scholarly journals Influence of decomposition of oversatured liquid solutions on the structure and microhardness of quickly curing alloys of the Pb–Sn system

2020 ◽  
Vol 64 (4) ◽  
pp. 391-397
Author(s):  
V. G. Shepelevich ◽  
O. N. Belaya ◽  
E. Yu. Neumerzhytskaya
Keyword(s):  
High Speed ◽  
Liquid Solution ◽  
Solid Solution Hardening ◽  
Softening Effect ◽  
Hardening Mechanism ◽  
Alloy Foil ◽  
Supersaturated Solid Solutions ◽  
Liquid Solutions ◽  
Interphase Boundaries ◽  
Melt Cooling

The results of studies of the structure and microhardness of foil alloys of the lead–tin system obtained by high-speed cooling from the liquid phase are presented. The foil sample had the following dimensions: length – up to 10 cm, width – up to 1 cm, and thickness – 30–80 microns. Melt cooling rate was not less than 105 K/s. A rapidly cooled foil is chara cterized by a dispersed structure. The size of the discharge of tin and lead does not exceed 5 μm. The specific surface of the interfacial boundaries achieve 1.7 μm–1. Due to supercooling, a microcrystalline structure forms in the foil. The average lengths of chords of random secants on lead and tin grain sections in the Pb–73 at.% Sn alloy foil are 0.8 and 1.8 μm respectively. The texture of (111) lead and (100) tin is formed in the foil of alloys of the lead – tin system under certain conditions. The formation of the structure of lead alloys containing from 20 to 95 at.% tin is due to the occurrence of spinodal decomposition of a supersaturated liquid solution, and, in other alloys, due to decay by the mechanism of formation and growth of nuclei of crystalline phases. The stratification of the liquid solution leads to the formation of areas enriched in lead and tin, which contribute to the formation of crystallization centers that are equally distributed in the volume of the foil. The microhardness of the foil alloys, whose compositions are close to eutectic, is less than the microhardness of massive alloys of the same composition, which is associated with the softening effect of grain boundaries and interphase boundaries. Exposure of these alloys at room temperature causes an increase in microhardness due to a decrease in slippage at the boundaries. The decomposition of supersaturated solid solutions of Pb–5 at.% Sn and Sn–1 at.% Pb alloys leads to a decrease in microhardness due to the weakening of the effect of the solid solution hardening mechanism. The results of the study can be used to create fusible solders, bearing alloys, alloys for cable sheaths with improved physicochemical properties.

scholarly journals Nickel-Based Alloy Dry Milling Process Induced Material Softening Effect

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3758 ◽  
Author(s):  
Jun Zha ◽  
Zelong Yuan ◽  
Hangcheng Zhang ◽  
Yipeng Li ◽  
Yaolong Chen
Keyword(s):  
High Speed ◽  
Softening Temperature ◽  
Milling Process ◽  
Dry Milling ◽  
Milling Force ◽  
Softening Effect ◽  
Milling Temperature ◽  
Nickel Based Alloy ◽  
Alloy Softening ◽  
Milling Forces

Improving the cutting efficiency is the major factor for improving the processing of nickel-based alloys. The novelty of this research is the calibrated SiAlON ceramic tool dry milling nickel-based alloy process. Firstly, the nickel-based alloy dry milling process was analyzed through the finite element method, and the required milling force and temperature were deduced. Then, several dry milling experiments were conducted with the milling temperature, and the milling force was monitored. The change in cutting speeds was from 400 m/min to 700 m/min. Experimental results verified the reduction of the dry milling force hypothesized by the simulation. The experiment also indicated that with a cut depth of 0.3 mm, cut width of 6 mm, and feed per tooth of 0.03 mm/z, when milling speed exceeded 527.52 m/min, the milling force began to decrease, and the milling temperature exceeded the nickel-based alloy softening temperature. This indicated that easy cutting could be realized under high-speed dry milling conditions. The interpolation curve about average temperature and average milling forces showed similarity to the tensile strength reduction with the rise of temperature.

scholarly journals Microstructure and mechanical properties of high-manganese-containing high-speed twin-roll cast Al-Mn-Si alloy strips and their cold-rolled sheets

