High thermal loads and fatigue in tungsten composites are revealed by researchers

A research collaboration team consisting of Hefei Institutes of Physical Science, Chinese Academy of Sciences and CAS investigated the relationship between property degradation and microstructure evolution in two second-phase dispersion reinforced tungsten materials following electron beam thermal loading.

This research was also published in Journal of Materials Science & Technology.

25 is the ideal environment for survival of human beings. However, the plasma-facing W materials of magnetic confinement nucleus devices are exposed directly to plasma, and typically are subject to steady-state thermal loads between 5 and 20 MW/m² Transient thermal shocks up to 1GW/m²The surface temperature can rise to over 1800°C when tungsten is exposed to the sun. High heat flux loads to W can cause irreversible damage to materials, including surface cracking, surface roughening, and surface melting. It is important to assess the material’s thermal resistance.

Researchers carried out heat loads repeatedly on the Electron Beam Material-research platform (EBMP-30) to test its resistance to 30 kW. The platform was specifically designed to assess the thermal shock resistance (PFMs) of plasma-facing materials.

“It uses a 30 kW weld electron beam with a maximum acceleration voltage 100 kV,” said XIE Zhuoming who built the platform. “It can scan 30 x30 mm.”² Area with a maximum frame rate of 35 KHz and its pulse duration may change between 100 ms and a continuous state.”

Two representative W-0.5wt% ZrCs (WZC), and W-1.0wt% Y were determined using the EBMP-30.₂O₃ Composites made from WYO (Water-Year Oval) were chosen to investigate the damage behaviour resulting from repeated heat loads in steady state with an absorbed power density (APD) of between 10-30 MW/m².

Results show that WZC and WYO specimens’ microstructures, and tensile property do not alter significantly with APD below 20 MW/m². However, APD greater than 22 MW/m²Full recrystallization, grain growth and full recrystallization in WYO specimens.₂O₃ The W matrix was spotted to have particles that were shedding.

Furthermore, WYO’s ultimate tensile strength decreased by 510 MPa to 861 MPa, and by 15% to close to zero respectively.

Due to the different coefficients (CTEs), of the Y,₂O₃ Phase and W. Irreversible plastic deformation occurs in the matrix W. This is especially true around the coarse, Y₂O₃ Wu Xuebang who was the leader of the group, said that particles “lead to the interface between Y and Y”.₂O₃ The W matrix and particles.”

Thermal loads after 22 MW/m²WZC specimens retained a high ultimate tensile force of 816 MPa because they were exposed to high temperatures (1300)

Wu explained that the ZrC particle distribution is uniform and fine, which can be used to compare the CTE of the W matrix. This effectively prevents ZrC particle shed and microcrack formation.

WU stated that the study “reveals the correlations of the microstructure evolution with performance degradation in two second-phase dispersion-strengthened tungsten material samples, as well the mechanism for fatigue damage caused by high thermal loads,” which is an important reference point to further develop high-performance materials.

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Hui Wang and colleagues, Thermal fatigue mechanism and microstructural evolution of second-phase dispersion reinforced tungsten composites subject to repetitive thermal loads. Journal of Materials Science & Technology (2022). DOI: 10.1016/j.jmst.2022.09.007