The protium absorption-desorption properties of Ti-V-Cr-(Mn, Ni) alloys were investigated in conjunction with Mn, Ni and V contents and heat-treatment conditions. The compositions studied were (1) Ti-35V-(37-x)Cr-xM (M=Mn and Ni; 0 ≤ x ≤ 15), and (2) Ti-xV-Cr-M (M=Mn and Ni; 15 ≤ x ≤ 45) in which the content of Ti, Cr, and M was fixed at a ratio of 28 : 32 : 5. The addition of Ni reduced the protium storage capacity and increased the plateau pressure due to the formation of a Ti2Ni secondary phase, and to the incorporation of Mn into the BCC matrix phase. Increasing the V content was found to be an effective way of stabilizing the BCC phase, and thereby increasing the protium storage capacity. For Ti-V-Cr-Ni alloys, the slope of the plateau region was also improved by increasing the V content. In addition, the Mn-added alloy after annealing at 1573 K exhibited an almost uniform BCC solid solution and a storage capacity as high as 2.6mass%; however, the Ni-added alloy still contained the Ti2Ni phase. The addition of Mn was found to be an effective way of decreasing the slope of the plateau region.
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