Average Grain Research Articles

Advanced Tuning of electric and dielectric properties in Ba0·5Ni0.5-xCdxFe2O4 spinel ferrites for high-frequency devices with barium dopants

Spinel ferrites are vital in developing next-generation technologies with potential applications covering the medical, electronic, and material industries. Nickel-cadmium spinel ferrites are soft magnetic materials having lots of applications ranging from electronics and magnetic to sensors industries. Herein, we developed cadmium-substituted spinel ferrites (Ba0·5Ni0.5-xCdxFe2O4) and their nanocomposite with polymer polyvinyl alcohol (PVA). The results evidently indicate that the successfully developed Ba0·5Ni0.5-xCdxFe2O4, which also confirmed the loading of PVA onto the Ba0·5Ni0.5-xCdxFe2O4 materials. XRD results confirmed orthorhombic single-phase structure. The optimal particle size was 27.22 nm, and the minimum was 21.25 nm, respectively, as shown by Ba0·5Ni0·1Cd0·4Fe2O4 (x = 0.4) and PVA composite of Ba0·5Ni0·2Cd0·3Fe2O4 (x = 0.3). It was also observed that the composites showed lower particle size than nano-ferrites. Spectral analysis (Fourier Transform Infrared Spectroscopy) confirmed the formation of spinel ferrites by detecting the M − O bonds in the 400-800 cm−1 region. υ1 and υ2 were appeared in the range 560–609 cm−1 and 439-466 cm−1, corresponding to M-O. The average grain size of spinel ferrites was 0.55, 0.50, 1.03, and 1.31 μm for Ba0·5Ni0.5-xCdxFe2O4 (x = 0.1, 0.2, 0.3, and 0.4) spinel ferrites. Dielectric parameters revealed that these materials are suitable for high-frequency devices due to their low dielectric loss, high quality factor, short relaxation time, and diverse responses.

Effects of rolling process and microstructure on the brittle crack initiation and arrest of a marine steel under low‐temperature

AbstractThe effects of the rolling process and microstructure on the brittle crack initiation and arrest of marine steel were systematically investigated. The microstructures of two steel plates produced by different rolling processes were observed and analyzed. The results demonstrated that the rolling process significantly influenced the microstructure. As the rolling temperature decreased, the grain size decreased, the high‐angle grain boundary (HAGB) content increased, and the average grain misorientation angle increased. The brittle crack initiation and the arrest abilities were evaluated by initiation fracture toughness and crack arrest toughness, respectively. The initiation fracture toughness and crack arrest toughness increased with the decreasing grain size and the increasing content of HAGBs. Finally, the influence of microstructure on the brittle crack initiation and arrest ability was explained from two aspects: (1) the critical event of crack initiation at low temperatures, and (2) the hindering effect of HAGB on the propagation of brittle cracks.

Fatigue Behavior of Medium Entropy Alloys AlCrFe<sub>2</sub>Ni<sub>2</sub> and AlCrFe<sub>2</sub>Ni<sub>2</sub>Mo<sub>0.1 </sub>- A Comparison with Super Duplex Steel 1.4517

In the present study the notched fatigue behavior of two multi-phase medium entropy alloys (MEAs) AlCrFe2Ni2 and AlCrFe2Ni2Mo0.1 was characterized by three-point-bending (3-PB), along with a super-duplex steel 1.4517 as a reference material. An analytical approach for characterizing the fatigue notch factor (kf), based on grain size analysis in combination with finite element modelling (FEM) was used, relating the theory of critical distances (TCD) to the grain size of the material. To validate the approach, for the reference steel, the fatigue notch factor was also determined experimentally by comparing the fatigue behavior of notched and smooth specimens, resulting in an experimentally determined fatigue notch factor (kf) ~ 1.07. The numerically and analytically estimated notch effects increase with decreasing average grain size and vary between ~ 1.07 for the coarse-grained reference material – in very good agreement with the experimental results – and ~ 1.35 for the much more fine-grained AlCrFe2Ni2Mo0.1 medium entropy alloy. Note that these values are significantly lower than the stress concentration factor (kt) ~ 1.58, associated with the notch geometry. Fatigue endurance limits were measured at a fatigue stress ratio R ~ 0.1 (unidirectional stress), but were converted to fatigue amplitudes at R = -1 (σa, R-1, fully reversed stress), to be able to make due comparisons with available literature data, by using the elliptical relationship. The resulting fatigue endurance limit amplitudes for specimens surviving at least 2E+06 cycles for a minimum of three tested samples and including notch effects are σa, R-1 ~ 508 MPa for the AlCrFe2Ni2 alloy, σa, R-1 ~ 540 MPa for the AlCrFe2Ni2Mo0.1 alloy modification and σa, R-1 ~ 400 MPa for the reference super-duplex steel, putting the analyzed MEAs into a very competitive position compared to Cobalt containing multi-phase high or medium entropy alloys as well as commercially available steels.

