During thermo-mechanical processing of a Ni-Mo alloy, three hot-rolled slabs at 1250 °C have been stacked on top of each other during air-cooling. Upon reaching ambient temperature, the middle slab is found to develop a mid-length transverse crack running through the entire thickness. However, no cracks have been detected in the other slabs. It is shown that the middle slab has been embrittled by ordering to Ni₄Mo due to comparative slower cooling rate. An investigation of the ordering behavior of stoichiometric Ni₄Mo alloy has shown that ordering occurs homogeneously during the earlier stages of thermal aging at elevated temperatures which results in nanosized structure of ordered Ni₄Mo domains capable of deforming by twinning and characterized by high strength and high ductility However, due to self-induced recrystallization by grain boundary migration during extended thermal exposure, the homogeneous nanosized structure is replaced by coarse platelets in the matrix and coarse lamellar structure at grain boundaries resulting in severe embrittlement. It is demonstrated that this problem can be combated by doping with either boron or yttrium which tend to segregate at grain boundaries and reduce their tendency toward migration and therefore self-induced recrystallization. Therefore, the desirable nanosized morphology of Ni₄Mo is restored in the matrix phase and the lamellar grain boundary morphology is replaced by nanosized layers of Ni-Mo solid-solutions with compositions not susceptible to Ni₄Mo ordering. As a result, the doped alloys become able to maintain high strength and high ductility after extended thermal aging at elevated temperatures.

在 Ni-Mo 合金的热机械加工过程中，三个 1250 °C 的热轧板坯在空冷过程中相互堆叠。达到环境温度后，发现中间板会产生贯穿整个厚度的中等长度横向裂纹。然而，在其他板坯中没有检测到裂纹。结果表明，由于相对较慢的冷却速度，中间板坯已通过向 Ni ₄ Mo订购而发生脆化。对化学计量的 Ni ₄ Mo 合金有序行为的研究表明，在高温热老化的早期阶段，有序发生均匀，这导致有序的 Ni ₄纳米结构Mo 域能够通过孪晶变形并具有高强度和高延展性的特点 然而，由于在长时间的热暴露过程中通过晶界迁移引起的自诱导再结晶，均匀的纳米结构被基体中的粗片和晶粒中的粗片层结构所取代边界导致严重脆化。事实证明，可以通过掺杂硼或钇来解决这个问题，这些硼或钇倾向于在晶界处偏析并降低它们的迁移趋势，从而降低自诱导再结晶的趋势。因此，理想的 Ni ₄纳米级形貌Mo 在基体相中恢复，层状晶界形态被 Ni-Mo 固溶体的纳米层取代，其组成对 Ni ₄ Mo 排序不敏感。因此，掺杂合金在高温下长时间热老化后能够保持高强度和高延展性。