MIMTMを用いた水銀キャビテーションによる金属の壊食損傷構造

Defect structure of pitting damage of mercury cavitation by MIMTM

義家 敏正*; 佐藤 紘一*; Xu, Q.*; 二川 正敏  ; 直江 崇   ; 川合 將義*

Yoshiie, Toshimasa*; Sato, Koichi*; Xu, Q.*; Futakawa, Masatoshi; Naoe, Takashi; Kawai, Masayoshi*

水銀を陽子ビームのターゲットに用いた核破砕中性子源では、水銀中のバブル崩壊時に発生する衝撃波による、窓材料の損傷が問題となる。材料の損傷機構を解明するために電磁式衝撃圧負荷試験装置MIMTMで衝撃を負荷したNi, SUS304鋼の単一あるいは幾つかの衝撃が重なった変形組織を表面近傍の陽電子消滅分光法と透過電子顕微鏡法により観察した。生成する欠陥構造は、高速圧縮変形装置により負荷した100m/sの衝撃変形と比較して、非常に早い変形を受けていることが明らかになった。

A mercury target in high-power spallation neutron sources is subjected to the pressure wave caused by proton beam. Subsequent formation and collapse of cavitation bubbles lead to cavitation damage on the target vessel, especially the beam window. The cavitation damage in Ni and austenitic stainless steel SUS304SS were studied by using MIMTM (electro-Magnetic IMpact Testing Machine) developed to simulate the damage. The existence of dislocations, stacking fault tetrahedra and vacancies was detected by positron annihilation lifetime measurement in Ni and non-cellar dislocation structures were observed by transmission electron microscopy in Ni and SUS316SS. High density of twins was also observed in SUS304SS. These results were compared with those of high speed compression test by using high speed projectile and proved that the cavitation damage by MIMTM corresponded to high speed deformation.