Nanoscale oxide and γ' phase synergistically strengthened nickel-based alloys with varying Al/Ti ratios produced by HIP

In this paper, three nickel-based superalloys with different Al/Ti atomic ratios (1, 1.8 and 16), designated as ODS-1, ODS-1.8 and ODS-16, respectively, were prepared by mechanical alloying (MA) followed by hot isostatic pressing (HIP). The evolution of microstructure and tensile properties of the alloys under varying Al/Ti ratio was analyzed and discussed. The result showed that the size, type and constitution of oxides change with variation of Al/Ti ratio. The average size of the oxides decreases with increasing Al/Ti ratio, which is 15.8 nm for ODS-1, 13.8 nm for ODS-1.8 and 11.8 nm for ODS-16, respectively. The oxides in ODS-1 contain 21.4% Y4Zr3O12, 42.9% Y2TiO5, 21.4% YAM and 14.3% YAP. The oxides in ODS-1.8 consist of 23.5% Y4Zr3O12, 35.3% Y2TiO5, 17.6% YAM and 23.5% YAP. In contrast, only two types of oxides are formed in ODS-16, including 50% Y4Zr3O12 and 50% YAP. As the Al/Ti ratio is increased from 1 to 16, the percentage of Y-Al-O phase increases from 35.7% to 50%, while the proportion of Y-Ti-O phase decreases from 42.9% to 0%. Increasing Al/Ti ratio inhibits the formation of Y-Ti-O phase while promoting the generation of Y-Al-O particles. The finer oxide distribution in ODS-16 is considered to be the main reason for its finer grain size distribution. The bimodal distribution of the γ' phase can be found in all three alloys, but the bimodal distribution feature of the γ' phase in ODS-1 and ODS-1.8 is more significant than that in ODS-16. The average grain size decreases with increasing Al/Ti ratio. The tensile strength at 700 °C is reduced, but the ductility is improved with the increase of Al/Ti ratio. The influence of Al/Ti ratio on the formation of nanoscale oxides and γ' phases are revealed.

Effect of Nb content variations on the microstructure and mechanical properties of NiCrMo welded joints

The effects of varying the Nb content (1.04 wt%-1.55 wt%) in NiCrMo weld metals on the microstructure, tensile strength and cryogenic impact toughness were investigated. The microstructure of the three different weld metals was observed to be composed of austenite matrix and precipitates by characterization techniques such as SEM, EDS, EBSD, and TEM. The precipitates within the grains were NbC and Ni3Nb phases, and the precipitates on the grain boundaries were NbC phases. With the increase of Nb content, the average grain size of austenite decreased from 205.3 μm to 161.4 μm, and the area fraction of precipitates increased from 1.41% to 3.97%. The cryogenic impact value of the welded joints decreased from 97 J to 76.3 J, while the tensile strength increased from 682.5 MPa to 710 MPa, indicating that the increase in the area fraction of the Nb-rich phase had a deleterious effect on the cryogenic impact toughness and was conducive to the elevation of the tensile strength. When the Nb content in the weld metal was 1.25 wt%, the comprehensive mechanical properties of NiCrMo welded joints were the best, with a tensile strength of 695.5 MPa and a cryogenic impact value of 86.7 J.

