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Identifying Helicobacter pylori (H. pylori, Hp) infection in animals before and after artificial infection influences the subsequent experiment. We established effective and noninvasive detection methods, including the gastric fluid nested polymerase chain reaction (PCR) method and the 13C-urea breath test, which can detect Hp before modeling Hp infection in Mongolian gerbils. We designed a gas collection equipment for gerbils. Hp nested PCR was also performed on gastric fluid, gastric mucosa, duodenal contents, and faeces of gerbils challenged with Hp. Conventional Hp detection methods, including rapid urease assay and immunohistochemistry, were compared. Moreover, we assessed the natural infection of Hp in 135 gerbils that had never been exposed to Hp artificially from the major laboratory gerbil groups in China. In 10 Hp infected gerbils, the positive detection results were 100%, 100%, 90%, and 10% in gastric fluid, gastric mucosa, duodenal contents, and faeces with nested PCR, respectively. A rapid urease test performed on gastric mucosa showed that all animals were infected with Hp. Immunohistochemical detection and bacteria culture of gastric mucosa samples that were positive by the nested PCR method also confirmed the presence of Hp. 9% (3/35) and 6% (2/31) natural infection rates were found in conventional gerbil groups from the Capital Medical University and Zhejiang Laboratory Animal Center. In conclusion, we established two noninvasive Hp detection methods that can be performed before modelingHp infection, including the gastric fluid nested PCR method and the 13C-urea breath test. [ABSTRACT FROM AUTHOR]

The effects of solution heat treatment and aging on the microstructural evolution and mechanical behavior of a squeeze-cast (SC) Mg-10Gd-3Y-0.5Zr (GW103K) alloy, processed using various applied pressures (e.g., 0.1, 40, 80 and 160 MPa) were systematically investigated. Our results show that, after solution heat treatment, secondary phases and pressure-induced dislocations are dissolved in the matrix of the squeeze-cast alloys. Moreover, subsequent aging heat treatment leads to an increased age-hardening response relative to that in squeeze-cast GW103K and this trend increases with increasing applied pressure. The room temperature tensile test results show that the yield strength (YS) for the squeeze-cast alloy in the as-cast, the as-T4 heat-treated and the as-T6 heat-treated states increases with increasing applied pressure, from 0.1 to 80 MPa, and remains relatively constant when the applied pressure is increased to 160 MPa, whereas the ultimate tensile strength (UTS) and elongation-to-failure ( E ) increases continuously with increasing applied pressure. The measured increases in YS and UTS (or E ), are discussed in terms of the mechanisms that govern the evolution of microstructure in squeeze-cast GW103K, paying particular attention to gain size and porosity. [ABSTRACT FROM AUTHOR]

A kind of Ti–Mg composite was prepared by infiltrating the biodegradable magnesium melt into the porous titanium (p-Ti) with entangled structure. The microstructure and the mechanical properties of the composites were investigated by using the metallographic technique and the compressive testing method. The novelty in the elastic property was discussed based on the experimental results and the referenced data. It was found that as the Ti volume fractions increased from 37.1% to 53.6%, the compressive plateau stress of the p-Ti/Mg composites increased from 175 MPa to 246 MPa, but the Young's modulus decreased from 47 GPa to 22 GPa. When the magnesium matrix was strengthened by adding 0.5 wt.% Zr, the plateau stress and the Young's modulus of the p-Ti/Mg(Zr) composites were reasonably enhanced. The stiffness of the p-Ti/Mg composites is comparable to that of the cortical bone, suggesting their considerable potentials for the load-bearing orthopedic applications. [ABSTRACT FROM AUTHOR]

The effect of Al additions on grain refinement and mechanical properties of Mg–Sm alloys has been investigated. The addition of 3 wt.% Al led to significant grain refinement of Mg– x Sm ( x = 4, 6 and 8 wt.%) alloys due to the formation of Al 2 Sm particles which acted as active nucleant particles for the Mg matrix. An orientation relationship ( 1 ¯ 1 1 ) Al 2 S m / / ( 0 0 0 2 ) Mg , [ 1 ¯ 2 ¯ 1 ] Al 2 Sm / / [ 1 1 2 ¯ 0 ] Mg , [ 0 1 ¯ 1 ] Al 2 Sm / / [ 0 1 1 ¯ 0 ] Mg was reproducibly observed between α-Mg and Al 2 Sm. Furthermore, the Mg–4Sm alloy refined by Al additions had higher ultimate tensile strength and elongation than that refined by Zr which is considered as the most potent grain refiner for Mg alloys. [ABSTRACT FROM AUTHOR]

