Surface damage in ultrafine and multimodal grained tungsten materials induced by low energy helium irradiation

Osman El-Atwani, Birck Nanotechnology Center, Purdue University
Mert Efe, Purdue University
Bryan Heim, Purdue University
Jean Paul Allain, Birck Nanotechnology Center, Purdue University

Abstract

Although tungsten is considered the best candidate as a plasma facing component (PFC) in the divertor region in the International Thermonuclear Experimental Reactor (ITER), severe morphology changes such as cavities, blisters, bubbles and nanostructure formation are expected. Increasing defect sinks in the tungsten microstructure is one of the possible solutions to mitigate the irradiation damage. In this work, helium irradiation at low energy (50 and 200 eV) and temperatures of 600 (threshold of vacancy migration) and 950 degrees C were performed on multimodal and ultraflne grained tungsten prepared by spark plasma sintering and severe plastic deformation (SPD), respectively. The multimodal samples consisted of small grains (300-700 nm size) juxtaposed to larger grains (1-3 gm size). Detachment of the small grains was observed in the multimodal grained tungsten irradiated at 600 degrees C and a fluence of 1 x 10(22) m(-2) due to grain boundary grooving. On the same sample but at 950 degrees C, detachment and nanostructuring of the small grains were observed together with recrystallization of the large grains. Irradiation of the SPD samples at 200 eV and 950 degrees C to a fluence of about 2 x 10(22) m(-2), resulted in nanostructuring of the ultrafine grained shear bands in the microstructure. (C) 2012 Elsevier B.V. All rights reserved.

Discipline(s)

Nanoscience and Nanotechnology