Mikio Nishihata

Hydrogen embrittlement of cold-worked metastable austenitic stainless steels.

The effect of cold-working on hydrogen embrittlement of metastable austenitic stainless steels has been investigated. The specimens were made of SUS302 and SUS304, which had different austenite stabilities, and were cold-worked by 20% to 80%. Hydrogen embrittlement of H-charged specimens was measured by bend testing. The main results are as follows:(1) The bend deformation resistance decreased due to hydrogen charging.(2) Hydrogen embrittlement depended on Vickers hardness or strain-induced martensite content but not on the type of specimen.(3) The decrease in bend deformation resistance by hydrogen charging was recorvered by keeping the specimen at room temperature.(4) Hydrogen embrittlement did not depend on the amount of hydrogen absorbed. The amount of hydrogen absorbed by SUS302 increased with cold-working, whereas that absorbed by SUS304 decreased with cold-working.(5) Hydrogen charging caused blisters on SUS302 and cracks on SUS304. Blisters tended to be induced on the severely cold-worked specimens and cracks on the mildly cold-worked ones. The difference in surface state between H-charged SUS302 and SUS304 specimens indicated different hydrogen absorption mechanisms for these two steels.

Effect of Vickers Impression and Strain Rate on Mechanical Properties in Copper Alloys for thin leaf springs

金 属材料 の 強度 に及 ぼす要 因 として は, 金属組 織, 残 留応 力, 不均 一層 な どの微 視的 な もの と, 加 工上 か ら生 ず る内部, 表面 の比 較的 に大 きいキ ズな どと試験 条件 か ら生 ず る温度 お よび歪 速度 な どが あげ られ る. と くに, 疲労 強 さな どは前 者 の微視 的 な ものに敏 感 で あるが, 静的 強度 には影響 が少 な い とされ てい る. こ こで は, 静的 強度 と巨視 的欠 陥 の関係 を 明 らか に す る 目的 で, キ ズの モデル として ビ ッカース圧 こんを 設 け, そ の大 き さ, 方 向, 位 置 な どが 薄板銅 合金 ばね の引張 強 さ, 伸 び, 破断 形状 に どの よ うな影 響 を示す か につ い て検討 し, 併せ て, 歪 速 度の 影響 につ いて も 検 討 した もの であ る.