Microstructural and micromechanical assessment of aged ultra-fast sintered functionally graded iron/tungsten composites

Journal article

Functionally graded (FG) iron/tungsten (Fe/W) composites are considered for stress-relieving interlayers in tungsten-steel joints, required in future fusion reactors. The macroscopic gradation of the two materials allows relaxation of thermally-induced stresses and hence extend the lifetime of the cyclic-loaded dissimilar materials joints. While many properties, e.g. thermal expansion and strength, of the as-manufactured Fe/W composites are promising with respect to the anticipated application, the temperature-induced microstructural changes and their effect on the material properties remain largely unexplored. Given that the thermodynamic system of FeW contains two types of intermetallic phases, understanding the microstructural changes in the FG Fe/W composites are crucial for long-term operation of fusion reactors. In the present work, the microstructure of ultra-fast sintered Fe/W composites containing 50 and 75 vol% tungsten is studied via electron microscopy (SEM) and X-ray diffraction (XRD) in as-manufactured and thermal aged conditions (300, 500, and 800 °C for up to 72 h). The hardness and modulus of selected composites are measured via nanoindentation, and the fracture toughness of the FeW interfaces is tested via notched micro-cantilever bending tests. The results from microstructural and micromechanical analyses are discussed, and the materials are evaluated for their application in fusion reactors based on the microstructure-to-property relationship.

Authors: Heuer, S; Li, B-S; Armstrong, DEJ; Zayachuk, Y; Linsmeier, CH

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Materials and Design
• Volume: 191
• Article number: 108652
• Publication date: 2020-03-21
• Acceptance date: 2020-03-16
• DOI: 10.1016/j.matdes.2020.108652
• EISSN: 0264-1275
• ISSN: 0264-1275
• Language: English
• Keywords: tungsten-steel composites; nuclear fusion; first wall; functionally graded materials (FGM); multi-scale characterization; FFR; DEMO; micro-cantilever bending; nanoindentation