Heterogeneous fiberous structured Mg-Zn-Zr alloy with superior strength-ductility synergy

Here we reported a heterogeneous fiberous structured Mg-5.6Zn-0.6Zr(wt%)alloy obtained by conventional extrusion method,which exhibited high yield strength of∼345 MPa,ultimate tensile strength of∼370 MPa,and high tensile strain of∼20.5%,superior to most of the Mg-Zn based alloys reported so far.The extraordinarily high mechanical properties were mainly attributed to the heterogeneous fiberous structure consisting of alternating coarse-and fine-grain layers.Grains in the different layers grew into the neighboring layers,ensuring a good layer bonding.A high Schmid factor and geometric compatibility factor for pyramidal slip led to full slip transfer between the neighboring coarse grains and fine grains,which could help to release the stress concentration and avoid early fracture.The profuse acti-vated<c+a>glide dislocations could render the unprecedented high tensile strain.The constraint by the hard fine-grain domains made the soft coarse-grain domains strong like the hard fine-grain domains,as well as the nanoscale precipitates pinning dislocations,contributed to the high strength.The hetero-geneous microstructure design was shown to have synergistic improvement in strength-ductility balance,which could be an inspiring strategy to improve mechanical properties of hexagonal close-packed(hcp)metals.

Interfacial Banded Transcrystallization of Polyoxymethylene/Poly(butylene succinate) Blends Induced by the Polyamide 6 Fiber

Interfacial crystallization of polyoxymethylene/poly(butylene succinate)blends induced by the polyamide 6(PA6)fiber was investigated.Due to strong heterogeneous nucleating ability,dense nuclei were generated on the surface of the PA6 fiber,which compelled the growth of twisted lamellae perpendicular to the PA6 fiber.As a result,unique interfacial banded transcrystallization was formed,which is rarely found before.Crystallization temperature was dominant in determining the nucleation activity of the PA6 fiber,further affecting the architecture of banded transcrystallization.With the increase of crystallization temperature,the nucleation density decreased to give more growth space for the twisted lamellae around the fiber.The wave-like banded stripes were transformed into fan-like stripes.Accordingly,band spacing and eccentricity respectively showed positive and negative correlation with crystallization temperature.These meaningful results shed light on regulating the architecture of banded crystals in polymer composites.