Modification of BCC phase and the enhanced reversible hydrogen storage properties of Ti-V-Fe-Mn alloys with varied V/Fe ratios

Ti-V-based alloys are proved of huge potential in storing hydrogen,but the incomplete reversible hydrogen storage capacity caused by overstability of V hydride has limited the large-scale application.In this study,Ti_(32)V_(40+x)Fe_(23-x)Mn_(5)(x=0,4,8,12,at.%)alloys were designed,and the effects of V/Fe ratio on phase constitution and hydrogen storage properties were investigated.The main phase of the alloys is body-centered cubic(BCC)phase,and the lattice constants of the BCC phase decrease with the decrease of V/Fe ratio.Moreover,C14 Laves phase exists in alloys with a Fe content of 19at.%to 23at.%.For hydrogenation,the C14 Laves phase can accelerate the hydrogen absorption rate,but the hydrogen absorption capacity is reduced.With the decrease of V/Fe ratio,the hydride gradually destabilizes.Owing to its large lattice constant and high hydrogen absorption phase content,the Ti_(32)V_(52)Fe_(11)Mn_(5)alloy shows the most enhanced hydrogen storage properties with hydrogenation and dehydrogenation capacities of 3.588wt.%at 298 K and 1.688wt.%at 343 K,respectively.The hydrogen absorption capacity of this alloy can be reserved to 3.574wt.%after 20 cycles of hydrogen absorption and desorption.

Effect of V and Sn on microstructure and mechanical properties of gray cast iron

The cylinder liner is one of the important parts of a diesel engine.Gray cast iron is the main material for manufacturing cylinder liners due to its good casting performance,convenient processing performance,good wear resistance and low cost.In the present work,the effects of vanadium(V)and tin(Sn)on the microstructure and properties of gray cast iron were studied.Results show that increasing the contents of V and Sn can not only refine the graphite,but also reduce the pearlite lamellar space.The graphite size and lamellar spacing of pearlite are firstly reduced and then increased.Pearlite quantity reaches over 98%after adding V and Sn.Adding V and Sn can promote the precipitation and solid solution strengthening of gray cast iron,so as to improve the mechanical properties.The Brinell hardness reaches the peak of 424 HB at the contents of 0.21wt.%V and 0.06wt.%Sn,and the sample containing 0.11wt.%V and 0.08wt.%Sn shows the highest compressive strength and tensile strength of 1,699 MPa and 515 MPa,respectively.The main strengthening mechanism comes from the solid solution strengthening and fine grain strengthening of V and Sn.