Based on the geochemical data obtained from the national project about the prevention and control of soil contamination, this paper explored the properties of soil chemical elements in Huanghuaihai Plain, Shandong Province. The results showed that among the grade-one nutritive elements in soil, organic matter, nitrogen and phosphorus were relatively deficient while potassium was rich. Meanwhile, as the grade-two nutritive elements, calcium oxide and magnesium oxide were relatively short and sulfur's content was abundant. About the other beneficial and trace nutritive elements, iron oxide, manganese, molybdenum and boron were deficient, but the content of chlorine was high, hardly lack. The main barriers to improving land productivity were soil salinization and soil heavy metal contamination. The values of soil integrated fertility index that most of the soil in the study area is middle-lower fertilized. Specifically, the low fertility area and lower fertility area are 6 1604 and 1 244 km2 respectively, occupying about 97.43% and 1.97% of the total area. The moderate fertility soil has an area of 172 km2, occupying about 0.27% of the total area. The higher fertility soil covers an area of 128 km2, while the high fertility area of only 76 km2. This article proposed scientific fertilization, elimination of soil obstacle, remediation of heavy-metal-contaminated soil and other effective measures to improve land productivity according to the basic investigation results, which provides a good technological support for the planning and development of good-quality and high-benefit agriculture. [ABSTRACT FROM AUTHOR]

A novel method named low frequency electro-magnetic stirring assisted near-liquidus squeeze casting (LFEMS-NSC) was developed for preparing Mg-RE alloy castings. The grain refining effect in commercially pure Mg (CP-Mg), peritectic Mg-Zr alloy and eutectic Mg-Gd alloy were comparatively analyzed among conventional gravity cast, squeeze cast and LFEMS-NSC. The results showed that the LFEMS-NSC exhibited effective grain refining efficiency in CP-Mg and Mg-Gd alloys. With changing conventional gravity casting or squeeze casting to LFEMS-NSC, the grain morphologies of CP-Mg were transformed from coarse columnar into fine equiaxed grains. The average grain size of CP-Mg was refined from ~10 mm to ~232 µm, where the grain refinement efficiency was comparable to that of adding Mg-Zr master alloy. The application of LFEMS-NSC to Mg-Zr and Mg-Gd alloy systems also show considerable grain refining effect, and it show different effectiveness when the solute content varies. The grain refinement mechanism of LFEMS-NSC is mainly because of the enhanced survival rate of free chill crystals and enhanced heterogeneous nucleation rate through melt pre-treatment by LFEMS and applied pressures during solidification. [ABSTRACT FROM AUTHOR]

The present paper has reported a comparative study on the influence of environmental temperature on the microstructural evolution and tensile mechanical behaviors between squeeze cast (SC) and gravity cast (GC) Mg-10Gd-3Y-0.5Zr (GW103K) alloys. The results revealed that for both alloys, the operative deformation mechanisms at testing temperatures (25–300 °C) were identified to be 〈10−12〉 extension twinning, 〈10−11〉 compressive twinning and 〈10−13〉 compressive twinning in addition to basal or non-basal slips. The elongation increased monotonically with increasing temperature within the range of 25 °C to 300 °C. However, the ultimate tensile strength (UTS) abnormally increased (for GC alloys) or keep constant (for SC alloys) with increasing the temperature from 25 °C to 250 °C, and decreased with further increasing the testing temperature to 300 °C. Moreover, at all testing temperature, both the UTS and elongation of the squeeze cast material were improved relative to those of the gravity cast alloy. The underlying mechanism for the abnormal increase of strength within certain elevated temperature range was attributed to the insufficient strain hardening at lower temperatures that restrict further plastic deformation and lead to pre-mature fracture, and sufficient plastic deformation and softening at higher temperatures promote plastic deformation. The strengths improvements in squeeze cast GW103K alloy can be mainly ascribed to the preventing or limiting of crack nucleation sites and hindering of crack propagations through the reduction of micropores and increasing the amount of grain boundaries. • UTS and elongation both increased with increasing temperature from 25 to 250 °C. • Squeeze cast GW103K alloy show higher properties than gravity cast alloy. • Squeeze cast alloy induce more twins than gravity cast alloy from 25 °C to 250 °C. • The strengths improvement mechanism in squeeze cast GW103K alloy was discussed. [ABSTRACT FROM AUTHOR]

