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While titanium (Ti) alloys offer significant advantages, such as high strength and corrosion resistance, their widespread utilization in various engineering sectors is hindered by their prohibitively high cost, which is attributed to expensive equipment and complex preparation processes. The present study centered on assessing the influence of multi-pass hot rolling, a commonly available industrial process, on the microstructure and mechanical properties of sintered powder metallurgy commercially pure Ti (cp-Ti). With increasing levels of accumulated deformation, the rolled materials exhibited a refined grain size, the formation of twins, and a reduced residual porosity, resulting in a tailored microstructure that enhanced the material's balance between strength and ductility. The ultimate tensile strength reached 574.8 MPa, with an elongation at break of 28.1%. The hardness peaked at 196.4 HV.

To improve the performance of the urease inhibitor (UI) N-butyl thiophosphorothioate triamine (NBPT) in various fertilizer applications, we combined the humic acid (HA) from coal and NBPT with urea to preliminarily evaluate the effect of HA on the degradation and effectiveness of NBPT. An incubation experiment was conducted in black soil (Chernozem, FAO) and heilu soil (Calcic Kastanozem, FAO), and the NBPT content, urea-nitrogen (N) transformation, enzyme activity related to N transformation and microbial biomass carbon (MBC) content were measured. The results showed that combining NBPT and HA had opposite effects in different soils. In heilu soil, HA delayed the degradation of NBPT, and urea hydrolysis was delayed by approximately 65 days. In black soil, HA accelerated the degradation of NBPT and increased soil urease activity and the MBC content. We concluded that differences in soil MBC content and pH led to differences in the effect of HA on NBPT and that a rapid increase in microbial carbon content caused by HA in black soils led to a faster rate of NBPT degradation. However, the underlying mechanism must be further investigated. In different soils, we concluded that HA affects the effectiveness of NBPT by changing the half-life of NBPT; moreover, the effectiveness of the formulation should be verified in field experiments.

The present work proposes a novel master-alloy pre-hydrogenation powder metallurgy (MAPH) method to fabricate the TC16 (Ti-3Al-5Mo-4.5V) alloy, which overcomes the challenge of low sintering density due to the high percentage of alloying powders (APs) and the presence of Mo element. The relative density of sintered TC16 alloys increases with the Ti-addition in APs, i.e., ∼99.2% and ∼99.4% for sintered TC16 alloys based on pre-hydrogenated 7.5Ti-3Al-5Mo-4.5V (7.5TiMA-Hx) and 12.5Ti-3Al-5Mo-4.5V (12.5TiMA-Hx) powders, respectively. The APs were successfully modified to be brittle and hydrogen-containing, which exhibits similar pressing and sintering characteristics as TiH2powders. The increased relative density could be ascribed to the brittleness of 7.5/12.5TiMA-Hx, in which particles show sharp corners that can form interlocked structures with TiH2particles during pressing. Furthermore, the 7.5/12.5TiMA-Hxand TiH2powder particles release H2and shrink simultaneously during sintering, which minimizes the difference in volume mismatch between particles and promotes elemental diffusion. The sintered TC16-7.5TiMA-Hxalloy achieves excellent mechanical properties, i.e., an ultimate tensile strength of ∼1004.6 MPa, a yield strength of ∼934.2 MPa and an elongation of ∼15.8%, due to the low porosity and acceptable impurity contents. However, the excessive O and N elements in the sintered TC16-12.5TiMA-Hxalloy can induce premature intergranular fracture, resulting in decreased ductility. Therefore, the innovative MAPH technique is promising in obtaining high density sintered Ti alloys with excellent mechanical properties.

