Alrasheedi Nashmi H, Ataya Sabbah, El-Sayed Seleman Mohamed M, Ahmed Mohamed M Z
Department of Mechanical Engineering, College of Engineering, Imam Mohammad Ibn Saud Islamic University, Riyadh 11432, Saudi Arabia.
Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez University, Suez 43512, Egypt.
Materials (Basel). 2023 Jul 2;16(13):4785. doi: 10.3390/ma16134785.
Magnesium alloys are still attractive materials for applications that necessitate light weight due to their low density, moderate strength, and good corrosion resistance. AZ91 is one of the widely applied magnesium alloys due to its very good castability and strength. However, one of the drawbacks of magnesium alloys is the low elastic modulus. So, reinforcing AZ91 with carbon short fibers with the aim of further increasing the strength and improving the elastic modulus is investigated in this study. Squeeze cast AZ91-23 vol.% carbon short carbon (AZ91-C) and the unreinforced AZ91 are deeply examined by tensile testing at different temperatures (20, 100, 150, 200, 250, and 300 °C). Tensile stress-strain curves are measured and the tensile parameters (yield stress, ultimate tensile strength and strain) are defined and presented against the test temperature. Yield stress of AZ91 at 20 °C (109 MPa) is doubled (226 MPa) in the reinforced AZ91-C. Yield stress is found to slightly decrease with increasing the test temperature. Ultimate tensile strength of AZ91 at 20 °C (198 MPa) is increased (262 MPa) in the reinforced AZ91-C. The improvement of the ultimate tensile strength due to reinforcing increases with increasing the test temperature. Flow curves are determined and described by a modified Mecking-Kocks relationship and the flow parameters are determined and described as a function of the test temperature. Microstructure investigation was undertaken of the fractured tensile specimens at the grain boundaries rich in eutectic structure formed at the grain boundaries. Mixed brittle/ductile fracture mode is detected on the fracture surface of unreinforced AZ91, while the SEM investigations show matrix/carbon fiber detachment and fiber fracture as main fracture modes.
镁合金因其低密度、中等强度和良好的耐腐蚀性，仍是需要轻质材料的应用领域的有吸引力的材料。AZ91是应用广泛的镁合金之一，因其具有非常好的铸造性能和强度。然而，镁合金的缺点之一是弹性模量低。因此，本研究旨在通过用短碳纤维增强AZ91，进一步提高其强度并改善弹性模量。通过在不同温度（20、100、150、200、250和300℃）下进行拉伸试验，对挤压铸造的AZ91-23体积%短碳纤维（AZ91-C）和未增强的AZ91进行了深入研究。测量了拉伸应力-应变曲线，并定义并给出了拉伸参数（屈服应力、极限抗拉强度和应变）与试验温度的关系。在增强的AZ91-C中，AZ91在20℃时的屈服应力（109MPa）翻倍（226MPa）。发现屈服应力随试验温度升高略有降低。在增强的AZ91-C中，AZ91在20℃时的极限抗拉强度（198MPa）有所提高（262MPa）。由于增强导致的极限抗拉强度的提高随着试验温度的升高而增加。通过修正的Mecking-Kocks关系确定并描述了流动曲线，并确定并描述了流动参数与试验温度的函数关系。对拉伸断裂试样在富含晶界共晶组织的晶界处进行了微观结构研究。在未增强的AZ91的断口表面检测到脆性/韧性混合断裂模式，而扫描电子显微镜研究表明基体/碳纤维分离和纤维断裂是主要断裂模式。
