Potassium fertilizer promotes the thin-shelled Tartary buckwheat yield by delaying senescence and promoting grain filling.

The application rate of potassium fertilizer is closely related to the yield of crops. Thin-shelled Tartary buckwheat is a new variety of Tartary buckwheat with the advantages of thin shell and easy shelling. However, little is known about application rate of potassium fertilizer on the yield formation of thin-shelled Tartary buckwheat. This study aimed to clarify the effect of potassium fertilizer on the growth and yield of thin-shelled Tartary buckwheat. A field experiment to investigate the characteristics was conducted across two years using thin-shelled Tartary buckwheat (Miku 18) with four potassium fertilizer applications including 0 (no potassium fertilizer, CK), 15 (low-concentration potassium fertilizer, LK), 30 (medium-concentration potassium fertilizer, MK), and 45 kg·ha-1 (high-concentration potassium fertilizer, HK). The maximum and average grain filling rates; starch synthase activity; superoxide dismutase and peroxidase activities in leaves; root morphological indices and activities; available nitrogen, phosphorus, and organic matter content in rhizosphere soil; urease and alkaline phosphatase activities in rhizosphere soil; plant height, main stem node number, main stem branch number, leaf number; grain number per plant, grain weight per plant, and 100-grain weight increased first and then decreased with the increase in potassium fertilizer application rate and reached the maximum at MK treatment. The content of malondialdehyde was significantly lower in MK treatment than in other three treatments. The yields of thin-shelled Tartary buckwheat treated with LK, MK, and HK were 1.22, 1.37, and 1.07 times that of CK, respectively. In summary, an appropriate potassium fertilizer treatment (30kg·ha-1) can delay the senescence, promote the grain filling, and increase the grain weight and final yield of thin-shelled Tartary buckwheat. This treatment is recommended to be used in production to achieve high-yield cultivation of thin-shelled Tartary buckwheat.

Increasing planting density can improve the yield of Tartary buckwheat.

Planting densities and nitrogen fertilizer application rates determine the yield of crops. Tartary buckwheat is a pseudocereal crop with great health care and development values. However, little is known about application of nitrogen fertilizer and planting density on the physiological characteristics of Tartary buckwheat. This study aims to clarify the effect of planting density on the senescence and yield of Tartary buckwheat under low nitrogen conditions. A 2-year field experiment was conducted on Tartary buckwheat (Jinqiao 2) to study the effects of different planting densities (8 × 105, 10 × 105, 12 × 105, 14 × 105, and 16 × 105 plants·ha-1) on the root morphology and activity, chlorophyll and malondialdehyde (MDA) contents, antioxidant enzyme activity, photosynthetic characteristics, agronomic traits, and yield of Tartary buckwheat in the absence of nitrogen fertilizer treatment. With the increase in planting density, the root morphological indices and activities; chlorophyll a, chlorophyll b, and carotenoid contents; superoxide dismutase and peroxidase activities; net photosynthetic rate; transpiration rate; intercellular CO2 concentration and transpiration rate; main stem node, branch, and leaf numbers; grain number and weight per plant; and 1000-grain weight of Jinqiao 2 decreased continuously, whereas plant height and leaf MDA content increased continuously. The yield of Tartary buckwheat first increased and then decreased with the increase in planting density. The yield under 14 × 105 plants·ha-1 treatment increased by 68.61%, 44.82%, 11.00%, and 22.36%, respectively, relative to that under 8 × 105, 10 × 105, 12 × 105, and 16 × 105 plants·ha-1treatments. In summary, planting at an appropriately high density (14 × 105 plants·ha-1) can promote the increase in the yield of Tartary buckwheat populations under low nitrogen conditions and is recommended for use in production to achieve the high-yielding and nitrogen saving cultivation of Tartary buckwheat. This research can serve as a theoretical basis to jointly achieve the high yield and nitrogen saving of Tartary buckwheat.

Selective Laser Melting Additive Manufactured Tantalum: Effect of Microstructure and Impurities on the Strengthening-Toughing Mechanism.

The balance between the strength and the toughness of pure tantalum (Ta) fabricated with selective laser melting (SLM) additive manufacturing is a major challenge due to the defect generation and affinity for oxygen and nitrogen. This study investigated the effects of energy density and post-vacuum annealing on the relative density and microstructure of SLMed tantalum. The influences of microstructure and impurities on strength and toughness were mainly analyzed. The results indicated that the toughness of SLMed tantalum significantly increased due to a reduction in pore defects and oxygen-nitrogen impurities, with energy density decreasing from 342 J/mm3 to 190 J/mm3. The oxygen impurities mainly stemmed from the gas inclusions of tantalum powders, while nitrogen impurities were mainly from the chemical reaction between the molten liquid tantalum and nitrogen in the atmosphere. The proportion of <110> texture decreased after vacuum-annealing at 1200 °C, while that of the <100> texture increased. Concurrently, the density of dislocations and small-angle grain boundaries significantly decreased while the resistance of the deformation dislocation slip was significantly reduced, enhancing the fractured elongation up to 28% at the expense of 14% tensile strength.

Effects of Plasma ZrN Metallurgy and Shot Peening Duplex Treatment on Fretting Wear and Fretting Fatigue Behavior of Ti6Al4V Alloy.

A metallurgical zirconium nitride (ZrN) layer was fabricated using glow metallurgy using nitriding with zirconiuming prior treatment of the Ti6Al4V alloy. The microstructure, composition and microhardness of the corresponding layer were studied. The influence of this treatment on fretting wear (FW) and fretting fatigue (FF) behavior of the Ti6Al4V alloy was studied. The composite layer consisted of an 8-µm-thick ZrN compound layer and a 50-µm-thick nitrogen-rich Zr-Ti solid solution layer. The surface microhardness of the composite layer is 1775 HK0.1. A gradient in cross-sectional microhardness distribution exists in the layer. The plasma ZrN metallurgical layer improves the FW resistance of the Ti6Al4V alloy, but reduces the base FF resistance. This occurs because the improvement in surface hardness results in lowering of the toughness and increasing in the notch sensitivity. Compared with shot peening treatment, plasma ZrN metallurgy and shot peening composite treatment improves the FW resistance and enhances the FF resistance of the Ti6Al4V alloy. This is attributed to the introduction of a compressive stress field. The combination of toughness, strength, FW resistance and fatigue resistance enhance the FF resistance for titanium alloy.

Effects of WC-17Co Coating Combined with Shot Peening Treatment on Fatigue Behaviors of TC21 Titanium Alloy.

The improvement and mechanism of the fatigue resistance of TC21 high-strength titanium alloy with a high velocity oxygen fuel (HVOF) sprayed WC-17Co coating was investigated. X-ray diffraction (XRD) and the corresponding stress measurement instrument, a surface roughness tester, a micro-hardness tester, and a scanning electron microscope (SEM) were used to determine the properties of the HVOF WC-17Co coating with or without shot peening. The fatigue behavior of the TC21 titanium alloy with or without the WC-17Co coating was determined by using a rotating bending fatigue testing machine. The results revealed that the polished HVOF sprayed WC-17Co coating had almost the same fatigue resistance as the TC21 titanium alloy substrate. This resulted from the polishing-induced residual surface compressive stress and a decrease in the stress concentration on the surface of the coating. Moderate-intensity shot peening of the polished WC-17Co coatings resulted in significant improvement of the fatigue resistance of the alloy. Furthermore, the fatigue life was substantially higher than that of the substrate, owing to the deep distribution of residual stress and high compressive stress induced by shot peening. The improved surface toughness of the coating can effectively delay the initiation of fatigue crack propagation.