The exceptional mechanical properties of polycrystalline nickel-based superalloys arise through various concurrent strengthening mechanisms. Whilst these mechanisms are generally understood, consensus has yet to be established on the precise contribution of each to the overall alloy strength. Furthermore, changes in alloy chemistry influence several different mechanisms, making the assessment of individual alloying elements complex. In this study, a series of model quinary Ni-based superalloys has been investigated to systematically study the effect of varying Mo content on the contributing strengthening mechanisms. Using microstructural data, the yield strength was modelled by summing the individual effects of solid solution in both the γ and γʹ phases, coherency, grain boundary and precipitation strengthening. The total predicted yield stress increased with Mo content despite the diminishing contribution of precipitation strengthening. It is shown that solid solution strengthening of the ordered γʹ precipitate phase is a key contributor to the overall strength, and that variations in composition between the tertiary and secondary γʹ lead to significant changes in mechanical properties that should be accounted for in models of alloy strength.

多晶镍基高温合金的优异机械性能是通过各种同时发生的强化机制产生的。尽管通常理解了这些机理，但尚未就每种对合金整体强度的精确贡献达成共识。此外，合金化学的变化会影响几种不同的机理，从而使对单个合金元素的评估变得复杂。在这项研究中，已经研究了一系列模型五元镍基高温合金，以系统地研究不同的钼含量对促进机制的影响。利用微观结构数据，通过总结固溶体在γ相和γʹ相中的各个作用，相干性，晶界和析出强化的影响，对屈服强度进行建模。尽管降水增加的作用减弱，但总的预测屈服应力随Mo含量的增加而增加。结果表明，有序γʹ析出相的固溶强化是整体强度的关键因素，第三和第二γʹ之间的成分变化会导致机械性能发生重大变化，这应在合金强度模型中加以考虑。