Abstract

Herein, high strength Al-Zn(-Mg) alloy designated as AA7068 based composites containing twin unlike dispersoids of ZrO_2p and Gr_p were synthesized through an enhanced stir-squeeze caster. The density of the casted materials accompanying porosity was investigated through the liquid displacement technique following the Archimedes principle. Mechanical behavior, such as hardness, impact toughness, tensile strength, and ductility was examined under the as-casted, artificially aged (T6), and retrogressed and reaged (RRA) conditions. Microstructural analysis and determination of intermetallic compounds were carried out using FESEM-EDX and XRD techniques. The fractured surface under tensile loading was also examined through FESEM to recognize the governing mode of failure. Hardness, 0.2% proof stress, and UTS of the composite containing 4 wt.% of ZrO_2p were improved over monolithic alloy up to 29.8, 68.2, and 37.5% at the as-casted condition and 43.5, 86.3, and 85% at artificially aged condition, respectively. However, the addition of Gr_p decreased the properties mentioned above. On the contrary, the addition of both the particulates of ZrO₂ and Gr (added separately or concurrently) decreased the ductility and impact strength irrespective of the material condition. FESE micrographs reveal the uniform distribution of dispersoids in the matrix phase. Furthermore, fractography depicts that the monolithic AA7068 matrix fractured in a ductile manner, while interfacial decohesion and particle cracking were the prime causes of failure in the composites.

摘要

在此，高强度 Al-Zn(-Mg) 合金被命名为 AA7068 基复合材料，包含 ZrO _2p和 Gr _{p的孪晶不同分散体}通过增强的搅拌挤压铸造机合成。根据阿基米德原理，通过液体置换技术研究了伴随孔隙率的铸造材料的密度。在铸态、人工时效 (T6) 和后退和再时效 (RRA) 条件下检查机械性能，例如硬度、冲击韧性、拉伸强度和延展性。使用 FESEM-EDX 和 XRD 技术进行金属间化合物的微观结构分析和测定。还通过 FESEM 检查了拉伸载荷下的断裂表面，以识别失效的控制模式。_{含有 4 wt.% ZrO 2p}的复合材料的硬度、0.2% 屈服强度和 UTS在铸态条件下比整体合金提高了 29.8%、68.2% 和 37.5%，在人工时效条件下分别提高了 43.5%、86.3% 和 85%。然而，Gr _p的添加降低了上述性能。相反，ZrO ₂和Gr颗粒的添加（单独或同时添加）降低了延展性和冲击强度，而与材料条件无关。FESE 显微照片揭示了分散体在基质相中的均匀分布。此外，断口分析表明，整体 AA7068 基体以延展方式断裂，而界面脱聚和颗粒开裂是复合材料失效的主要原因。