The homogeneous plastic flow of fully amorphous and partially crystallized Zr(41.2)Ti(13.8)Cu(12.5)Ni(10)Be(22.5) bulk metallic glass (Vitl) has been investigated by compression tests at high temperatures in supercool...The homogeneous plastic flow of fully amorphous and partially crystallized Zr(41.2)Ti(13.8)Cu(12.5)Ni(10)Be(22.5) bulk metallic glass (Vitl) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory. Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystaltized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amorphous alloy. Thus, it is proposed that the flow behavior of the nanocrystalline/amorphous composite at 646 K is mainly controlled by the viscous flow of the remaining supercooled liquid.展开更多
In order to examine the effects of structure stability on the degradation behaviors of multiphase La0.7Mg0.3Ni3 alloy,changes of the crystal structure and hydrogen storage properties after gas-solid cycling were inves...In order to examine the effects of structure stability on the degradation behaviors of multiphase La0.7Mg0.3Ni3 alloy,changes of the crystal structure and hydrogen storage properties after gas-solid cycling were investigated in detail.The structural analysis identifies that（La,Mg）Ni3（PuNi3-type） phase transforms to amorphous,i.e.,hydrogen-induced amorphization（HIA） occurs whereas LaNi5（CaCu5-type）,（La,Mg）2Ni7（Ce2Ni7-type）,and（La,Mg）5Ni19（Pr5Co19-type） phases still keep crystalline upon hydriding/dehydriding cycling.Partial amorphization remarkably affects both the gas-solid and electrochemical storage performances.The plateau of PCT curves becomes narrow and steep with cycling.Moreover,the maximum electrochemical capacity decreases notably after gas-solid hydrogenation repeats.The electrochemical capacity reduction could be ascribed to both drop of the maximum storage capacity and the slope of plateau induced by partial amorphization.For direct electrochemical cycling,it is suggested that the capacity decay is mainly attributed to HIA in the initial stage.展开更多
文摘The homogeneous plastic flow of fully amorphous and partially crystallized Zr(41.2)Ti(13.8)Cu(12.5)Ni(10)Be(22.5) bulk metallic glass (Vitl) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory. Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystaltized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amorphous alloy. Thus, it is proposed that the flow behavior of the nanocrystalline/amorphous composite at 646 K is mainly controlled by the viscous flow of the remaining supercooled liquid.
基金financially supported by the National Natural Science Foundation of China(Nos.51161015 and 51371094)the Application Technology Research and Development Foundation of Inner Mongolia(No.20111401)the Innovation Foundation of Inner Mongolia University of Science and Technology(No.2012NCL024)
文摘In order to examine the effects of structure stability on the degradation behaviors of multiphase La0.7Mg0.3Ni3 alloy,changes of the crystal structure and hydrogen storage properties after gas-solid cycling were investigated in detail.The structural analysis identifies that（La,Mg）Ni3（PuNi3-type） phase transforms to amorphous,i.e.,hydrogen-induced amorphization（HIA） occurs whereas LaNi5（CaCu5-type）,（La,Mg）2Ni7（Ce2Ni7-type）,and（La,Mg）5Ni19（Pr5Co19-type） phases still keep crystalline upon hydriding/dehydriding cycling.Partial amorphization remarkably affects both the gas-solid and electrochemical storage performances.The plateau of PCT curves becomes narrow and steep with cycling.Moreover,the maximum electrochemical capacity decreases notably after gas-solid hydrogenation repeats.The electrochemical capacity reduction could be ascribed to both drop of the maximum storage capacity and the slope of plateau induced by partial amorphization.For direct electrochemical cycling,it is suggested that the capacity decay is mainly attributed to HIA in the initial stage.