In this paper, the influence of nanoparticle fraction on Portevin-Le Chatelier effect of ZrB 2 nanoparticle reinforced AA6 xxx composites was investigated and friction stir processing was used to uniformize the distribution of nanoparticles. The results indicated that the population of serrations decreases with increasing the fraction of ZrB 2 particles, with stress-drop serrations dominate the early stages of deformation while the stress-up serrations increase with the strain. The stress distribution complies with bimodal configuration, and 2 peaks become closing with the increasing fraction of nanoparticles. The interval for unconstrained motion of dislocation is responsible for the suppression of Portevin-Le Chatelier effect. The mean interval decreases with increasing the nanoparticles fraction. The inter-twisted dislocations in small intervals continuously dedicate to instant balance of stress-drop serrations, strengthen composites and favor the plastic deformation. • The population of serrations decreases with increasing fraction of ZrB 2 particles. • Stress-drop serrations dominate early deformation but stress-up serrations increase with strain. • The stress distribution complies with bimodal configuration, and 2 peaks become closing. • The interval for unconstrained motion of dislocation suppresses Portevin-Le Chatelier effect. [ABSTRACT FROM AUTHOR]

The proper alloy composition ranges for rheo-forming of Mg-RE alloy was obtained through thermodynamic calculations. The low frequency electromagnetic stirring (LFEMS) process was used to fabricate semisolid slurries of Mg-Gd-Zn series alloys, and the role of solute Gd content and the cooling rate in the LFEMS process were systematically investigated. Both the Gd content and cooling rate show effective influences on the microstructure of the Mg-Gd-Zn alloy semisolid slurries. Fine and spherical primary Mg phase can only be obtained by decreasing the cooling rate to less than 1.4 C°/min and increasing the solute Gd content to no less than 9 wt.%. The formation mechanism of non-dendritic morphology of primary Mg phase in Mg-Gd-Zn alloy was proposed to be the dendrite arm root re-melting induced by curvature undercooling and ripening induced by low cooling rate. [ABSTRACT FROM AUTHOR]

The degradation behavior of the porous titanium with entangled structure filled with biodegradable magnesium (p-Ti/Mg) in Hanks' solution was investigated. It was found that the p-Ti/Mg composite had higher strength than pure magnesium and porous titanium with entangled structure (p-Ti). Although the magnesium in p-Ti/Mg was completely dissolved in Hanks' solution after immersion for 104 h, the rest of the sample still maintained strength of about 86 MPa. Moreover, the produced porousness (due to magnesium-degradation) could provide channels for the ingrowth and transportation of bone cells. However, the high corrosion rate of p-Ti/Mg is still a problem when used as a candidate biomedical material, which needs further improvement. [ABSTRACT FROM AUTHOR]

A kind of graded porous titanium–magnesium (Ti–Mg) composite, i.e., about 1–1.5 mm thick porous Ti layer is wrapped over the internal dense Ti–Mg composite, has been successfully fabricated by infiltration casting and acid etching. The outer porous Ti layer maintains its initial entangled structure, which can be easily adjusted to the ideal porosity and the porous structure. The thickness of the porous layer can be controlled by etching time. When the outer porous layer accounted for 41.6–42.4% of the total volume of the cylindrical sample, the compressive strength and the Young’s modulus of the as-prepared graded porous composite are 110 MPa and 5 GPa, respectively, being comparable to that of natural bone. The outer porous layer provides good osteoconduction ability, and the internal dense Ti–Mg composite contributes to the monolithic strength and stiffness. Such biomechanical properties suggest its potentials for load-bearing bio-applications. [ABSTRACT FROM AUTHOR]

