A B S T R A C TIn the present study, quasi-static and dynamic shear response of 301 stainless steel (SS) with gradient structure (GS) and heterogeneous lamella structure (HLS) were investigated by uniaxial tensile tests and Hopkinson-bar tests with hat-shaped specimens. The 301 SS with GS and HLS show a good combination of strength and ductility under quasi-static tensile tests, which is due to the back stress hardening for heterogeneous structures. Before the formation of adiabatic shear band (ASB), the dynamic shear response of 301 SS with coarse-grained (CG) austenitic structure shows a strong linear hardening stage and a plateau stage, which are due to the martensite transformation and the continuous deformation through strain partitioning between different phases, respectively. For 301 SS with CG austenitic structure, the grain size was observed to significantly refined in the ASB, while the reverse phase transformation occurs and the austenite phase increases significantly again in the ASB with increasing shear displacement, resulting in a hardness valley in the ASB at the shear displacement of 2.0 mm. The GS and HLS show excellent dynamic shear properties, this could be due to the back stress hardening for either macroscopically or microscopically heterogeneous structures. The HLS seems to have better impact shear properties than the GS, which indicates that the HLS with microscopically heterogeneous structures could delay the formation of ASB in a better way than the GS with macroscopically heterogeneous structures. The results in the current study could provide insights for obtaining better mechanical properties under dynamic conditions.
Defatted Schizochytrium sp. (DS) is a by‐product of algae oil, which is rich in docosahexaenoic acid (DHA). In this study, five DS‐supplemented diets, including 0 (DS0), 30 (DS3), 60 (DS6), 90 (DS9) and 120 (DS12) g/kg, were used to evaluate the effects of dietary DS on juvenile mirror carp (Cyprinus carpio var. specularis). A total of 270 fish juvenile mirror carp (8.55 g/tail, eighteen fish per cage) were fed with five isonitrogenous and isolipidic diets for 8 weeks. The results showed that final body weight (FBW), weight gain (WG) and specific growth rate (SGR) first increased in DS6 group (p > 0.05) and then significantly decreased in DS12 group (p < 0.05). There were significantly higher crude protein (CP) and lower crude lipid (CL) levels in whole body and hepatopancreas of fish fed with DS6 and DS9 diets than those with DS0 and DS3 diets (p < 0.05). The level of DHA in the muscle, hepatopancreas and whole body was significantly increased by higher DS‐supplemented diets (DS6, DS9 and DS12) than that of the control group (p < 0.05). The atherogenic index (AI) and thrombosis index (TI) in the muscle of all treatment groups were significantly lower than those of the control group, while the hypocholesterolaemic/hypercholesterolaemic fatty acid ratio (h / H) index of treatment groups was significantly higher than that of the control group (p < 0.05).The height of fore‐intestinal villi of DS3 and DS6 groups was significantly higher than that in the control group (p < 0.05). Moreover, superoxide dismutase (SOD) activity of the serum and hepatopancreas in DS6, DS9 and DS12 groups was significantly higher than that in the control group (p < 0.05). Analyses based on the special growth rate and antioxidant status index revealed that the suitable DS range was 4.18%–6.00% (41.08–60 g/kg), which could improve the growth performance and health status of mirror carp.
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