Microstructure and corrosion behavior of A390-10 wt% SiC composite-AA2024-T6 aluminum alloy dissimilar joint: Effect of post-weld heat treatment

The weldability of aluminum matrix composites to other materials, such as aluminum alloys, is an essential point in expanding the use of these materials. This study investigated the effect of rotational speed and post-weld heat treatment on the microstructure, mechanical properties, and corrosion behavior of A390-10 wt% SiC composite/AA2024-T6 aluminum alloy dissimilar joint. Friction stir welding is performed using a square frustum pyramid pin tool with a rotational speed of 400–1200 rpm and a traverse speed of 40 mm/min. Results found that a surface groove formed on the weld crown at a rotational speed lower than 800 rpm due to insufficient material flow. Also, the tunnel defect formed on the advancing side at a rotational speed higher than 1000 rpm due to the turbulent flow of material. By increasing rotational speed from 800 to 1200 rpm, the average grain size of the advancing and retreating sides increased by 41.1 and 46.3 %, respectively. Compared to AA2024-T6 and A390-10 wt% SiC composite base metals, the average hardness of the stir zone of the joint fabricated by the rotational speed of 800 rpm increased by 8.4 and 38.2 %, respectively. By increasing the rotation speed from 800 to 1000 rpm, the yield strength and ultimate tensile strength decreased by 6.8 and 6.5 %, respectively. By decreasing rotational speed from 1000 to 800 rpm, the elongation and corrosion resistance decreased by 5.4 % and 34.7 %, respectively. After post-weld heat treatment, the hardness, yield strength, ultimate tensile strength, and corrosion resistance increase 15.9, 12.7, 7.8, and 28.9 %, respectively.

Utilization of Rhodopseudomonas palustris in Crop Rotation Practice Boosts Rice Productivity and Soil Nutrient Dynamics

Using beneficial microorganisms, such as purple non-sulfur bacteria (PNSB), has shown enormous potential for improving plant growth and agricultural production. However, the full extent of their benefits and interactions with agricultural practices is yet to be fully understood. The present study aimed to investigate the use of PNSB in crop rotation practice, focusing on its impact on rice growth and yield. The experiment was conducted over two rice cropping seasons, with djulis grown between the rice as a rotation crop. The study shows that PNSB treatment increased the concentration of 5-aminolevulinic acid (5-ALA) in plants, indicating enhanced photosynthesis. Moreover, when combined with crop rotation, PNSB remarkably improved soil fertility. These combined benefits resulted in substantial increases in tiller numbers (163%), leaf chlorophyll content (13%), and lodging resistance (66%), compared to the untreated plants. The combined treatment also resulted in higher productive tillers per hill (112%), average grain per hill (65%), and grain fertility (26%). This led to increased grain yield (65%), shoot dry weight (15%), and harvest index (37%). The findings clearly suggest that the incorporation of PNSB in crop rotation strategies can significantly augment the growth and yield of rice crops. These insights, pivotal for sustainable rice cultivation, hold the potential to simultaneously tackle the pressing issues of global food security and climate change.

Stable and wide temperature range superelasticity in an Mo-doped nanocrystalline Ni–Ti–Mo shape memory alloy

The phase transformation and superelastic behavior of nanocrystalline Ni48Ti50Mo2 alloy wires were investigated. Nanocrystalline (NC) alloys were obtained via severe plastic deformation of cold-drawing followed by annealing at low temperatures. The results indicate that the NC Ni48Ti50Mo2 undergoes a single-step B2→R phase transformation and a two-step B2→R→B19′ phase transformation in coarse crystals (CG). The NC alloy wire exhibits 8 % recoverable strain under a tensile stress of 1.1 Ga and superelasticity exists in a wide temperature range from −60 °C to 100 °C. After 50 cycles of tension fatigue testing, the superelastic upper plateau stress reduction rate is 7 % with almost no residual strain accumulation, which has excellent superelastic stability compared with fine crystals and coarse crystals. Transmission electron microscope (TEM) reveals an average grain size of 20 nm. The stable superelasticity is attributed to the nanocrystalline reinforced matrix, which hinders dislocation generation and slip.

Enhancing the corrosion resistance of high Mo S31254 super austenitic stainless steel using grain boundary engineering