The study investigates the effects and mechanisms of laser melting and ultrasound-assisted laser melting treatments on the microstructure and properties of AZ91D magnesium alloy. The findings indicate that the grain size of the samples subjected to laser melting and ultrasound-assisted laser melting is decreased to 40.89 μm (number fraction) and 54.14 μm (area fraction), and 23.21 μm (number fraction) and 29.56 μm (area fraction), respectively. The decrease in grain size can be ascribed to the rapid melting and solidification of the sample surface caused by the high-energy laser beam. This leads to a notable rise in nucleation rate and the development of smaller grains. The effectiveness of laser melting is further enhanced with the introduction of ultrasound. The average microhardness of the samples subjected to laser melting and ultrasound-assisted laser melting shows a significant improvement. Furthermore, the microhardness distribution of the sample subjected to ultrasound-assisted laser melting exhibits greater uniformity. The wear resistance of the samples subjected to laser melting and ultrasound-assisted laser melting shows a significant improvement, as indicated by the friction coefficients of 0.688 and 0.382, respectively. These values represent only 50.7 % and 28.15 % of the friction coefficient of the untreated samples. The improvement of wear resistance can be attributed to the enhancement and homogenization of the microhardness of the samples. The application of laser melting treatment leads to an enhancement in the corrosion resistance of the sample primarily as a result of microstructure densification. However, the introduction of ultrasound does not lead to further improvement in corrosion resistance, possibly as a result of significant grain refinement, which in turn leads to an increase in high-energy grain boundaries. • The grains of AZ91D are refined by laser melting and ultrasound assistance. • The wear resistance mechanism of laser melting and ultrasound is described. • The corrosion resistance can be improved due to densification of the microstructure. • The effects of laser melting and ultrasonic-assistance on AZ91D are compared. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-temperature pre-ageing combined with pre-stretching enhances the strength–ductility synergy of extruded Al-Cu-Li alloys. • The yield strength and elongation of the Al-3.7Cu-1Li-0.40Mg-0.75Ag alloy increase by 4.4 % and 60.3 %, respectively. • Pre-ageing at 110 °C leads to the formation of a large number of thermodynamically stable GP zones within the matrix. • GP zones regulate dislocation configuration and precipitation behavior, contributing to an improvement in elongation. Balancing strength and ductility proves challenging in high-strength wrought Al-Cu-Li alloys, particularly in extruded rods. The abundance of subgrain structures hinders dislocation movement, inevitably sacrificing the ductility. Herein, an effective strategy for enhancing the strength-ductility synergy in an extruded Al-3.7Cu-1Li-0.40Mg-0.75Ag alloy was reported by developing a novel combinatorial pretreatment (CPT), including pre-ageing after solution treatment, followed by pre-stretching. Subsequently, the CPT alloys undergo artificial ageing at 150 °C. Desirable comprehensive mechanical properties (YS = 668 MPa, UTS = 700 MPa, and EL = 12.5 %) were obtained through pre-ageing at 110 °C before 4 % pre-stretching. Notably, the elongation showed a remarkable improvement of 60.3 % compared to the non-CPT sample, without sacrificing the yield strength. Microstructure analysis indicates that the interactions between the GP zones and dislocations facilitated energy dissipation during pre-stretching, effectively mitigating local stress concentration. Consequently, promoted ductility was realized through a more uniform dislocation distribution. Furthermore, the dense GP zones formed during pre-ageing served as the heterogeneous nucleation sites for precipitates, increasing the volume fraction of θ′ phases. This adjustment in dislocation motion further contributed to ductility improvements. Our approach offers new insights into developing high-performance extruded Al-Cu-Li alloys with both high strength and desirable ductility. [ABSTRACT FROM AUTHOR]

In this work, the in-situ ZrB 2 /AA6111 composites with different particle volume fractions were prepared by direct melt reaction method and followed by hot extrusion deformation and T6 heat treatment. The microstructure characteristics, tensile and fatigue properties were carefully studied. The results showed that the addition of nano-ZrB 2 particles made ZrB 2 /AA6111 composites have finer grains and the ultimate tensile strength of composites increases with the increase of particle volume fraction. The ZrB 2 /AA6111 composites showed higher fatigue limits than the unreinforced alloy, and the composites with a particle volume fraction of 2 vol% have the highest fatigue limit of 125 MPa, which is a 31.5% increase compared to the unreinforced alloy. Through microstructure analysis, it is found that the fatigue limit was related to the volume fraction and distribution of ZrB 2 particles. The initial cracks of composite and unreinforced alloy were both caused by persistent slip bands and the crack propagation of the composites was more complex due to the resistance of reinforcing particles. [ABSTRACT FROM AUTHOR]

