Abstract:By using X-ray diffraction technique and electrochemical measurements, the texture growth and its effects on the electrochemical properties have been explored under various cooling rates in rare-earth hydrogen storage alloys. It was shown that: (1) the different texture growth characters were obtained in the rare earth hydrogen storage alloys with various compositions under conventional fast cooling and a columnar structure was formed so that thec-axis of the hexagonal structure was oriented parallel to the cooling plane and a higher capacity was attained; (2) the alloy prepared from rapid solidification exhibits a strong (0002) based pole texture in the surface of alloy sheet, i.e.c-axis texture. Its crytal growth character is consistent well with the alloy MmNi_3.5Co_0.7Al_0.8 which has a columnar structure with very high endurance, and low lattice strain was obtained under controlled conditions including high rate cooling in the casting process for obtaining a columnar structure.

Key words: rare earth hydrogen　storage alloy　texture　rapid solidification　capacity　cycle life