J75抗氢合金中B的作用机制研究

MECHANISM OF B IN HYDROGEN-RESISTANCE J75 ALLOY

采用OM,SEM,TEM,EPMA和二次离子质谱(SIMS)等手段,研究了B对J75抗氢合金晶界h相析出的抑制作用机制,采用饱和热充氢、三维原子探针(3DAP)技术和氢渗透实验方法,研究了B对合金抗氢性能的影响机制.结果表明,不含B合金中存在Ti的晶界偏聚,导致晶界h相在时效过程中析出;含B合金中,由于B抑制了Ti的晶界偏聚,使h相难以形核长大,从而抑制了晶界h相的析出.B和H原子存在位置竞争关系,B降低合金的氢扩散系数,阻碍H原子的扩散和迁移,减少晶界偏聚H原子数量,抑制氢致裂纹形成.

With the development of hydrogen economy, the demand of structural materials with high strength suitable for service in hydrogen or hydrogen-bearing environments such as storage of hydrogen gas was incremental. An optional structural materials is J75 alloy, which is mainly strengthened by an ordered fcc γ′phase, Ni3（Al, Ti）, coherent with the austenite matrix. Investigation on J75 alloy indicated that the commercial alloy free of B would lose about half its ductility when charged with hydrogen, accompanied by a change of fracture mode from ductile rupture to brittle-appearing intergranular fracture. Otherwise, an improvement in ductility and hydrogen resistant performance was observed in the J75 alloy with trace B, however, its role in the alloy is unclear. So, in present work, mechanism of B in the J75 hydrogen-resistant alloy was investigated by means of OM, SEM, TEM, EPMA, 3DAP, SIMS, hydrogen penetration, thermal hydrogen charging experiments and tensile tests. It was found that a lot of Ti segregated at grain boundaries （GBs） in the alloy free of B, resulted in abundant precipitation of cellular η phases. However, the cellular η phase was not observed in the alloy with B, and it could be attributed to the segregation of B atoms at GBs and inhibited the segregation of Ti. A lower hydrogen diffusion coefficient was observed in the alloy with B than that in the alloy free of B by hydrogen permeation, indicating that diffusion velocity of H atoms in the alloy had been decreased by the addition of B. Moreover, segregation of B at GBs could not only inhibit the precipitation of η phases but also decrease the number of H atoms there, which would improve the hydrogen-resistant performance of the alloy.