The unclear contraction behavior of Mg-Gd-Y-Zr alloy during low-pressure sand casting bring obstructs into the dimensional control in the fabrication of large and complex parts, restricting the further engineering applications of this alloy. This paper investigated the rule for free and constrained contraction of typical Mg-Gd-Y-Zr (Mg-9Gd-3Y-0.5Zr, VW93K) alloy during low-pressure sand casting. A series of castings with different volumes and geometric structures were designed and a 3D scanner was employed to measure different types of dimensions, which were then used for the calculation of contraction coefficients. The convergent value of free contraction coefficients was derived through statistical analysis, and the correlation between constrained contraction coefficients and geometric characteristics of castings was established by the utilizing of core volume factor. In the condition of low-pressure casting, free contraction coefficients of VW93 alloy are concentrated around a fixed value of 1.72%, constrained contraction coefficients of VW93 alloy show a decreasing linear tendency against core volume factor, and pouring pressure makes effects on free contraction. The experimental results and proposed formulas provide guidance for accurate dimensional control in fabrication of large and complex Mg-RE alloy parts by low-pressure sand casting. [ABSTRACT FROM AUTHOR]

Cast Al-Li alloys show attractive potential for application in the field of manufacturing large-size and complex parts as a result of profound weight reduction and good fluidity. However, the ductility and strength of sand-cast Al-Li alloys are relatively poor due to the low cooling rate of sand casting. In this study, Sc and Ti were added to sand-cast Al-Li-Cu-Mg-Zr casting alloy to investigate the microstructure evolution and tailor the final performance for the first time. The results showed that grain decreased from 189 µm to 56 µm and the needle Cu-rich phase increased in the vicinity of grain boundaries as the total element content of Sc and Ti increased. After aging at 175 °C, the enrichment of the T 1 and S′ phases, the finer δ′, the higher number density of core-shell composites, and the narrowed δ′-precipitation free zones (δ′-PFZs) were stimulated by Sc and Ti, leading to a significant increase in strength of the peak-aged alloy. The SZT alloy exhibits the best yield strength of 359 MPa and ultimate tensile strength of 452 MPa with an adequate elongation of 4.6 %. In addition, a Li-rich zone was observed and intersected with T 1 phase, which provided a new precipitation path for Li atom diffusion and nucleation of T 1 precipitates. The present study suggests that microalloying with Sc and Ti is expected to be an effective strategy to simultaneously improve the strength and ductility of sand-cast Al-Li alloys. • The effect of Sc and Ti on the microstructure evolution of strengthening phases is analyzed. • A good combination of strength and elongation is obtained by the combined addition of Sc and Ti. • The contributions from different strengthening mechanisms for peak-aged Al-Li-Cu-Mg-Zr alloy were studied in detail. [ABSTRACT FROM AUTHOR]

Abstract The microstructures and mechanical properties of cast and extruded Al-4Cu-1Li-0.4Mg-0.1Zr- x Zn alloys were investigated and the amount of Zn additions was up to 1.1 wt%. The results showed that Zn addition could bring additional MgZn 2 phases at the grain boundary and slightly refine the grain size in the as-cast alloy. The mechanical properties of extruded Al-4Cu-1Li-0.4Mg-0.1Zr -x Zn alloy increased gradually with the Zn content under different conditions. The yield strength (YS) and ultimate tensile strength (UTS) of T8 treated (stretched by 4% and aged at 150 °C for 32 h) 1.1 Zn alloy could reach 639 MPa and 666 MPa, while elongation (EL) remained at 10.9%. For alloys peak-aged at 175 °C for 32 h (T6 treated), Zn could effectively promote the precipitation of T 1 phases (Al 2 CuLi) but decrease the volume fraction of θ′ phases (Al 2 Cu) in the matrix. The coarsening of T 1 phases could be obviously suppressed by the addition of Zn under overaged condition. However, the precipitate of T 1 phases promoted by Zn under the T8 condition is not as obvious as the T6 condition. [ABSTRACT FROM AUTHOR]

