Search

Zr–Co–Al alloys are widely used due to their good biocompatibility and high-pressure properties. In the present work, the Zr 54.5 Co 33.5 Al 12 alloy was prepared by rapid solidification. It has been found that the central region (b region) and the edge region (d region) have obvious changes in the microstructure, with the b region contains a large number of crystalline phases, and the d region can obviously observe the morphology of the amorphous state except a few dendrites. A certain amount of amorphous is contained in the d region as detected by XRD analysis. The fracture strength can undoubtedly reach up to 2031 MPa and the fracture strain is about 1.8 %. TEM analysis revealed the B2-to-B33 phase transition in the deformed alloy, and a significant number of nanotwins with a {111} <121> type of twin relationship were observed in the B33 ZrCo phase. Furthermore, the stacking fault energy (SFE) for varying applied stresses was calculated. From the calculation results, the negative SFE (about −41 mJ/m2) is beneficial to the B2-to-B33 phase transition, and it is known that twin thickness decreases with decreasing SFE. • The negative stacking fault energy is beneficial to the B2-to-B33 phase transition. • The twin thicknesses on B33 phase decrease with a reduction in stacking fault energy. • B2-to-B33 martensitic transformation can effectively improve the mechanical properties of Zr 54.5 Co 33.5 Al 12 alloy. [ABSTRACT FROM AUTHOR]

• 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]

Abstract Most bulk metallic glass systems with high glass-forming ability are doped with precious metal(s) or toxic element(s), like palladium and beryllium, leading to relatively high cost or low safety in use. In this work, the glass-forming ability, crystallization kinetics and mechanical properties of the Zr 55 Co 25 Al 20 and Zr 52 Co 25 Al 23 bulk metallic glasses prepared by water-cooled copper mold suction casting are investigated in detail. The results show that Zr 52 Co 25 Al 23 has a wider supercooled liquid region, a higher thermal stability and a higher glass-forming ability than the Zr 55 Co 25 Al 20 amorphous alloy. At the same time, Zr 52 Co 25 Al 23 has a higher activation energy of crystallization than Zr 55 Co 25 Al 20 amorphous alloy, indicating that Zr 52 Co 25 Al 23 has a higher resistance to crystallization than Zr 55 Co 25 Al 20. Investigation of the mechanical properties reveals that Zr 52 Co 25 Al 23 also has a higher fracture strength of up to 2308 MPa and a higher specific fracture strength of up to 3.78 × 105 N m kg−1 compared with 316L stainless steel, Ti-6Al-4V, as well as Mg-, Ti-, and other Zr-based BMGs. Graphical abstract Image 1 Highlights • Zr 52 Co 25 Al 23 (Zr52) and Zr 55 Co 25 Al 20 (Zr55) amorphous alloys were investigated. • Lower Zr/Al ratio leads to a wider SLR, higher thermal stability and higher GFA. • Zr52 has a higher resistance to crystallization than Zr55. • Zr52 has larger plasticity and higher specific strength than Zr55. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ growing carbon nanotubes (CNTs) on the surface of Ti particles prepared a novel CNTs@Ti hybrid reinforcement. • CNTs with good structural integrity were evenly dispersed into the Al matrix owing to the carrying effect of Ti particles. • The precipitation of nano-scaled TiC, Al 4 C 3 and TiAl 3 enhanced the interface bonding of CNT/Al. • The high strength of composite can attribute to the multi-phase coupling synergistic strengthening effect. The strengthening effect of carbon nanotubes (CNTs) in Al matrix composites (AMCs) is significantly weakened by CNTs agglomeration and unsubstantial interfacial bonding with the Al matrix. In this study, CNTs were grown on the surface of Ti particles by chemical vapor deposition to obtain CNTs@Ti hybrid reinforcement, followed by powder metallurgy to prepare CNTs@Ti/Al composites. Evenly dispersed CNTs with good structural integrity were successfully obtained using the carrying effect of the micron-sized Ti particles. Meanwhile, TiC, Al 4 C 3 , and TiAl 3 were generated at the CNT/Al interface, which strengthened the bearing capacity of the inner-wall of the CNTs, improved the wettability of the CNT/Al interface, and enhanced the strain-hardening ability of the Al matrix. The deficiencies in the CNTs/Al composites are compensated by this kind of materials design, and the two types of reinforcements have a synergistic strengthening effect, which greatly improves the comprehensive mechanical properties of AMCs. An excellent interface structure is formed by controlling the interface reaction such that the dispersion, grain boundary, dislocation, and load transfer strengthening mechanisms are fully realized. [ABSTRACT FROM AUTHOR]

Aluminum matrix composites (AMCs) reinforced with novel carbon nanotube (CNT)-Fe-based metallic glass (FMG) synergistic reinforcements were successfully prepared by powder metallurgy. The CNT-FMG reinforcements were obtained by growing CNTs on the surface of FMG particles using chemical vapor deposition (CVD). By controlling the catalytic temperature, the grown CNTs exhibited good morphology, a high degree of graphitization, and thermal oxidation stability. CNTs were homogeneously dispersed in the Al matrix through the carrying action of FMG particles. The CNT-FMG synergistic reinforcements significantly improved the mechanical properties of the composite, and formed a tight interfacial bonding with the Al matrix. The CNT-FMG reinforcements had a remarkable synergistic strengthening effect on the composite. • CNTs were grown on the surface of FMG particles by chemical vapor deposition. • CNT-FMG synergistic reinforced Al matrix composites were prepared. • CNTs were homogeneously dispersed in Al matrix through the carrying of FMG. • CNT-FMG contributed remarkable synergistic strengthening effect to the composite. [ABSTRACT FROM AUTHOR]