Super austenitic stainless steel (SASSs) with a high Mo content exhibit excellent resistance to intergranular corrosion (IGC), Its mechanical properties mainly depend on solid solution strengthening. Meanwhile, grain boundary engineering (GBE) can simultaneously improve the corrosion resistance and mechanical properties of Mo-rich austenitic stainless steel using the resistance to IGC of Mo. However, recrystallization annealing is extremely difficult due to the sensitive precipitation of Cr-rich and Mo-rich precipitations in SASSs. Therefore, this study explores the effect of large deformation, high temperature, and short-time annealing on the corrosion resistance of SASSs. The results show that a recrystallized organization with an average grain size of 13.3 μm was prepared by 50% cold rolling deformation and 2 min high-temperature short-time annealing at 1150 °C. The highest percentage of Σ3 GBs is about 34%, the percentage of other low-energy GBs is relatively low (only about 6%), and the rest are random high-angle grain boundaries (RHAGBs), which account for about 60%. It can be seen the corrosion resistance of random GBs after GBE treatment is superior to that of solution treatment. Meanwhile, medium-temperature aging improved the resistance to IGC of SASSs, especially after aging at 450 ℃, a small amount of Mo is enriched along the GBs, which promotes the formation of Cr2O3 and Mo-rich oxides in the passivation film and improves the corrosion resistance. The above results provide guidance for improving the corrosion resistance of Mo-rich austenitic stainless steels.

Effect of Electrolytic Plasma Polishing on Surface Properties of Titanium Alloy

Electrolytic plasma polishing (EPPo) is an advanced metal surface finishing technology with high quality and environmental protection that has broad application prospects in the biomedical field. However, the effect of EPPo on surface properties such as corrosion resistance and the wettability of biomedical titanium alloys remains to be investigated. This paper investigated the changes in surface roughness, surface morphology, microstructure, and chemical composition of Ti6Al4V alloy by EPPo and their effects on surface corrosion resistance, wettability, and residual stress. The results showed that Ra decreased from 0.3899 to 0.0577 μm after EPPo. The surface crystallinity was improved, and the average grain size increased from 251 nm to more than 800 nm. The oxidation behavior of EPPo leads to an increase in surface oxygen content and the formation of TiO2 and Al2O3 oxide layers. EPPo can significantly improve the corrosion resistance and wettability of titanium alloy in simulated body fluid and eliminate the residual stress on the sample surface. The surface properties are enhanced not only by the reduction in surface roughness but also by the formation of a denser oxide film on the surface, changes in the microstructure, an increase in surface free energy, and the annealing effect developed during EPPo. This study can provide guidance and references for applying EPPo to biomedical titanium alloy parts.

Effects of HiPIMS Duty Cycle on Plasma Discharge and the Properties of Cu Film.

In this paper, Cu thin films were deposited on Si (100) substrates by the high-power impulse magnetron sputtering (HiIPMS) technique, and the effects of different duty cycles (from 2.25% to 5.25%) on the plasma discharge characteristics, microstructure, and electrical properties of Cu thin films were investigated. The results of the target current test show that the peak target current remains stable under 2.25% and 3% duty cycle conditions. Under the conditions of a 4.5% and 5.25% duty cycle, the target peak current shows a decreasing trend. The average power of the target shows a rising trend with the increase in the duty cycle, while the peak power of the target shows a decreasing trend with the increase in the duty cycle. The results of OES show that with the increase in the duty cycle, the total peak intensity of copper and argon emissions shows an overall increasing trend. The duty cycle from 3% to 4.5% change in copper and argon emission peak total intensity change is not obvious. The deposition rate and surface morphology of the copper film were investigated by scanning electron microscopy, and the deposition rate of the copper film increased with the increase in the duty cycle, which was mainly due to the increase in the average power. The surface roughness of the copper film was evaluated by atomic force microscopy. X-ray diffraction (XRD) was used to analyze the grain size and texture of the Cu film, and the results showed that the average grain size of the Cu film increased from 38 nm to 59 nm on the (111) and (200) crystal planes. Four-probe square resistance test copper film resistivity in 2.25%, 3% low duty cycle conditions of the copper film resistivity is generally higher than 4.5%, 5.25% high duty cycle conditions, the copper film resistivity shows the trend of change is mainly affected by the copper film grain size and the (111) face of the double effect of the optimal orientation. The lowest resistivity of the copper film measured under the 4.5% duty cycle condition is 1.7005 μΩ·cm, which is close to the intrinsic resistivity of the copper film of 1.67 μΩ·cm.

