Nb-Ti-Co Quasiperitectic Alloy And Its Hydrogenation Behavior

Niobium（Nb）series alloys have developed rapidly in recent years due to their good high-temperature strength and outstanding low-temperature plasticity.Among them,Nb-Ti-Co ternary alloys have a wide range of applications as a new functional material in the field of hydrogen separation,electromagnetism and biomedicine,making them a research hotspot for scholars from various countries.The research on the solidification theory of niobium-based binary alloys has been relatively mature,but a relatively complete solidification theory system for multi-alloys has not yet been established,therefore,in-depth research on the solidification theory of multi-alloys will be one of the main directions of future solidification science.In addition,some scholars found in the study of hydrogen separation that Nb-Ti-Co ternary alloys undergo a quasiperitectic reaction during solidification,L+α→β+γ.From the reaction formula,it has the dual characteristics of both eutectic and package crystal reactions,and involves more complex phase change reactions,and people know little about its solidification characteristics,and its solidification mechanism is not yet clear.Therefore,it is of great theoretical and engineering significance to study the tissue evolution and solidification mechanism of the quasiperitectic alloy to promote the practical application of Nb-Ti-Co ternary alloys.On the basis of this,this paper will study the microstructure evolution and solidification mechanism by Bridgman the legal solidification technology,selecting the components near the eutectic point in the phase diagram,and combining with the application of Nb-Ti-Co ternary alloy in the field of hydrogen separation and corrosion resistance are explored.The main conclusions are as follows:（1）Excellent Nb₁₀Ti₆₁Co₂₉and other 4 component points for directional solidification experiment,clarify the evolution of solidification structure of Nb-Ti-Co quasiperitectic alloy,we combined with CALPHAD methods and make clear its solidification path:（a）L→BCC-（Nb,Ti）;（b）L→BCC-（Nb,Ti）+Ti Co,of binary eutectic reaction（c）L+Ti Co→BCC-（Nb,Ti）+Ti₂Co,of ternary and（d）L→BCC-（Nb,Ti）+Ti₂Co,of binary eutectic reactions.（2）Hydrogen content of Nb-Ti-Co as-cast and directional solidified alloys increases with the increase of hydrogen flow and holding time.However,the hydrogen content of the alloy has an upper limit value,and when the holding time and hydrogen flow rate are fixed,the hydrogen content will increase with the increase of temperature.And the hydrogen content of the directional solidified alloy is always larger than that of the as-cast alloy,and the hydrogen content and microhardness of the alloy increase with the increase of the Nb content in the alloy the increase of growth rate.（3）The corrosion resistance of eight Nb-Ti-Co alloys,including Nb₃₀Ti₃₅Co₃₅,was measured by electrochemical experiments,and the variation law between alloy composition and organization（or phase structure）was elucidated;the corrosion resistance mechanism of Nb-Ti-Co alloys was proposed,and the fundamental reason for the relatively weak corrosion resistance of alloys with high Nb content was revealed for the first time,and the intrinsic relationship between alloy composition-microstructure and corrosion resistance was constructed.The intrinsic relationship between alloy composition-microstructure-corrosion resistance was constructed.