Increasing the mechanical properties of structural cast iron for machine-building parts by combined Mn – Al alloying

The object of research in this work was cast iron for machine-building parts, alloyed with Al. The possibility of improving the mechanical properties of cast iron by choosing the optimal Mn – Al combinations, depending on the carbon content in the cast iron, was determined. The study was carried out on the basis of available retrospective data of serial industrial melts by constructing the regression equation for the ultimate strength of cast iron in the three-factor space of the input variables C – Mn – Al. The optimization problem was solved by the ridge analysis method after reducing the dimension of the factor space by fixing the carbon content at three levels: C = 3 %, C = 3.3 %, and C = 3.6 %. It was found that the maximum values of the ultimate strength are achieved at the minimum level of carbon content (C = 3%) and are in the range of values close to 300 MPa. In this case, the Al content is in the range (2.4–2.6) %, and the Mn content is about 0.82 %. With an increase in the carbon content, there is a tendency to a decrease in the content of Mn and Al in the alloy, which is necessary to ensure the ultimate strength close to 300 MPa. The results of the ridge analysis of the response surface also showed that at the upper limit of the carbon content (C = 3.6%), it is not possible to reach the ultimate strength of 300 MPa in the existing range of Mn and Al variation. All solutions are verified for the following ranges of input variables C = (2.94–3.66) %, Mn = (0.5–1.1) %, Al = (1.7–2.9) %. Graphical-analytical descriptions of the optimal Mn – Al ratios are obtained, depending on the actual content of carbon in the alloy, which make it possible to purposefully select the optimal melting modes by controlling the tensile strength of the alloy

Effect of heavy metals on stem anatomical characteristics of Trapa natans L. from Skadar Lake (Montenegro)

This study aimed to analyze stem anatomical characteristics of Trapa natans from five Skadar Lake locations (L1 - Milovića bay, L2 – inflow of the Morača river, L3 - Kamenik, L4 - Grmožur, L5 - Lipovik) with different concentrations of Cu, Mn, Zn, Co and Pb, during the summer period of the year 2012. Cross sections of stem were made using cryotechnic procedure. For all analyzed quantitative anatomical parameters, the minimum values at the location L2 were recorded, with the presence of maximum content for all investigated metals in stem of Trapa natans. On the other hand, except for cobalt, at the location L4 the minimum concentration for all investigated metals were recorded. Plants collected from this location have the largest average values of the most measured anatomical parameters. The results of Discriminant Analysis showed that plants from different location could be clearly classified into three groups according to their stem quantitative anatomical characteristics which corresponds with heavy metals content. Our research also showed that there is no statistically significant correlation between the content of most investigated metals (Co, Cu, Pb and Zn) and the values of anatomical parameters. Statistically significant negative correlation was found between Mn content in stem and values of two anatomical characters (stem cross-sectional area and Mn content, r = - 0.88; p < 0.05; number of hypodermal cell layers and Mn content, r = - 0.90; p < 0.05).

Sensitivity to Mn content mechanical properties of phase composition of ADI

The effect of manganese content on the phase composition and mechanical properties was studied on ADI materials that are isothermally quenchеd at different temperatures. ADI samples with Mn content of 0.78% and 0.24% were analyzed. The final structure of the cast iron was created by austenitizing heating at 900 ° C for 30 minutes. and subsequent isothermal quenching in liquid tin at temperatures of 310, 330, 350, 380 ° C for samples with high manganese content and at 350, 370 ° C for samples with low content. It is shown that increasing the manganese content increases the amount of residual austenite under the same quenching conditions. This enhances the positive role of the TRIP effect on the hardening processes. In particular, ADI with a high content of Mn show a higher rate of strengthening at the initial region of loading diagram, higher hardness and increased damping capacity. Instead, due to the embrittlement action of manganese, such materials have lower mechanical characteristics, which determined fracture moment. It was found that for the same quenching conditions, deformation to fracture and toughness are reduced by half on samples with higher manganese content. The negative effect of manganese on the fatigue is less significant, because the embrittlement action is compensated by phase transformations in the crack head, which inhibits its spread under cyclic loading. Due to the fact that manganese enhances the positive role of the TRIP effect but decrease fracture résistance, it is proposed to use ADI materials with high Mn content in products that operate in conditions of wear but are not subject to extreme stress. Keywords: ADI materials, manganese alloying, isothermal hardening, TRIP effect, retained austenite, strengthening, hardness. damping capacity.

Mitigation of CaCO3 Influences on Ipomoea batatas Plants Using Bacillus megaterium BSM 2894 var.

