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Abstract The fragmentation and interfacial stress transfer of Cu 75 Zr 25 amorphous films with varying film thickness (h) on polyimide substrates were systematically investigated by using uniaxial tensile testing, in combination with in situ optical microscope and atomic force microscope characterizations. It is revealed that the interfacial stress transfer length increases monotonically as h increases. The interfacial stress transfer mechanism changes from elastic-plastic to approximately linear elastic at a critical point of h = 250 nm. This is related to h -dependent deformation-induced devitrification (DID) near the interfaces that the thinner Cu-Zr amorphous films display more DID. This study elucidates for the first time the effect of DID on the interfacial stress transfer, which will be helpful to design the interface with desired property for nanotechnological applications. Highlights • Fragmentation and interfacial stress transfer of Cu-Zr amorphous films were studied. • Interfacial stress transfer length increases as film thickness increases. • Thinner Cu-Zr amorphous films display more deformation-induced devitrification. • A crystallization gradient is induced by deformation along the film growth direction. • Interfacial stress transfer changes from elastic-plastic to linear elastic. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) reinforced magnesium matrix composite prepared by an improved process was extruded at 350°C with an extrusion ratio of 20:1. Most CNTs were individually and uniformly dispersed in the as-cast and the as-extruded composites. Moreover, good interfacial bonding was achieved, and Raman spectroscopy showed that the damage to CNTs was insignificant. The addition of CNTs could weaken basal plane texture. Meanwhile, the CNTs evidently improved the ultimate tensile strength, yield strength and Young's modulus of the as-extruded composite. Pulling-out CNTs proved that the length of the CNTs was not large enough to be compatible with the high strength of the CNTs. Grain refinement, load transfer mechanism and Orowan strengthening mechanism play important roles on the increase of the yield strength. The composites fabricated by our process showed high strengthening efficiency of CNTs. [ABSTRACT FROM AUTHOR]

Abstract In this paper we investigated the viscosity and density of melts Fe 73.5 Cu 1 M 3 Si 13,5 B 9 where M = Nb, Mo, V, Cr. It is shown that the lowest viscosity and activation energy of viscous flow has a melt with Nb, whose atomic radius is the largest. It is shown that the free volume of the melt is higher during cooling compared to heating, and it indicates irreversible structural changes in the melt. The critical temperature T k = 1770 K is found, above which the activation energy of the viscous flow changes. Highlights • Relationship of melt viscosity with the size of embedded atoms. • The critical temperature of change in the activation energy of the viscous flow. • Temperature dependence of free volume during heating and cooling of the melt. [ABSTRACT FROM AUTHOR]

The (micron[m]+submicron[s]+nano[n]) SiC particles (SiCp) reinforced AZ31B magnesium matrix composites (AZ31B/SiCp/m + s + n composites) were fabricated by stirring casting technology followed by hot extrusion. This method has successfully solved the homodisperse problem of SiCp/m + s + n in the magnesium matrix composites. The influence of SiCp/m + s + n on the dynamic recrystallization (DRX) behavior of the magnesium matrix was investigated by researching the TEM microstructures of composites. The results indicated that the addition of SiCp/m + s + n was helpful to increase the ratio of DRXed nucleation and reduce the average grain size of matrix. The particle deformation zone (PDZ) can be formed in the vicinity of micron SiCp, while the region with high dislocation density can be created around submicron SiCp owing to pin dislocation and deformation mismatch between matrix and particles. These regions are ideal sites for the formation of recrystallization nucleus. Meanwhile, the addition of fine SiCp(nano and submicron) may delay or hinder the growth of matrix grain through the pinning effect on the grain boundaries during hot extrusion. The tensile test indicates that the strength of the AZ31B/SiCp/m + s + n composites has a significant improvement. Compared with the single sized or bimodal sized particles reinforced magnesium matrix composites, the tensile strength of the AZ31B/SiCp/m + s + n composites were highlighted. [ABSTRACT FROM AUTHOR]

The effect of fly ash cenospheres (FACs) on the electromagnetic interference (EMI) shielding effectiveness (SE) of the magnesium matrix was investigated. Raw FACs and FACs modified by Ca(OH) 2 were employed as reinforcements. The two kinds of FACs dispersed uniformly in the matrix. Most unmodified FACs were severely broken in the composites, but the majority of FACs kept complete integrated in the composites reinforced by modified FACs. In the range of the testing frequency, raw FACs did not evidently improve the EMI SE of matrix. However, the modified FACs with better ball structure improved the EMI SE of matrix to 75–90 dB. This improvement is attributed to the reflection loss occurred at the outer face (R), absorption at interior place (A) of the composites as well as multiple reflection (B) between different modified FACs. [ABSTRACT FROM AUTHOR]

A particulate reinforced magnesium matrix nanocomposite was subjected to multidirectional forging (MDF). The results showed that the microstructure of the nanocomposite mainly consisted of some large initial grains and fine recrystallized grains along initial grain boundaries after 1 MDF pass. With increasing the MDF passes, the degree of dynamic recrystallization increased and ultrafine grains with average size of about 20 nm were observed in the nanocomposites after 6 MDF passes. The distribution of SiC nanoparticles in the nanocomposite was homogeneous outside some SiC nanoparticle dense zones after different MDF passes. Compared with typical basal texture obtained for 1 MDF pass, the basal pole intensity decreased firstly for 3 MDF pass and then increased for 6 MDF passes. Both ultimate tensile strength and elongation to fracture of the nanocomposite were enhanced with increasing the MDF passes, while yield strength decreased after 3 MDF passes and then increased slightly after 6 MDF passes. [ABSTRACT FROM AUTHOR]

The present study dealt with the AZ91 alloy subjected to multidirectional forging (MDF) under decreasing temperature conditions with emphasizing on relationship between microstructures and mechanical properties generated by MDF. The obtained results showed that grains of the alloy were gradually refined while the amount of the second phase precipitated along the grain boundaries was increased with increasing the MDF passes and decreasing the MDF temperature. Compared with the as-cast alloy, yield strength, ultimate tensile strength and elongation of the AZ91 alloy after MDF under decreasing temperature conditions were simultaneously increased. As the numbers of MDF passes were gradually increased and the MDF temperature was gradually decreased, the yield strength was gradually decreased, suggesting that texture softening may overwhelm the strengthening due to the grain refinement as well as the homogeneous distribution of precipitates. [ABSTRACT FROM AUTHOR]