Enhanced Magnetic and Dielectric Properties of YFeO3 Ceramics via Formation of Solid‐Solution with Sr2Bi4Ti5O18 and ZnSnO3 Oxides

In the present investigation, magnetic and dielectric properties of solid‐solution formed between the YFeO3 with the similar crystal structure of other oxide materials are focused on. Orthorhombic crystal structure of YFeO3 (YFO), Sr2Bi4Ti5O18 (SBT), and ZnSnO3 (ZS) nanomaterials are considered to prepare the solid solutions at 1150 °C/3 h. YFO and solid solutions exhibit the orthorhombic crystal structure, which is conformed through Rietveld refinement using X‐Ray powder diffraction pattern. The decreased average grain size is observed for the solid solution (3.0 μm for YFO and ZS and 2.6 μm for YFO and SBT) when compared to YFO (3.4 μm) through scanning electron microscopy. Oxidation state of each atom/ion/element present in the YFO and solid solutions are conformed through X‐Ray photoelectron spectroscopy studies. The solid solution formed between the YFO and SBT exhibits high magnetization value (2.92 emu g−1) and high coercive filed (67.5 Oe) when compared to solid solution formed between the YFO and ZS (magnetization value = 2.48 emu g−1, and coercive filed = 46.4 Oe) and YFO (magnetization value = 1.91 emu g−1, and coercive filed = 61.8 Oe). High dielectric permittivity (εr), low dielectric loss (tan δ), and low conductivity are observed for the solid solution formed between the YFO and SBT, when compared to other materials in this study.

Development of rare-earth free Mg–Si–Zn–Cu alloy with outstanding mechanical properties and high thermal conductivity

Development of magnesium alloys with exceptional mechanical properties and high thermal conductivity is a prominent subject in the field of thermal conductive magnesium alloys. Rare-earth containing magnesium alloys are known for their ability to achieve higher strength. However, they often exhibit higher density and higher cost. This study developed a high-strength and high-conductivity magnesium alloy without the need for rare earth elements through considered composition design. By utilizing the pinning effect of Mg2Si and solute drag effects of Zn and Cu, a fine-grained magnesium alloy with an average grain size of merely 4.5 μm was achieved. The simultaneous introduction of hard Mg2Si particles and ductile Cu-rich particles allow Mg-1.38Si-0.5Zn-0.5Cu alloy (SZC100) to attain a desirable combination of strength and plasticity. Althogh free of rare-earth elements, this magnesium alloy demonstrates a thermal conductivity of 141.5 W/(m·K), a yield strength of 238 MPa, and an elongation of 16.2 %.

Microstructure Evolution and Homogenization Kinetics of 15Cr–30Ni–Fe Heat‐Resistant Alloy

The as‐cast microstructure, microsegregation of alloying elements, and microstructure evolution during homogenization of the newly designed 15Cr–30Ni–Fe heat‐resistant alloy are studied. Ti, Nb, Si, and Mo segregate at the interdendritic region. The brittle eutectic Laves phase contains Fe, Ti, Ni, Nb, Si, and Mo, which is identified as the Fe2Ti Laves phase. The activation energy for the Fe2Ti Laves phase dissolution is close to the activation energy for Ti diffusion in the γ matrix based on the Johnson–Mehl–Avrami–Kolmogorov analysis. The back‐diffusion of Ti to the γ matrix is the limiting step for the dissolution of Fe2Ti Laves phase. The kinetic equation of homogenization considering lattice parameters and pre‐exponential factor correction is established. After the double‐stage homogenization at 980 °C/10 h + 1140 °C/4 h, the volume fraction of the Laves phase decreases from 5.11% to 0.26%, and the large eutectic Laves phase is completely dissolved. The reduction in the standard deviation of microhardness at different soaking times effectively reflects the gradual decrease in the degree of microsegregation of alloying elements. The average grain size of the alloy after homogenization is 410 ± 63.1 μm, which is beneficial to control the further refinement of grain during the subsequent hot working.

