Thermal shock response of fine- and ultra-fine-grained tungsten-based materials

Development of Nanostructured Tungsten Based Materials Resistant to Recrystallization and/or Radiation Induced Embrittlement

“…The average size of the dispersoids for TFGR W1.1TiC/H reaches 90 nm in the grain interior and 160 nm at the grain boundaries. 32,35) This indicates that the effect of GSMM is significant for TiC precipitation and its segregation at the random grain boundaries. As the GSMM temperature increases, the average size increases: The average size for W 1.1TiC/HNH with GSMM at 2270 K increases to 160 nm in the grain interior and 390 nm at the grain boundaries.…”

“…The hole formation in the WTiC/H is most likely a result from ejection of fine grains due to accumulation of hydrogen at grain boundaries very close to the specimen surface and insufficient strengthening of random grain boundaries, or insufficient enrichment of TiC at random grain boundaries. 32) Thermal shock tests were conducted by pulsed electron beam heating under the condition of ITER-ELM (EdgeLocalized Mode) like loding, where t (pulse length) = 1 ms, P (heat density) = 1.1 GW/m 2 (¦T (resultant surface temperature increase) µ 2270 K), T base (base temperature) = 373 K, n (repeated pulse number) = 100, by using JUDITH (JUelicher DIvertor Test facility in Hot cells)-1 operating at FZK in Germany. The irradiated region was the central area of the specimen, approximately 4 mm © 4 mm.…”

“…As the GSMM temperature increases, the average size increases: The average size for W 1.1TiC/HNH with GSMM at 2270 K increases to 160 nm in the grain interior and 390 nm at the grain boundaries. 32) In those GSMM treated specimens, the Kurdjumov-Sachs (K-S) orientation relationship is recognized at the interface between the TiC phase and W matrix. ) at ³573 K in the linear divertor plasma simulator PISCES-A at the University of California, San Diego.…”

“…The observed superior properties of TFGR W1.1TiC (/H and /Ar) can be attributed not only to their much finer grain size than that of W/SR and W/R, but also to the modified microstructure where the random grain boundaries in the recrystallized state are significantly strengthened. 32) TFGR W1.1TiC/H with two different oxygen contents of 160 and 850 wppm were subjected to thermal shock tests with JUDITH-1 under the condition of ITER-ELM same as for UFGR WTiC/H (oxygen content: 170 wppm). The result is shown in Fig.…”

Recent progress in R&D on tungsten alloys for divertor structural and plasma facing materials

“…(2) Irradiation with 1 keV H3 containing ~0.8% C did not cause (a) 8 significant blistering but produced small holes on the surface, probably by ejection of grains [32]. (3) The thermal conductivity of W-0.5TiC is considerably lower than that of pure W. The thermal conductivity of W and UFG W-TiC become closer at high temperatures [33,34]. (4) Thermal shock loading under ELM (edge localized modes) conditions as they will happen within the International Thermonuclear Experimental Reactor (ITER) caused cracking in network-like patterns with a maximum depth of 170 µm [34] A new microstructural modification method was developed to strengthen the GBs in the recrystallized state, adjust the grain size and remove the residual pores.…”