2020 ◽  
Vol 326 ◽  
pp. 06004
Author(s):  
T.Ha Nguyen ◽  
Ram Song ◽  
Yohei Harada ◽  
Shinji Muraishi ◽  
Shinji Kumai ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
High Speed ◽  
Solid Solution Hardening ◽  
Columnar Dendrite ◽  
Dispersion Hardening ◽  
High Manganese ◽  
Solution Hardening ◽  
Cold Rolled ◽  
Twin Roll

Al-Mn based alloys with high-manganese content are expected to have improved mechanical properties due to solid solution hardening and/or dispersion hardening. However, the increase of Mn solubility of the alloy is difficult by using the conventional DC casting. In order to solve this problem, in the present study, we focused on the twin-roll casting method which is characterized by high cooling rates. Several kinds of high Mn-containing Al-Mn-Si alloy strips were fabricated by using a vertical-type high-speed twin-roll caster equipped with a pair of water-cooled copper rolls. Direct temperature measurement of the liquid melt during the casting was also performed. The alloy strips of various compositions containing up to 4 Mn and 2 Si (wt%) were successfully obtained. By observing the microstructure of the cross section of the strip, we found the characteristic solidified structure. The solidified structure consisted of three layers. Two solidified shells with a columnar dendrite structure grew from the roll surfaces toward the strip center. In the mid-thickness region, the band structure consisting of equiaxed dendrites and globular grains was observed between the solidified shells. Very fine primary particles were observed in the matrix near the strip surface, while, relatively coarse particles with blocky and needle-like shape were observed in the central band of the as-cast strip. The electric conductivity measurement was performed for the as-cast strips. Mn solubility in Al matrix was estimated from the obtained values. The estimated Mn solubility in the Al-2Mn-xSi strips was between 1.5 ~ 1.8wt% Mn. It was over 1.43wt%Mn for the Al-4Mn-xSi strips. We found that the Mn solubility of the as-cast strips was considerably high. The strips were cold-rolled to the sheets and then annealed at various conditions. They were subjected to the tensile tests, and the effects of solid solution hardening and dispersion hardening are discussed.

Cement free castable. Part 5. CFC on alumina hydraulic binder

2020 ◽  
pp. 25-35
Author(s):  
Yu. E. Pivinskii ◽  
P. V. Dyakin
Keyword(s):  
Heat Treatment ◽  
Heat Treatment Temperature ◽  
Thermomechanical Properties ◽  
Treatment Temperature ◽  
Comparative Assessment ◽  
Mullite Formation ◽  
Softening Effect ◽  
Hardening Mechanism ◽  
Hydraulic Binder ◽  
Silica Sols

Cement free castables (CFC) based on alumina hydraulic binders by the hardening mechanism are similar to low-cement castables (LCC) and ultra-low-cement castables (ULCC). They are characterized by significant strengthening in the heat treatment temperature range of 200‒300 °C and sharp softening in the 600‒1000 °C range. By introducing silica sols or microsilica into their composition, it is possible not only to reduce or eliminate the softening effect, but also to increase their strength after firing due to the process of mullite formation. Compared to LCC, CFC based on alumina binders are characterized by improved thermomechanical properties. A comparative assessment of CFC based on hydraulic binders with other types of refractory concretes is given.

scholarly journals Novel Mechanical Characterization of Austenite and Ferrite Phases within Duplex Stainless Steel

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1352
Author(s):  
Hossein Besharatloo ◽  
Marcel Carpio ◽  
José-María Cabrera ◽  
Antonio Manuel Mateo ◽  
Gemma Fargas ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
High Speed ◽  
Mapping Technique ◽  
Small Scale ◽  
Processing Conditions ◽  
Excellent Correlation ◽  
Electron Backscattered Diffraction ◽  
Interphase Boundaries

The microstructure and micromechanical properties of the constitutive phases of a particular duplex stainless steel in various processing conditions have been characterized. Hardness (H), elastic modulus (E) and H/E cartography maps were obtained by using a high-speed nanoindentation mapping technique. Small-scale H and E evolution at different processing conditions has been investigated by statistical analysis of a large number of nanoindentations (10,000 imprints per sample). Two mechanically distinct phases, ferrite (α) and austenite (γ), were deconvoluted from this dataset using Ulm and Constantinides’ method, with the remaining values assigned to a third mechanical phase linked to composite-like (containing α/γ interphase boundaries) regions. These mechanical property phase assessments were supplemented by overlaying crystallographic phase maps obtained by electron backscattered diffraction. An excellent correlation between microstructure and small-scale mechanical properties was achieved, especially when considering the ratio H/E.

