Previous studies revealed that developing bi-modally structured α-Mo grains in the fine-grained Mo-12Si-8.5B-0.57 wt% La₂O₃ alloy could improve room-temperature fracture toughness without sacrificing strength dramatically. However, the toughness is expected to be enhanced further for engineering application of alloy. Here, the optimization of the bimodal α-Mo microstructure was achieved by annealing treatment at 1700–1800 °C. After annealing, the semi-continuous or isolated α-Mo colonies were transformed into the continuous α-Mo matrix meanwhile the volume fraction of α-Mo was improved slightly. Besides, the fine-grained and coarse-grained regions were coarsened concurrently and the distribution of them became more homogenous. The 1800 °C-annealed bimodal alloy exhibited an optimal microstructure consisting of dispersive Mo₃Si/Mo₅SiB₂ (~1.72–2.00 μm) particles distributed in a continuous bimodal fine-grained (~2.03 μm)/coarse-grained (~6.36 μm) α-Mo matrix. Also, this alloy presented a significantly improved fracture toughness (13.41 MPa·m^1/2) and high compression strength (2682 MPa) and hardness (841 HV) simultaneously. Toughening mainly originated from crack trapping in the coarsening bimodal α-Mo structure and forming intragranular micro-cracks in the coarsening α-Mo and intermetallic phases induced by La₂O₃. High compression strength was attributed to the coarseness of α-Mo phase improving the plastic deformation capacity of alloy.

先前的研究表明，在细粒Mo-12Si-8.5B-0.57 wt％La ₂ O _3中形成双峰结构的α-Mo晶粒合金可以提高室温断裂韧性而不会显着降低强度。但是，在合金的工程应用中，韧性有望进一步提高。在此，通过在1700–1800°C下进行退火处理，实现了双峰α-Mo微结构的优化。退火后，将半连续或分离的α-Mo菌落转化为连续的α-Mo基质，同时α-Mo的体积分数略有提高。此外，细粒度和粗粒度区域同时被粗化，并且它们的分布变得更加均匀。1800°C退火的双峰合金表现出由分散的Mo ₃ Si / Mo ₅ SiB ₂组成的最佳微观结构（〜1.72–2.00μm）颗粒分布在连续的双峰细颗粒（〜2.03μm）/粗颗粒（〜6.36μm）α-Mo基质中。而且，该合金同时具有显着改善的断裂韧性（13.41 MPa·m ^1/2）和高压缩强度（2682 MPa）和硬度（841 HV）。增韧主要源于粗化双峰α-Mo结构中的裂纹俘获，并在La ₂ O ₃引起的粗化α-Mo和金属间相中形成晶内微裂纹。高压缩强度归因于α-Mo相的粗度提高了合金的塑性变形能力。