As a kind of cast aluminum alloy with high strength, Al–Li–Cu–Mg series alloys exhibit desirable stiffness and formability, while a limited investigation has discussed the influence of cooling rate on microstructure and mechanical properties of these alloys. In this work, the effect of cooling rate during casting on microstructure evolution and mechanical properties of cast Al–2Li–2Cu-0.5Mg-0.15Sc-0.1Zr-0.1Ti alloy was investigated using a step-like iron mold. The results showed that the increased cooling rate refined the grain size and augmented the volume fraction of second phase in the as-cast microstructure. In the aging process, the rapid cooling rate markedly promotes precipitation and suppresses coarsening of the δˊ(Al 3 Li), T 1 (Al 2 CuLi) and Sˊ(Al 2 CuMg) phases, which plays a vital role in enhancing strength of the peak-aged alloy. In addition to diffusion and vacancy mechanisms, a Li-rich zone offers a new precipitation pathway for T 1 precipitates. Notably, the rapid cooling rate of 16.1 °C/s significantly facilitated the formation and inhomogeneous distribution of the cubic σ(Al 6 Cu 5 Mg 2) phase, which competed with the T 1 and Sˊ phases for Cu and Mg atoms. Finally, the formation mechanism of the σ phase under different cooling rates was discussed, and the strengthening and fracture mechanisms were quantified. The present work is expected to enlighten the understanding of the microstructure evolution of Al–Li alloys with varied cast cooling rates. [ABSTRACT FROM AUTHOR]

In third-generation Al–Cu–Li alloys, T 1 , S', and θ' precipitates are the primary strengthening phases, and the strength-ductility synergy of the alloys depends strongly on their precipitation behavior. This study aimed to regulate the precipitation behavior among these precipitates by optimizing Ag/Mg ratio in Al–Cu–Li alloys, and its influence on mechanical properties and fracture mechanism was investigated. To this end, four alloys were designed with a total content of 1.1 wt% of Ag and Mg, and an Ag/Mg ratio ranging from 0.24 to 5.63. The results shows that an increase in the Ag/Mg ratio dramatically accelerated the ageing process and shortened the peak-ageing time. At 150 °C, the precipitation sequence of alloys with an Ag/Mg ratio below 0.95 was SSS→GPB zone +δ′/β'→S'+T 1 , which transformed into SSS→GP zone +δ′/β'→θ'+T 1 when the Ag/Mg ratio was above 1.87. The T 1 , S', and θ' precipitates coexisted and were dispersedly distributed among studied alloys with an Ag/Mg ratio ranging from 0.95 to 1.87. An Ag/Mg ratio of 1.87 resulted in the fastest ageing hardening response and the highest strength (YS = 705 MPa, UTS = 717 MPa) because of the highest volume fraction of T 1 precipitates. Moreover, the fracture mode changed from transgranular fracture to intergranular fracture with increasing Ag/Mg ratio due to the difference in distribution and number density of these precipitates between the matrix and grain boundary. [ABSTRACT FROM AUTHOR]

The Mg-8Gd-4Y–1Zn–Mn (wt%) alloys prepared by semi-continuous casting and homogenizing treatment were extruded using different extrusion ratios and subsequent cooling processes. The microstructure, texture and mechanical properties of extruded alloys were investigated. The dynamic recrystallization process is promoted by increasing the extrusion ratio, while the static recrystallization process is suppressed by subsequent water cooling rather than air cooling. When the recrystallization ratio is relatively low, the non-recrystallized region showing a fiber < 10 1 ‾ 0 > Mg //extrusion direction (ED) texture component dominates the texture characteristic. With the increase of the recrystallization ratio, the recrystallized region exhibiting an abnormal <0001> Mg //ED texture gradually dominates the texture characteristic. The grain boundary energy anisotropy and the grain boundary mobility anisotropy are assumed to be changed by the Gd and Y addition, which affect the preferential growth of the abnormal <0001> Mg //ED oriented grains and eventually lead to the formation of abnormal texture component. The as-aged alloy extruded at the extrusion ratio of 6 followed by air cooling shows the highest strength. The extruded alloys with an intensive abnormal texture component exhibit the best mechanical isotropy in both as-extruded and as-aged conditions. The differences in strength along different directions are mainly resulted from the fiber strengthening. [ABSTRACT FROM AUTHOR]