Journal of Advances in Physics Vol 17 (2020) ISSN: 2347-3487 https://rajpub.com/index.php/jap 79 Microstructural Characterization and Mechanical Properties of Rapidly Solidified Al-Si Systems by Chill Block Melt-Spinning Technique. DOI: https://doi.org/10.24297/jap.v17i.8607 Rizk Mostafa Shalaby 1 , Amal Abdallah 1 , Mustafa Kamal 1 1 Metal Physics Laboratory, Physics Department, Faculty of Science, Mansoura University, Mansoura, Egypt. amal.elsherif11@gmail.com, rizk2002@mans.edu.eg Abstract AlـSi alloys with compositions (0, 0.1, 0.5, 0.9, and 1.3 wt.% Si) were manufactured by chill block melt spinning method. The resulting ribbons samples have been characterized by x ـray diffraction (XRD) and scanning electron microscope (SEM). Detailed analysis of (XRD) shows that presence of f.c.c Al solid solution and Si particles embedded within the aluminum grains. The microstructural examination resulted that the microstructure of the melt-spun ribbons is finer and uniformly distributed. Rapid solidification technology led to increase the solubility of Si in αـAl as confirmed by XRD. Micro hardness measurements were also carried out by Vickers micro ـhardness tester at applied load 25gm forced and different dwell time. It is concluded that the Vickers hardness values are sensitive to applied load and indentation time. It is also found that the highest values of Hv is sensitive to presence of Si as columnar shape with fine-grained of Al by high cooling rate. Keywords: AlـSi Alloys, Structure, Microstructure, Mechanical Properties, Micro Hardness Test, Electrical Resistivity, Micro-Creep 1. Introductions Aluminum-Silicon alloys are used on a large scale in different fields of industry. These alloys are multipurpose matter, it comprises a large present of the total cast parts of aluminum reach to 85% to 90% produced for aerospace and automotive field industry[1,2]. Aluminumــsilicon alloys where Al is a base element in alloying, include a type of material, which enhance the most important part of all shaped castings that used in manufacture, these alloys have a lot of applications in the aerospace and automotive industries [3]. This is because of the effect of silicon that affect effectively in the enhancement of casting features, in addition to other physical properties, like corrosion resistance and mechanical properties [4]. These alloys also used heavily in buildings fields and constructions, packaging marine, containers, aviation, aerospace, and electrical industries due to their features as corrosion resistance and lightweight, in most environments. Mechanical properties are controlled by the Manipulation in the microstructure through adding small alloying elements. During solidification, microstructure evolution of hypoeutectic Al ــSi alloys is in two periods: primary dendrite AL phase formation (αـــmatrix), and subsequently eutectic transformation (eutectic Si particles in αـــmatrix). Depending on the distribution and the shape of the silicon particles ,the mechanical properties of Al-Si alloys are determined [5]. Nowadays Aluminum alloys or other lightweight alloys have a lot of application in manufacturing industries and automotive industries, as they augment the engine efficiency because they have the ability to reduce weight along with it can retain the strength that is desired to resist the same strength of cast iron. These lightweight alloys also decrease the consumption of shields the surroundings and fuel, so steel parts and cast iron can replaced by it successfully[6–8]. The development of aluminum base alloys which have important features such as low weight, high stiffness and high tensile strength have extensively been required because of its expectation of the improvement of structural efficiency to reduce fuel consumption and transportation vehicle. Although there are a lot of materials are used in rapid solidification technique, AlـــSi alloys are very favored because of Si has a very limited solid solubility in Al in conventional techniques[9,10]. Based on Si concentration in weight percent (wt.%), the system of AlـــSi alloy located in three stages: hypoeutectic area (<12% Si), eutectic area (12ــ13% Si) and hypereutectic as seen in the equilibrium phase diagram (Fig. 1)[11]. The aluminum density is 2.7, besides that, the low density of Silicon (2.34 g cm -3 ) is a very important property, this advantage is used to