Effect of HIP temperature on microstructure and low cycle fatigue strength of CuCrZr alloy

CuCrZr合金の微細組織と低サイクル疲労強度に及ぼすHIP接合温度の影響

西 宏; 榎枝 幹男

Nishi, Hiroshi; Enoeda, Mikio

ITERの炉内機器で用いられるCuCrZr合金について、金属学的欠陥,力学特性、特に疲労強度に及ぼすHIP接合温度の影響を検討するため、溶体化処理後時効硬化させたCuCrZr合金及び980, 1045CのHIP接合を模擬したCuCrZr合金を用いて金属組織観察,引張,シャルピー,低サイクル疲労試験を行った。組織観察の結果、1045C CHIP材では顕著な結晶粒成長が起こっていたが、光学顕微鏡や電子顕微鏡観察ではボイドのような明瞭な金属学的欠陥は認められなかった。また粗大化した析出物がすべてのCuCrZr合金で認められ、この析出物は980Cの再溶体化処理では容易に固溶しないことがわかった。1045C CHIP材の低サイクル疲労強度は他のCuCrZr合金より低く、この原因は1045Cの熱処理中に結晶粒界部の欠陥が生じたためと考えられる。

In order to investigate the effect of the HIP cycle temperatures on the metallurgic degradation and the mechanical properties, especially on the fatigue behavior, observations of the microstructure, tensile test, Charpy impact test and low cycle fatigue test are performed for various heat treated CuCrZr alloys, which were solution-annealed followed by water-quenched and aged state and CuCrZr with simulated HIP cycle at temperatures of 980, 1045 C. Grain growth remarkably occurred on 1045 CHIP CuCrZr, though slightly on 980 C HIP CuCrZr. Metallurgic degradation such as voids was not obviously found by optical and SEM observation. There were coarse precipitates in all the CuCrZr. The coarse precipitates did not go easily into re-solution at temperature of 980 C. The low cycle fatigue strength of 1045 CHIP CuCrZr was lower than that of other CuCrZr. The degradation is attributed to the cracks which were caused by metallurgic degradation in the heat cycle.