Introducing coherent twin boundaries is an effective way to develop submicron/nano-sized grains with improved thermal stability in polycrystals, which exhibit enhanced mechanical properties of metals, such as high strength, high hardness and high fracture toughness. However, crystalline defects, such as dislocations and disclinations, usually arise at twin boundary junctions, which lead to local stress concentration and property degradation. Here we show that a large number of high-index coherent twin boundaries (e.g., Σ11 and Σ19a) can be produced through a well-controlled deformation twinning process. By using metastable β-Ti alloys as an example and analyzing the broken symmetry associated with deformation twinning, we demonstrate that the abnormal high-index twins result from intercorrelated twinning pathways and twin-twin reactions. The formation mechanism of self-organized multi-twin structures has been analyzed systematically through phase field modeling and simulations. It has been found that, under well designed thermo-mechanical condition, regularly distributed high-index twin boundaries and geometrically-compatible twin boundary junctions (i.e., dislocation/disclination-free) can be produced. The stress/strain condition required to obtain self-organized twins has been quantitatively determined, which provides a theoretical guideline for the development of self-organized submicron/nano-twin metals for unprecedented properties.

The present study investigated the effects of heat treatment (solid solution and aging treatments) on the microstructure and mechanical properties of a hot-rolled α+β Ti–3Al–5Mo–4.5V (TC16) produced through blended elemental powder metallurgy (BEPM) process using master alloy hydrogenation (MAH) approach. After solid solution treatment, metastable martensite α'' phase and athermal ω phase were formed. Aging treatment facilitated decomposition of metastable phases and precipitation of αsparticles. Dispersion strengthening, resulting from the formation of a significant amount of α/β interfaces between fine secondary αsparticles and β matrix, played a decisive role in enhancing the strength of the TC16 alloy. However, elevated aging temperatures promoted the coarsening of αsparticles, leading to a reduction in the strengthening effect. A systematic investigation of the effects of the solid solution and aging treatments enabled the evolution of a bimodal microstructure with the precipitation of fine αsparticles, contributing to an outstanding combination of strength and ductility. The ultimate tensile strength reached 1424.6 MPa with an elongation at break of 7.7%, while the hardness reached 380.2HV.

Graphic abstract:

• A cost-effective strategy was suggested to produce high-performance near-β titanium alloy. • A excellent balance of strength and ductility (1570 MPa, 6.1%) was obtained. • A relationship between strength and Vickers hardness was established to analyze the negative influence of residual pores. • Under negative influence of residual pores, the evolution of tensile and fatigue properties was analyzed. Heat treatment plays an important role in tailoring the mechanical properties of powder-metallurgy (PM) titanium alloys. However, only limited work about the rapid heat treatment (RHT) of PM titanium alloys has been reported. In this work, RHT was applied to PM Ti–5Al–5Mo–5V–1Cr–1Fe alloy after hot rolling to study the evolution of its mechanical properties and the influence of residual pores on its properties. Through hot rolling and annealing, a fine and uniform α + β structure with few residual pores is obtained. During RHT, the primary α dissolves gradually and completes in the β region, and the β grains then grow, resulting in the continuous decrease in elongation after aging. Moreover, the tensile strength first increases and then decreases with increasing RHT temperature, owing to the increase in volume fraction of secondary α in α + β region and the β grain growth in β region. In contrast to the RHT of cast-and-wrought titanium, the negative influence of residual pores lowers the RHT temperature for obtaining the highest tensile strength to a temperature below the β-transus temperature. Despite the negative influence of the residual pores, retained primary α and fine β grains with fine secondary α inside contribute to achieving a good strength/ductility balance (1570 MPa and 6.1%, respectively). Additionally, although at higher cycles to failure, the negative influence of residual pores increases as it affects the crack initiation zone at the subsurface, the good resistance of secondary α to fatigue crack propagation still enhances the fatigue strength considerably (about 300 MPa). This work suggests a cost-effective strategy to produce titanium alloys with high performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Starting microstructure with nonuniform micro-scale grains is designed for the study of microstructure and mechanical properties after rapid heat treatment (RHT) and subsequent aging. RHT was used to retard β grain growth in single-phase β region, while RHT and aging parameters affected size of secondary α and, hence, tensile strength and ductile characteristics. Heating rate for aging is important parameter affecting ω phase precipitation, which, in turn, affects the size of secondary α. Fast heating for aging avoided formation of ω phase, while ω phase formed at slow heating and duplex aging conditions results in refined α precipitations. After single-step aging with fast heating rate, proved by the calculation of strength based on the strengthening mechanism, the RHT temperature for the highest strength is at the bottom of single-phase β region. However, the nonuniformity of starting grain size results in the nonuniform β grain size after RHT, which affects the strengthening and elongation negatively. Proper selection of RHT parameters and fast heating for subsequent aging leads to refined secondary α and high balance of tensile properties (1415 MPa, 5.2%). Formation of ω phase at slow heating and at duplex aging resulted in marked drop in ductility with some variation of strength level (1344 MPa, 2.2%, and 1433 MPa, 0.7% correspondingly). Homogenising of the starting grain size by decreasing the β solution treatment temperature leads to achievement of the best tensile properties (1480 ± 12.5 MPa, 8.2% ± 0.99%).