A Polar Liquid Zwitterion Does Not Critically Destroy Cytochrome c at High Concentration: An Initial Comparative Study with a Polar Ionic Liquid

2019 ◽  
Vol 72 (2) ◽  
pp. 139 ◽  
Author(s):  
Kosuke Kuroda ◽  
Chiaki Kodo ◽  
Kazuaki Ninomiya ◽  
Kenji Takahashi
Keyword(s):  
Ionic Liquid ◽  
Cytochrome C ◽  
Soret Band ◽  
Liquid Solution ◽  
Acetate Solution ◽  
High Concentration ◽  
Liquid Solutions ◽  
High Concentration Range ◽  
Ionic Liquid Solution ◽  
Better Than

A polar carboxylate-type zwitterion with a small volume of water can dissolve cytochrome c without significant disruption, compared with the case of a popular polar carboxylate-type ionic liquid, 1-ethyl-3-methylimidazolium acetate. A change in the Soret, Q, and 615nm bands was not observed in the 80 wt-% polar zwitterion solution, whereas a shift in the Soret band, diminishing Q band, and appearance of the 615nm band was found in the 80 wt-% polar ionic liquid solution. It suggests that concentrated polar ionic liquid solutions critically disrupt the structure of cytochrome c, and the polar zwitterion solution used in this study was better than a 1-ethyl-3-methylimidazolium acetate solution in a high concentration range.

The role of atom-probe field ion microscopy in alloy development and phase transformation studies

1994 ◽  
Vol 52 ◽  
pp. 822-823
Author(s):  
M. K. Miller ◽  
R. Jayaram ◽  
K. F. Russell
Keyword(s):  
Grain Boundaries ◽  
Gas Turbines ◽  
Atom Probe ◽  
Solid Solution Hardening ◽  
Alloy Development ◽  
Probe Field ◽  
Hardening Mechanism ◽  
Boron Segregation ◽  
Large Effort

One of the important parameters in the design of new materials is the distribution of the alloyingelements in the microstructure and whether these elements are involved in the formation of precipitates or in segregation to internal interfaces such as grain boundaries. The atom probe field ion microscope is an extremely effective tool for these types of fine scale characterizations. Recently, therehas been a large effort to develop new, more efficient materials for high temperature applications such as gas turbines. A candidate material for this application is NiAl. However, the low temperature ductility of NiAl is extremely small and hinders fabrication. Therefore, attempts have been made to alleviate these problems with the use of microalloying additions such as boron. The atom probe has beenused to determine the location of boron in the microstructure and correlate its distribution with themechanical properties. Atom probe analyses have revealed that the solubility of boron in NiAl is extremely low and most of the excess boron is precipitated in the form of ultrafine MB2 precipitates as shown in Fig. 1. In addition, boron segregation to the grain boundaries has been observed, Fig. 2. Theobserved increase in the yield strength is therefore primarily due to a precipitation hardening mechanism with a contribution from solid solution hardening and this offsets the beneficial effect of the boron at the grain boundaries.

Temperature and Strain-Rate Effect to Mechanical Behavior of Mo-Cr Alloy Cast Iron

2011 ◽  
Vol 704-705 ◽  
pp. 918-922
Author(s):  
Jing Kui Ruan ◽  
Ming Mao Hu
Keyword(s):  
Cast Iron ◽  
Strain Rate ◽  
High Speed ◽  
Tensile Yield Strength ◽  
Strengthening Effect ◽  
Softening Effect ◽  
Auto Panel ◽  
Alloy Cast Iron ◽  
Alloy Cast ◽  
Alloy Iron

