Measurements of hydrogen absorption desorption behavior of Nb Al alloys, Nb ss (Nb solid sloution), Nb ss +Nb 3Al, Nb 3Al, Nb 3Al+Nb 2Al, were carried out under hydrogen pressure from 0 to 3.4 MPa at 353 and 357 K, along with mircostructural observation and X ray diffraction analysis. It was found that single phase alloys of Nb ss and Nb 3Al are not pulverized regardless of a considerable amount of hydrogen absorption, while two phase alloys of Nb ss +Nb 3Al and Nb 3Al+Nb 2Al are readily pulverized. X ray diffraction analysis indicated that no hydride with crystal structure different from constituent phases is formed by hydrogen absorption, but lattice parameters of Nb ss and Nb 3Al are increased. Pulverization of Nb Cr alloys was investigated under a hydrogen atmosphere of 0.1 MPa in an arc melting chamber without exposure to air after arc melting. Similarly, hydrogen pulverization occurs only in two phase alloys consisting of Nb ss and NbCr 2. Based on the measured lattice parameters of Nb ss and Nb 3Al(NbCr 2) in the hydrogenated two phase alloys and the microstructural observations, a mechanism for hydrogen pulverization is discussed.
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