Search

• Al-7075 was reinforced by different contents of Fe-based metallic glass particles. • The composites were prepared by spark plasma sintering and hot extrusion. • The composites possess higher mechanical properties than unreinforced Al-7075. • The composites are reinforced mainly by thermal mismatch and grain refinement. Metallic glass (MG) reinforced aluminum matrix composites (AMCs) have attracted the interest of many researchers in the past few years. In this study, Fe 50 Cr 25 Mo 9 B 13 C 3 metallic glass (FMG) particles reinforced 7075 aluminum matrix (Al-7075) composites were prepared by spark plasma sintering (SPS) technique. The microstructure of the composites showed good interface bonding between the FMG particles and the matrix. The micro-hardness of the composite with 30 vol% FMG particles reached 160.63 HV, which was increased by 30% compared with that of Al-7075 (119.3 HV). The ultimate compression strength (UCS) of the composite was also improved significantly from 596 MPa for Al-7075 matrix to 749 MPa for the composite reinforced with 30 vol% FMG particles, and the compression strain of the composite reached 22%. These results indicate that the mechanical properties of the composites can be enhanced by adding high volume fraction FMG particles. The enhancement of the strength is resulted from multiple strengthening mechanisms, and the main contributions come from the thermal mismatch and grain refinement. [ABSTRACT FROM AUTHOR]

Fe–Cr–Mo–B–C amorphous powders are usually used in thermal spraying, spark plasma sintering or 3D printing to prepare coatings or large-sized bulk amorphous alloys. However, their non-isothermal crystallization kinetics is far from being investigated in detail because of their relatively complicated crystallization behavior. In this work, the phase evolution, crystallization kinetics and crystallization mechanism of Fe–Cr–Mo–B–C (Cr: 25–27 wt%, Mo: 16–18 wt%, B: 2–2.2 wt%, C: 2–2.5 wt%) amorphous powder during non-isothermal crystallization are analyzed by X-ray diffraction, scanning electron microscope and differential scanning calorimetry together with Ozawa method and local Avrami exponent. The peak temperature of the first precipitated phase is less sensitive to the heating rate. In the non-isothermal crystallization process upon constant-rate heating to elevated temperatures the phase sequence is: α -Fe, M 23 (C, B) 6 , M 7 C 3 and FeMo 2 B 2 (M = Fe, Cr, Mo). The apparent activation energy of crystallization of the amorphous powders obtained using Kissinger's method is between 385 and 557 kJ/mol, which is higher than that of most iron-based amorphous alloys reported so far, indicating a relatively high stability against crystallization. a -Fe and FeMo 2 B 2 have a similar transformation mechanism: the early phase transition is completed by diffusion controlled growth with an increasing nucleation rate; as the crystallized volume fraction increases, the nucleation rate decreases, and nucleation does not occur even in the later stage of crystallization. The crystallization mechanism of M 23 (C, B) 6 and M 7 C 3 is similar: when the crystallized volume fraction α is higher than 0.1, only crystal growth occurs. This might be due to the fact that the large number of interfaces formed between the early precipitated phase and the amorphous matrix promote nucleation, rendering nucleation complete at the stage when the crystallized volume fraction α is less than 0.1. Therefore, the first and fourth crystallization events are diffusion controlled, the second and third crystallization events are primarily governed by grain growth. • A Fe–Cr–Mo–B–C amorphous powder was successfully prepared by atomization. • The amorphous alloy has a high resistance to crystallization. • The crystallization process is controlled by diffusion. [ABSTRACT FROM AUTHOR]