Dissolution of nanoparticles (NPs) determines the fate and subsequently the actual exposure of biota to the NPs. Whether and to what extent NPs dissolve or remain in their particulate form in aqueous media is thus of pivotal knowledge for the safety assessments of NPs. In this research, secondary data on dissolution of NPs were systematically collected. A range of dissolution rates could be recalculated, as dependent on the characteristics of the NPs and the exposure medium. For example, two nanoparticles which are identical in terms of chemical composition of the particle core and of the coating, had a fully different dissolution behaviour, as subject to different surface modifications. A model was derived for calculating dissolution rate constants of NPs. The model is based on the initial kinetics of dissolution of NPs under different exposure scenarios and on the assumption of pseudo-first order reaction kinetics at the particle surface. Characterizing the dissolution rates and the parameters which modify dissolution allows for grouping of those NPs that dissolve either very slowly or very quickly. This information can be used for risk assessment of NPs, and once sufficient kinetic dissolution data are available, will ultimately allow for development of predictive models for the dissolution kinetics of newly developed nanomaterials.

Nozzleless housings for turbocharger turbines accelerate and guide flow into downstream rotors. Their design affects the aerodynamic performance and reliability of the turbines. Due to the three-dimensional nature of the volute of the housings, turbine housing volute design is largely based on extended 1D theories and trial-and-error method. In this paper, a detailed description of an extended two-dimensional theory for volute design is given, including its numerical implementation. The method is then applied to design a twin-entry turbine housing for a turbocharger turbine under both equal and unequal admissions, to replace a highly optimized, manually designed housing. The results show that the new volute achieves the same turbine aerodynamic performance as the manually optimized volute with greatly reduced design time, and it also generates more uniform rotor inlet condition with lower pressure excitation force. A breakdown of the stage loss shows that the loss in the new volute housing is larger than that in the manual housing due to its smaller overall dimensions, but the losses inside rotor and downstream diffuser are both reduced due to the more uniform volute exit flow. A discussion on the secondary flow in the two volutes is carried out to show how the volute geometry, through influencing the radial discharge from the volute exit, affects this flow. A further discussion on the flow angle jump around the tongue is placed at the end of the paper to show the mechanism of this jump, how to control it in volute design, and to offer a way forward to improve the volute design method.

In this letter, we consider a multi-server mobile edge computing (MEC) network where a user with limited computation ability aims to complete an intensive computation task in a short time under the help of multiple edge servers. We study the delay-minimization offloading schemes with and without user’s energy constraint, which involve the joint optimization of task allocation ratio for local computation, the wireless offloading manner (i.e., non-orthogonal multiple access (NOMA) offloading or single-server offloading mode), and the server pair selection. Specifically, the joint optimal solutions are derived in semi-closed forms and the critical conditions of switching offloading manners are derived in closed form. Numerical results corroborate the superiority of our proposed offloading scheme in terms of overall latency under various settings.