Ultrasonic-assisted alkali hydrolysis of polyethylene terephthalate fabric and its effect on the microstructure and dyeing properties of fibers

Abstract In this study, ultrasound energy was applied to assist the alkali hydrolysis of polyethylene terephthalate (PET) fabric, and then, the results were compared with those of the mechanical oscillating method, which was used as the control. The effects of various factors such as the sodium hydroxide concentration, the dosage of dodecyl dimethyl benzyl ammonium chloride (DDBAC), and the frequency on the weight loss of the PET fabrics were systematically investigated. The surface appearance and microstructures of the treated fibers with different methods were analyzed using a scanning electron microscope and X-ray diffraction, respectively. The results showed that DDBAC played a prominent accelerating role in the hydrolysis of the PET polymer, and the frequency had a great influence on the weight loss of the PET fabric. Ultrasound with a frequency of 60 kHz showed a similar decomposition rate as the control, resulting in similar weight loss, which was the highest value among the three frequencies (20, 60, and 80 kHz). In addition, the application of ultrasonic energy led to more pits on the fiber surface, a smaller average grain size, and decreased crystallinity of the treated fibers, while the mechanical oscillating method resulted in slightly increased crystallinity. By comparing the K/S value of the dyed fabrics with two commercial disperse dyes, we found that the treatment method had no obvious correlation with the color depth of the treated fabric.

Investigation of the influence of defect volume on weld strength during FSW: A simulation and experimental study

Internal defects such as voids/cavities significantly hamper the weld quality, resulting in lower weld efficiency and mechanical properties. Therefore, there is a scope for developing a relationship between quantum of defects and weld efficiency. This research uses a thermomechanical model based on coupled Eulerian-Lagrangian (CEL) to predict defect formation during friction stir welding (FSW) of a 3 mm thick AA2024. A square pin tool is used in current research. A novel concept of defect volume is developed using the Eulerian volume fraction within the weld domain, and a mathematical equation is developed to calculate weld efficiency as a function of defect volume, stir zone temperature, and axial force. The developed model predicted weld efficiency with less than 5 % error with R-squared coefficients of 0.9. The model established effective material flow behavior having an intercalated zig-zag path, resulting in defect-free weld with 86 % weld efficiency at 1500 rpm and 150 mm/min. It has a defect volume of 0.45 mm3. EBSD analysis shows an average grain size of 4.9 and 6.1 µm for defect-free and defective welds, respectively. Material flow, mechanical, and metallurgical characterization of lowest and highest weld efficiency is carried out to understand the underlying weld failure mechanism.

Annealing temperature effects on microstructure and magnetic properties of Fe-6.5wt. %Si alloy strips prepared by TSTRC process

The Fe-6.5wt.%Si alloy exhibits remarkable soft magnetic characteristics, such as high magnetic permeability, low coercivity, high resistivity, and nearly zero magnetostriction. These attributes establish it as an ideal material for low-power, low-noise electric motors and transformers. This investigation aimed to assess the impact of annealing temperature (ranging from 800 to 1200 °C for 1 h) on the microstructure, texture, and magnetic properties of a 0.15 mm thick Fe-6.5wt.%Si alloy sheet, which was obtained by subjecting the strips produced through the top side-pouring twin-roll casting (TSTRC) process to multi-pass warm rolling in the temperature range of 600 ∼ 800 °C, avoiding hot rolling. Additionally, the recrystallization mechanism of the annealed sheet at 1100 °C for 1 h was explored. The findings indicate that enhancing the annealing temperature corresponded to a reduction in magnetic induction (B8 and B50) as well as iron losses (P10/50, P10/400, and P2/1000). The annealed sheet at 1200 °C for 1 h demonstrated the most favorable magnetic properties, displaying iron losses of 0.486 W/kg, 6.895 W/kg, and 1.232 W/kg for P10/50, P10/400, and P2/1000, respectively. These results illustrate excellent overall magnetic characteristics. The coercivity (Hc) of both B8 and B50 decreased as the annealing temperature increased in the hysteresis loop measurements. Specifically, for B8, it decreased from 62.84 A/m to 24.50 A/m, and for B50, it decreased from 78.10 A/m to 35.50 A/m. The average grain size of the samples gradually increased as the annealing temperature ranged from 800 to 1200 °C. The dominant texture observed was {111}, and the volume fraction of {111} texture increased while the volume fractions of {100} and {110} textures decreased. Upon annealing at 1100 °C for 8 s, the elongated and flattened deformed structures were mainly replaced by equiaxed grains, indicating the completion of the recrystallization process. However, there was a noticeable distinction in the coarsening degree of equiaxed grains based on their orientations. The presence of λ-oriented grains was less prominent, while α-oriented and γ-oriented grains were relatively more abundant. As the annealing time increased from 8 s to 1 h, there was a decrease in the presence of λ-oriented and α-oriented grains, while the presence of γ-oriented grains significantly increased.

