Effects of stress triaxiality and strain rate on the fracture of a CuCrZr alloy

Precipitation hardened Copper-Chromium-Zirconium (CuCrZr) alloy is a prime candidate for divertor components in future European DEMOnstration (DEMO) fusion reactors. To develop the DEMO Design Criteria for In-vessel Components (DDC-IC), the failure criterion of CuCrZr needs to be investigated. Hence, the effects of stress triaxiality and loading strain rate on the fracture of solution heat treated and annealed CuCrZr alloys were studied using digital-imaging-correlation and electron microscopy techniques. It was found that an increase in the stress triaxiality caused a significant decrease of over 50% in the equivalent strain to fracture. On the other hand, increasing applied strain rate from 1.3 x 10(-5) s(-1)to 8.6 x 10(-3) s(-1) had no considerable effects on the yield stress and elongation. However, higher flow stresses and a larger number density of voids were observed under the highest applied strain rate of 8.6 x 10(-3) s(-1). Fracture surface analysis showed that the failure model was dominated by void growth and coalescence for all the tests. This work has been performed within the Engineering Data and Design Integration (EDDI) sub-project of the EUROfusion Materials work package and aimed to contribute to the development of the DEMO Design Criteria for In-vessel Components. (C) 2020 United Kingdom Atomic Energy Authority. Published by Elsevier B.V.

Automated summary

The study found that an increase in stress triaxiality caused a significant decrease in the equivalent strain to fracture for CuCrZr alloy, while increasing the applied strain rate had no considerable effects on yield stress and elongation. Fracture surface analysis revealed that void growth and coalescence dominated the failure model for all tests.