Under Egyptian soil conditions, when phosphorus fertilizers were applied to the soil, it gets fixed and converts to unavailable form, leading to low solubility for the plant. This study were fulfilled on sweet potato (cv. Beauregard) under undesirable soil properties (CaCO3 10.8 vs 11.3%) using Bacillus megaterium DSM 2894 strain under different five mono calcium phosphate (CSP) levels [(69(CSP20); 138(CSP40); 207 (CSP60); 276 (CSP80) and 345 ((CSP100) kg ha-1 of calcium superphosphate (CSP)] to arise the potential efficiency of some nutrients uptake and decease the applied total amount of CSP in 2019 and 2020 seasons. The results mentioned that highest values were obtained by inoculated plants with DSM2894 strain under 20, 60 and 100% of CSP for all studied nutrients content in both seasons, except Mn content in the 2019. Also, inoculated plants with DSM2894 under previous treatments for all tuberous root nutrients content, except Fe and Zn contents in both seasons, in addition protein and anti-radical power and total yield. Statistically, leaf nutrients uptake and tuberous root content were highly significant affected by DSM and CSP combination. Appling of phosphorus fertilizer with DSM2894 mixture was gave the best values as compared with phosphorus fertilizer or DSM2894, individually.

Strengthening Mechanism and Carbide Precipitation Behavior of Nb-Mo Microalloy Medium Mn Steel

This study investigates the strengthening mechanism and carbide precipitation behavior of medium Mn steel with Nb-Mo microalloy after cyclic quenching and austenite reverse transformation treatment. The results show that the Nb/Mo element not only precipitates (Nb,Mo)C in the grains, hindering the movement of dislocations and increases the strength, but also segregates at the austenite/ferrite grain boundary, thus delaying the transformation from austenite to ferrite. In addition, a large amount of nano-scale cementite is retained after cyclic quenching and austenite reverse transformation, which has a positive effect on the proportion of retained austenite in medium Mn steel. Moreover, the carbides with small size and low Mn content are dissolved, and the decomposed C and Mn content are beneficial to the nucleation of austenite during the intercritical annealing process at a temperature of 690 °C.

Ferrimagnetic–ferromagnetic phase transition in Mn4N films favored by non-magnetic In doping

The ferrimagnet Mn4N forms a family of compounds useful in spintronics. In a compound comprising non-magnetic and magnetic elements, one basically expects the compound to become ferromagnetic when the proportion of the magnetic element increases. Conversely, one does not expect ferromagnetism when the proportion of the non-magnetic element increases. Surprisingly, Mn4N becomes ferromagnetic at room temperature when the Mn content is decreased by the addition of In atoms, a non-magnetic element. X-ray magnetic circular dichroism measurement reveals that the magnetic moment of Mn atoms at face-centered sites, Mn(II), reverses between x = 0.15 and 0.27 and aligns parallel to that of Mn atoms at corner sites, Mn(I), at x = 0.27 and 0.41. The sign of the anomalous Hall resistivity also changes between x = 0.15 and 0.27 in accordance with the reversal of the magnetic moment of the Mn(II) atoms. These results are interpreted from first-principles calculation that the magnetic moment of Mn(II) sites which are the nearest neighbors to the In atom align to that of Mn(I) sites.

Characterization and origin of the Mn-rich patinas formed on Lunéville château sandstones

The formation of iron- and/or manganese-rich dark patinas on sandstones is a common natural phenomenon that occurs also on building stones. Lunéville château, in eastern France, presents such patinas that developed either under natural conditions (rain and time) or after an accidental fire and exposure to significant amounts of water as part of attempts to extinguish the fire. The present study aimed at characterizing both types of patinas in an effort to determine their formation mechanisms and Mn sources. In both cases, Mn required for patina formation likely derives from the reductive dissolution of Mn-rich minerals present in pristine sandstones, as suggested by the contrasting mineralogy and chemistry of Mn-rich phases present in the bulk and in the patina of a given building block. Reduced Mn species then migrate to the exposed surface of building blocks where they are re-oxidized via undetermined processes. Patinas developing “naturally” over time result from the alternation of wetting-reducing and drying-oxidizing cycles and appear to be composed of birnessite. Patinas formed after the 2003 fire result from this single accidental event and form a much thinner, heterogeneous, and discontinuous layer of poorly crystalline lithiophorite at the sandstone surface (∼ 0–150 µm compared to ∼ 300–600 µm for “natural” patinas). The lack of Mn-rich patinas on areas of Lunéville château is likely related to the lower Mn content of pristine sandstone blocks.