W掺杂对Nb固溶体抗氢脆及透氢性能的改性研究

Study on Modification of Hydrogen Embrittlement and Hydrogen Permeability of Nb Solid Solution by W Doping

摘要:

元素掺杂是消除Nb金属氢脆问题的有效方法。本文制备了W掺杂的Nb100-xWx (x=2,5,8,10,16)合金，采用XRD、SEM、Sieverts 气体吸附技术、电化学方法和三点弯曲试验研究了掺杂量对合金结构、氢化物形成焓、氢扩散系数和抗氢脆机械力学性能的影响。研究证实，熔炼制备Nb100-xWx为Nb-bcc结构的固溶体合金，W掺杂引起晶体结构畸变收缩，其畸变行为随掺杂量增大更为明显。Nb基固溶体在匀晶转变时存在非平衡转变，形成富W和贫W区相间分散的枝状结晶形貌。随W掺杂量增大，其枝状结构趋于更加细化和致密、分界明显。W掺杂引起合金的氢化物形成焓增大、有利于H原子的释放，Nb84W16合金样品具有最大的氢扩散系数（1.66×10-9 cm2·s-1），约是Nb98W2合金的1.8倍。W掺杂提高Nb100-xWx固溶体合金的抗氢脆性能，Nb84W16合金膜有最大的临界载荷值（78.4N）和最大位移量（0.83mm），分别是Nb98W2合金膜的1.9倍和1.8倍，力学性能的改善与其枝状结晶结构有关。

Abstract:

Doping is an effective way to eliminate the problem of hydrogen brittleness of Nb metal. Phase structure, hydride formation enthalpy, hydrogen diffusion coefficient (DH) and mechanical properties of W-doped Nb100-xWx (x=2,5,8,10,16) alloys have been investigated by XRD, SEM, PCT analysis, electrochemical method and three-point bending test respectively. The results indicated that melting-prepared Nb100-xWx samples are Nb-based solid solutions with bcc structure. W-doping will induce the lattice distortion and shrink, the distortion behavior is more obvious with the increase of W-doping content. Non-equilibrium transformation microstructure is observed in these Nb100-xWx samples, which presents dendritic morphology with W-poor region dispersed in W-rich matrix. Dense and refined dendritic morphology is observed obviously in Nb100-xWx (x=10, 16) samples. W-doping results in the increase of the value of hydride-formation enthalpy, and benefits H-release of corresponding hydride. Higher H-diffusion coefficient (DH=1.66×10-9 cm2·s-1) is obtained in Nb84W16 sample, which is about 1.8 times that of Nb98W2 sample. W-doping also improve the anti-hydrogen embrittlement capacity, Nb84W16 sample has the largest maximum load (78.4N) and maximum displacement (0.83mm), which is about 1.9 and 1.8 times that of Nb98W2 sample respectively, indicating that the improvement of mechanical properties is related to its microstructure.