a treatment at 1000 and 1100 °C provides a very fine-grained microstructure of TiBe12 with an average grain size of 0.3 and 0.6 μm, respectively. The resulting titanium beryllide is characterized by high microhardness of 1350–1480HV0.1 depending on the HIP temperature. According to the nanoindentation tests of the Be-Ti composite after HIP at 1100 °C, the indentation modulus of TiBe12 can be estimated as 295GPa. The fracture toughness of the TiBe12 was determined as 1.5–1.7 MPa·m1/2. The temperature of 1100 °C was chosen as optimal for the HIP of Be-Ti composites after hot extrusion. The titanium beryllide obtained in this way was used to manufacture a reduced size mockup of Ø20mm × 18 mm. The mockup has no visible surface defects and can be used for further experiments.