In this research, microstructure and mechanical properties of stir rheocast AA2024/TiB2 metal matrix composite have been investigated. The working temperature was 640℃, which was the selected semisolid temperature that corresponds to 40% of the solid fraction. Two weight percentage, 4 wt%, and 6 wt% of the TiB2 reinforcements were added to the matrix. The field emission scanning electron microscope micrographs of the developed composites showed a uniform distribution of the particles in the case of the 2 wt% and 4 wt% of the reinforcements. However, the particles agglomerated as the weight percentages of the reinforcement increases to 6%. The optical microscope of the liquid cast sample showed the dendritic structure, whereas the rheocast samples showed a globular structure. The X-ray diffraction analysis confirmed the distribution of the reinforcements in the matrix and the formation of some intermetallic compounds. Mechanical properties significantly improved by the addition of the reinforcements in the matrix. An increase in tensile strength of 13.3%, 40%, 28%, and 5% was achieved for the unreinforced rheocast sample, 2 wt%, 4 wt%, and 6 wt% reinforced rheocast samples respectively, compared to the liquid cast sample. An increase in 20% of hardness was attained for the composite with 2 wt% TiB2 compared to the liquid cast sample. According to the fractography analysis, small dimples were observed on the fractured surface of the unreinforced rheocast sample, whereas small and large voids were dominant on the fractured surface of the 2 wt% composite, which shows the ductile fracture mode.

中文翻译：

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搅拌流变铸件 AA2024/TiB2 复合材料的显微组织表征及力学性能评价

本研究对搅拌流变铸造 AA2024/TiB2 金属基复合材料的微观结构和力学性能进行了研究。工作温度为640℃，这是选定的半固体温度，对应于40%的固体分数。将两个重量百分比、4 重量％和 6 重量％的 TiB2 增强材料添加到基体中。所开发复合材料的场发射扫描电子显微镜显微照片显示，在 2 wt% 和 4 wt% 增强材料的情况下，颗粒分布均匀。然而，随着增强材料的重量百分比增加到 6%，颗粒会聚集。液态浇铸样品的光学显微镜显示出树枝状结构，而流变浇铸样品显示出球状结构。X射线衍射分析证实了增强体在基体中的分布和一些金属间化合物的形成。通过在基体中添加增强材料，机械性能显着提高。与液体浇铸样品相比，未增强的流变浇铸样品、2wt%、4wt% 和 6wt% 的增强流变浇铸样品的拉伸强度分别提高了 13.3%、40%、28% 和 5%。与液态铸造样品相比，具有 2wt% TiB2 的复合材料的硬度增加了 20%。根据断口分析，在未增强流变铸件的断口表面观察到小凹坑，而在 2 wt% 复合材料的断口表面上以小和大的空隙为主，显示出韧性断裂模式。