In this study, a NbB₂/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique, followed by hard-plate rolling and short-term annealing. The effect of NbB₂ particles on the microstructural evolution of the AZ91 alloy was investigated. The presence of NbB₂ was shown to have a grain-refining effect on the AZ91 alloy and promoted dynamic recrystallization (DRX) and precipitation of fine Mg₁₇Al₁₂ phases via particle-stimulated nucleation (PSN). Tensile testing revealed substantial enhancements in the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of the as-rolled AZ91 alloy, with values of 379 MPa, 292 MPa, and 14.7 %, respectively, owing to the incorporation of NbB₂ particles. Annealing led to further enhancements in EL with slight reductions in UTS and YS (360 MPa, 252 MPa, and 16.8 %, respectively). Owing to grain refinement and the PSN effect of the NbB₂ particles, a significant number of geometrically necessary dislocations (GNDs) were induced in the matrix during the rolling process, which reduces the nucleation barrier and increases the number of nucleation sites for the recrystallized grains and Mg₁₇Al₁₂ precipitates. Meanwhile, many residual dislocations and fine Mg₁₇Al₁₂ precipitates in the as-rolled alloys were annihilated during annealing, resulting in slight grain growth and coarsening. The strengthening mechanism of the NbB₂/AZ91 composite are mainly associated with grain-refinement strengthening, particle-induced dislocation strengthening, strengthening resulting from mismatching coefficients of thermal expansion (CTE), and hetero-deformation-induced (HDI) strengthening. Textural weakening, increased activation of non-basal slip systems, more-uniform strain patterns resulting from NbB₂ particles, and precipitation are mainly responsible for enhancing ductility.

中文翻译：

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硬质板轧制退火处理对NbB2颗粒增强AZ91复合材料组织和力学性能的影响


在本研究中，使用样品铸造技术制造了表现出理想机械性能的 NbB₂/AZ91 复合材料，然后进行硬板轧制和短期退火。研究了 NbB₂ 颗粒对 AZ91 合金微观组织演变的影响。NbB₂ 的存在被证明对 AZ91 合金具有晶粒细化作用，并通过颗粒刺激成核 （PSN） 促进动态再结晶 （DRX） 和细 Mg₁₇Al₁₂ 相的沉淀。拉伸测试显示，由于掺入 NbB₂ 颗粒，轧态 AZ91 合金的极限拉伸强度 （UTS）、屈服强度 （YS） 和伸长率 （EL） 显着提高，值分别为 379 MPa、292 MPa 和 14.7 %。退火导致 EL 进一步增强，UTS 和 YS 略有降低（分别为 360 MPa、252 MPa 和 16.8 %）。由于 NbB₂ 颗粒的晶粒细化和 PSN 效应，在轧制过程中在基体中诱导了大量几何必要位错 （GND），这减少了成核屏障并增加了再结晶晶粒和 Mg₁₇Al₁₂ 沉淀物的成核位点数量。同时，轧态合金中的许多残余位错和细小的 Mg₁₇Al₁₂ 析出物在退火过程中被湮灭，导致晶粒轻微生长和粗化。 NbB₂/AZ91复合材料的强化机制主要与晶粒细化强化、颗粒诱导位错强化、热膨胀系数不匹配（CTE）引起的强化和异质变形诱导（HDI）强化有关。织构弱化、非基底滑移系统活化增加、NbB₂ 颗粒产生的更均匀的应变模式以及沉淀是增强延展性的主要原因。