Hydrogen alloying

Attack on softer boiling corrosion pitting. handling hydrogen alloy steel with immediately above hardness under C 22... 

Certain peculiarity was characteristic of each alloy studied. For example, any hydrogen content embrittled the non-alloyed titanium at room temperature. Other behavior was observed on the Ti-6A1-4.5V alloy at room temperature and low strain rates. The ultimate compressive strain of this alloy without hydrogen was about 8.5% at = 10 s while hydrogen alloying to r = 0.27 increased this value to about 20% and to 10 to 14% at other x. 

This effect was estimated from the experimental comparison of the stress-strain properties in three sample series which were brought to different phase contents by means of heat treatment. All samples were hydrogen-alloyed to a = 0.35 at T = 1053 K, then furnace cooled. Before straining, samples of the first series were maintained at the test temperature for 0.5 h. Series 2 samples were heated to the j9-phase, T = 1163 K, for 15 min, then cooled to the test temperature and treated like series 1 samples. The phase content in the third series was equilibrated by heating to 1163 K and slow cooling to 903 K before the test temperature was fixed. 

Fig. 10 shows that the flow stress of the hydrogen-alloyed compacts is essentially less than that of the outgassed ones at all test temperatuics. The flow stress relation between the hydrogen-alloyed and outgassed compacts depended on the strain. At equal strains at test temperatures, this ratio could achieve 2 or more. Thus, the effect of hydrogen on the properties of compacted powders is much similar to that observed on bulk titanium. 

The basic alloy at atmospheric pressure and T = 20°C demonstrated the per cent elongation <5 = 31% and the per cent reduction ip = 65% while plastic properties of the hydrogenated alloy were close to zero. But an opposite relation was observed in tensile tests under a pressure of 6.5 kbar. The plastic properties of the hydrogenated alloy increased to <5 = 33% and /> = 83% at P = 6.5 kbar and T = 20°C while those of the basic alloy changed only slightly (Fig. 11). 

Hydrogen alloying increases ductility of titanium alloys by 10 to 45 times at moderate temperatures of 400 to 750 C. 

Hydrogen alloying decreases flow stress by 2 to 3 at optimum. 

Preliminary pre-strain thermal treatment of hydrogenated alloys increases content of the metastable phases and thus markedly increases the alloy ductility. 

O.N. Senkov, E.V. Konopleva, and E.G. Ponyatovsky, The effect of initial phase content and structure on workability of a hydrogen-alloyed titanium alloy, Fiz. Met. Metallovedeniye, 77 142 (1994). 

In a variant of the second method described earlier the premixed metallic powders (or pulverized ingots) are milled under hydrogen atmosphere to directly form an intermetallic hydride. It can be also viewed as hydrogen alloying of metal powders and powder mixtures in hydrogen alloying mills. This method is called a reactive mechanical alloying (RMA) or mechanochemical synthesis (MCS). 

Z.S. Wronski, R.A. Vatin, Ch. Chiu, T. Czujko, Mechanosynthesis of nanocrystaUine MgB ceramic powders in hydrogen alloying mills via amorphous hydride intermediate, Adv. Sci. Technol. 45 (2006) 309-314. 

Z. Wronski, R.A. Varin, C. Chiu, T. Czujko, A. Calka, Mechanochemical synthesis of nanostructured chemical hydrides in hydrogen alloying mills , J. Alloys Compd. 434-435 (2007) 743-746. 

Fukai Y, Kazama S. NMR studies of anomalous diffusion of hydrogen and phase transition in vanadium-hydrogen alloys . Acta Metall., (1977), 25, 59-70. 

Abstract. The interaction of hydrogen with spherical particles of an alloy such as BT5-1 containing 92.05 mass% of Ti, 4.52mass% of A1 and 3.43 mass% of Sn with diameters of particles of 0.1, 0.4, 0.6 and 0.8 mm was investigated at temperatures of 773-973 K and pressure of 1-6 MPa. It was shown that the alloy has the lower absorbed capacity on hydrogen in comparison with titanium and thermal stability of the hydrogenated alloys is lower than a stability of titanium dihydride. 

The mixtures of hydrogenated alloys Mg-Mm(La)-Ni and La(Mm)Ni5 were mechanochemically treated to prepare hydrogen storage composites with various content ratios. The performed investigations demonstrate the homogeneity of the composites, the absence of new phases and the composites having particle sizes of 10-80 pm. 

In 1981 an efficiency of 7.5% was obtained for a p-i-n structure (3.3 mm2) in which the p layer was a boron-doped silicon-carbon-hydrogen alloy (a-Si C H) (Tawada et al., 1981). A further improvement in conversion efficiency to 8.5% was obtained in 1982 with a stacked junction structure (9 mm2) that utilized an amorphous silicon-germanium-hydrogen alloy (a-Si Ge H) in the back junction of three stacked p-i-n junctions (Nakamura et al., 1982). More recently, an efficiency of 10.1% has been achieved in a p-i-n structure (1.2 cm2) utilizing p-type a-Si C H as a window layer (Catalano et al., 1982). 

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