Influence of rare earth elements on aluminium metal matrix composites: A review

In view of the unique characteristics and diverse applications of composite materials; researchers across the world are focusing on the development of a variety of Metal-Matrix Composites (MMCs), particularly in the domain of Aluminium-based MMCs (AMMCs). The present research paper focuses on the study of the influence of rare earth elements (REEs) and rare earth oxides (REOs) on the Tensile Strength, Hardness, and Microstructure of AMMCs. Apart from the fraction, shape, and size of the reinforced particle, the fabrication methods also play a crucial role in the microstructure and performance of the composite. Stir casting and Powder metallurgy are the methods that are commonly used over the globe for processing of AMMCs due to their availability, simplicity, and low-cost production. During stir casting, the nature and characteristics of AMMCs largely depend upon geometrical parameters like impeller design and process parameters such as stirring speed, stirring time, and stirring temperature. However, in Powder Metallurgy, process parameters such as blending time, sintering temperature, and compact pressure have a significant effect on the performance of AMMCs. From previous studies, it has been observed that the tensile strength of AMMCs having REEs and REOs as reinforcement varies in the range of 26 MPa to 562 MPa, and the elongation during tensile tests enhanced up to 33.33 %. It is also observed that the hardness value of AMMCs with REEs and REOs particulates occurred in the range of 46 VHN to 260 VHN. From the survey of microscopic images, it is concluded that grain refinement and the formation of the useful compounds between aluminum matrix and rare earth particles helped in the enhancement of the mechanical properties of the AMMCs. It is also observed that the excessive use of reinforcement particles results in agglomeration that leads to a reduction in mechanical properties.