利用热力学计算软件JMatPro和相应的镍基高温合金数据库, 研究了U720Li合金以及在此基础上研发的新型Ni-Co基高温合金的化学成分对平衡相的析出行为、加工性能和γ/γ'晶格错配度的影响. 结果表明: Ti/Al值(原子比)的增加提高了合金中γ/γ'相的晶格错配度, γ'析出相的含量随Ti+Al含量(原子分数)的增加而增加. 因此, 增加Ti/Al值和Ti+Al含量能提高合金的高温强度. Co含量的升高可以拓宽合金的加工窗口, 改善合金的加工能力, 并且还可以增加合金γ/γ'相的晶格错配度, 提高合金错配强化的效果. 同时, Ti/Al值的增加促进合金中η相析出, 而Co含量的增加具有抑制η相的效果. 因此, 在 Co含量较高的Ni-Co基高温合金中, 适当提高Ti含量, 增加Ti/Al值对提高合金高温强度有利.
Thermodynamic properties of the traditional U720Li alloy and the new Ni-Co base superalloy have been studied using JMatPro and the latest relevant database for Ni base superalloys. The effects of chemical composition on the equilibrium precipitation phases, process-ability and γ/γ' mismatch have been analyzed. It is found that the γ/γ' mismatch increases with the increase of Ti/Al (atomic ratio). The volume fraction of γ' is proportional to the Ti+Al contents (atomic fraction). Therefore, by increasing the Ti/Al ratio and Ti+Al content, the yield strength of alloys can be improved. On the other hand, the γ' solvus temperature decreases by Co additions. As a result, the range of processing temperature is extended. The γ/γ' mismatch also increases with Co additions, which adds additional strengthening to the alloy. Moreover, high Ti/Al ratio or low Co content promotes the precipitation of η phase. Thus, Ni-Co base superalloys with high Ti+Al content, Ti/Al ratio and Co content bear an improved strength, phase stabilities and process-ability.
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