Microstructure and mechanical properties of Ti modified 7075 aluminum alloy fabricated by selective laser melting

In this study, Ti/7075 aluminum alloy samples were successfully prepared by selective laser melting (SLM). The effects of process parameters and solution treatment on the microstructure and mechanical properties were studied. Research shows that when the laser power is 270 W, the scanning speed is 600 mm/s, and the laser energy density is 166.67 J/mm3, the density of the Ti-added composite powder sample increases from 96.63% to 97.30% compared to the 7075 sample. Ti reacts in situ to generate the Al3Ti phase during the SLM process. Al3Ti has a heterogeneous nucleation effect, which can promote the transformation of columnar crystals into equiaxed crystals and inhibit the occurrence of anisotropy and hot cracks to a certain extent. The average grain size of the sample was refined from 18.71 μm to 2.24 μm. Under the optimal process parameters, the room temperature tensile strength of the as-deposited Ti/7075 aluminum alloy is 358 MPa, and the elongation is 15.5%. After solution treatment, the performance is further improved, the tensile strength is increased to 442 MPa, and the elongation is increased to 20.1%.

Microstructure evolution and ductility improvement of additively manufactured biodegradable zinc–magnesium alloys via annealing

Zinc–magnesium (Zn–Mg) alloys, fabricated by laser powder bed fusion (LPBF) additive manufacturing techniques, have emerged as promising candidates for biomedical implants due to their biodegradation capability, superior mechanical strength, and excellent biocompatibility. However, LPBF-fabricated Zn–Mg alloys still face challenges related to extremely low ductility and limited exploration of degradation characteristics. In this study, the impact of Mg incorporation on the printability, degradation properties, microstructure, and mechanical properties of LPBF-fabricated Zn–Mg alloys was primarily investigated. Furthermore, we proposed a viable annealing post-processing route for the first time to tailor the microstructural characteristics of the fabricated Zn–Mg alloy and enhanced its limited ductility. The results demonstrated that by applying a laser power of 80 W and a scanning speed of 600 mm/s, the relative density of LPBF-fabricated Zn–Mg alloy reached 98.62%. Increasing the Mg amount from 1 to 5 wt% refined the grain size while promoting an increase in Mg2Zn11 and MgZn2 phases. Among these compositions, the Zn–1Mg alloy exhibited the greatest degradation rate at 0.126 mm/year. The annealing treatment facilitated the microstructure evolution of the Zn–1Mg alloy, resulting in equiaxed grains, increased average grain size, high-angle grain boundaries, and enrichment of Mg at grain boundaries. After annealing at 300°C for 0.5 h, the tensile strength of Zn– 1Mg alloy decreased from 254.92 to 170.93 MPa, while the elongation significantly increased by a factor of 14.3 from 0.55% to 8.43%. These findings provide valuable insights into an effective post-processing approach for tailoring the microstructure and resultant mechanical properties of LPBF-fabricated Zn and its alloys.

Statistical analysis of the development of the plant production industry by the example of changes in the average yield of grain crops in the XX century. Part 1. Period 1900 - 1933.

The work is devoted to studying the development of the crop production industry in the twentieth century. The theory of cyclical production and change of technological structures is chosen as a working theory. The average yield of grain crops in the Russian Empire and the Russian Soviet Federative Socialist Republic was determined to indicate production development. The choice of average grain yield is justified by its 'vital role in agriculture in the specified period. The change in the studied indicator is considered in the period from 1900 to 1933. The work provides a 'visual, graphical, historical, and statistical analysis of changes in the average yield of grain crops. The period from 1900 to 1933 is proposed to be divided into smaller periods consisting of H years, defined as small. For each small period, a statistical analysis is carried out, which includes calculating probabilistic characteristics, checking the average yield values for abnormal values, the presence of changes in the indicator during the period, and the nature of this change. Dividing the time interval into small periods allows us to study the change in yield in more detail and identify factors influencing this process. For each period, a hypothesis is put forward about the type of changes, and the acceptance or non-acceptance of the hypothesis is justified. The statistical analysis results are considered within the framework of past events identified during historical analysis. Building a model of changes in average yield during the period under review allows us to assess the industry’s past development and suggest possible future development scenarios. Analyzing the results of a statistical study in combination with historical context will provide a deeper understanding of the reasons for changes in yields and their impact on the development of the industry.