Chelating agent is known as the enhancer for metal phytoextraction; however, there is still a lack of efficient and environmentally sustainable chelators. Here, lemon residue extraction (LRE), prepared from 11 kinds of fruit wastes, was combined with N, N-bis (carboxymethyl) glutamic acid (GLDA), and tea saponin (T.S.) for the compounded plant-derived chelator (CPC), and their influences on Cd phytoextraction by the hyperaccumulator Sedum alfrediiwas evaluated. Among these fruits, the lemon residue extracted the most significant amount of Cd from the soil. The most effective CPC was at the volume ratio of three agents being 15:4:1 (LRE:GLDA:T.S.). Compared with the deionized water, the solubility of three Cd minerals was increased by 85–256 times, and Cd speciation was substantially altered after CPC application. In the pot experiment, CPC addition caused evident increases in plant shoot biomass, Cd phytoextraction efficiency, and organic matter content compared with EDTA and nitrilotriacetic acid (NTA) application. CPC induced fewer changes in bacterial community composition compared with EDTA and had no pronounced influence on microbial biomass carbon and bacterial α-diversity, suggesting CPC had a subtle impact on the microbiological environments. Our study provides a theoretical base for the reutilization of fruit wastes and the development of environmental-friendly chelator that assists Cd phytoextraction.

The transmission mode of shoot-associated endophytes in hyperaccumulators and their roles in root microbiome assembly and heavy metal accumulation remain unclear. Using 16S rRNA gene profiling, we investigated the vertical transmission of shoot-associated endophytes in relation to growth and Cd/Zn accumulation of Sedum alfredii(Crassulaceae). Endophytes were transmitted from shoot cuttings to the rhizocompartment of new plants in both sterilized (γ-irradiated) and native soils. Vertical transmission was far more efficient in the sterile soil, and the transmitted endophytes have become a dominant component of the newly established root-associated microbiome. Based on 16S rRNA genes, the vertically transmitted taxa were identified as the families of Streptomycetaceae, Nocardioidaceae, Pseudonocardiaceae, and Rhizobiaceae. Abundances of Streptomycetaceae, Nocardioidaceae, and Pseudonocardiaceae were strongly correlated with increased shoot biomass and total Cd/Zn accumulation. Inoculation of S. alfrediiwith the synthetic bacterial community sharing the same phylogenetic relatedness with the vertically transmitted endophytes resulted in significant improvements in plant biomass, root morphology, and Cd/Zn accumulation. Our results demonstrate that successful vertical transmission of endophytes from shoots of S. alfrediito its rhizocompartments is possible, particularly in soils with attenuated microbiomes. Furthermore, the endophyte-derived microbiome plays an important role in metal hyperaccumulation.

•Two novel geometry shapes for floating or raft-type WEC have been assessed.•WECs in this work are suitable for the sea state of China's Yellow and Bohai Seas.•Capsule-shaped WEC has the best motion performance and the highest response power.•Boat-like WEC has a remarkable energy capturing performance and less mass.

Sintered Ti–6Al–4V compacts prepared from TiH2/60Al40V powder blends were subjected to hot rolling and heat treatment under various conditions. The microstructural evolution and mechanical properties were investigated by X-ray diffraction, scanning electron microscopy, optical microscopy, electron backscatter diffraction, transmission electron microscopy, and universal testing. The hot-rolled Ti–6Al–4V samples with 88% deformation possessed a near-dense lamellar microstructure with ultrafine α lamellae (less than 1 μm). Systematic investigation of the heat treatment temperature and isothermal holding time enabled the evolution of a bimodal microstructure with precipitation of a secondary α phase, ultimately affording an excellent combination of strength and ductility: the yield strength and ultimate tensile strength reached 1248 and 1269 MPa, respectively, with an elongation to fracture of 16.05%.