Mo-Cr alloy cast iron is the most important material often used to make auto panel dies. To study high-speed machining process of auto panel dies, the material’s elastic modulus and fracture critical values of Mo-Cr alloy iron at 20°C-800°C were studied based on the high temperature elongation test. The material’s stress-strain relation curves at various temperatures (20°C-500°C) and various strain-rates (500/s-5000/s) were studied and the dynamic tensile yield strength values were obtained by dynamic SHPB(Split Hopkinson Pressure Bar) high-speed compression test. The test observation showed that Mo-Cr alloy iron has heat resistance and its behavior is between toughness and brittleness materials. Its toughness is enhanced with temperature increasing. At 20°C-500°C and strain-rates (500/s-5000/s) the dynamic tensile yield strength is decreased about 17％-24％ by temperature softening effect and is increased about 56％-70％ by strain-rate strengthening effect. The strain-rate strengthening effect prevails over temperature softening effect. Keywords: Auto panel die; Mo-Cr alloy cast iron; SHPB; Temperature softening effect; Strain-rate strengthening effect

Research on Dynamic Constitutive Relation of Materials Taking Account of Damage Evolution and Fracture Law for High Speed Cutting

2011 ◽  
Vol 188 ◽  
pp. 224-229
Author(s):  
J.Q. Li ◽  
Tao Tao Dong ◽  
Min Jie Wang
Keyword(s):  
Shear Band ◽  
Strain Rate ◽  
Constitutive Relation ◽  
Damage Evolution ◽  
High Speed ◽  
Adiabatic Shear Band ◽  
Adiabatic Shear ◽  
Damage Effect ◽  
Serrated Chip ◽  
Softening Effect

The adiabatic shear, which may produce serrated chip, usually occurs for a large number of materials in high speed machining. Adiabatic shear band is an important damage model for metals under high-velocity deformation process. The damage evolution of micro-voids in adiabatic shear bands resulted in material fracture finally. Now the thermal softening effect, the strain rate harding effect and the strain harding effect have been discussed extensively in literature, but there is very little research on its damage effect. Based on the experiments of predecessors, this paper presents a new damage evolution equation that is dependent on strain, strain rate and is suitable for the description of voids damage evolution in adiabatic shear band. The corresponding rate-dependent constitutive relation taking account of damage evolution and temperature are proposed. The predicted results are in good agreement with the experiment datum.

scholarly journals Application of Activated Carbon Obtained from Spent Coffee Ground Wastes to Effective Terbium Recovery from Liquid Solutions

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 630
Author(s):  
Lorena Alcaraz ◽  
Dayana Nathaly Saquinga ◽  
Francisco J. Alguacil ◽  
Esther Escudero ◽  
Félix A. López
Keyword(s):  
Activated Carbon ◽  
Kinetic Studies ◽  
Nitrogen Adsorption ◽  
Liquid Solution ◽  
Physical Activation ◽  
Solution Ph ◽  
Sem Images ◽  
Spent Coffee Ground ◽  
Liquid Solutions ◽  
Adsorption Desorption

A process aimed at the recovery of terbium from liquid solutions using activated carbon (AC) derived from spent coffee grounds (SCG) was assessed. AC was obtained using the hydro-alcoholic treatment of SCG, followed by the physical activation of the as-obtained product. The AC exhibited both microporous and mesoporous structures, which were shown by the corresponding nitrogen adsorption–desorption isotherms and scanning electron microscopy (SEM) images. In addition, a certain graphitic character was found in the micro-Raman measurements. By use of this AC, terbium adsorption was investigated, and the influence of solution pH, temperature, and the adsorbent amount on terbium uptake was tested. In addition, adsorption isotherms and kinetic studies were also evaluated. The best fit was found for the type-1 Langmuir isotherm and pseudo-second-order kinetics model. Thermodynamic studies revealed that terbium adsorption is an endothermic and spontaneous process. Terbium desorption by the use of acidic solutions was also investigated. This work demonstrated that it is possible to recover this valuable metal from liquid solution using the present AC.

scholarly journals Effect of melt cooling rate on the microstructure and thermal properties of Al – Ge alloy

2020 ◽  
pp. 70-77
Author(s):  
Olga V. Gusakova ◽  
Yuliya M. Shulya ◽  
Hanna M. Skibinskaya ◽  
Vladimir E. Ankudinov
Keyword(s):  
Cooling Rate ◽  
Cross Section ◽  
High Speed ◽  
Eutectic Reaction ◽  
Melting Rate ◽  
Size Reduction ◽  
Scanning Calorimetry ◽  
Melt Cooling ◽  
Rapidly Solidified ◽  
Alloys Of The Al

The paper presents the results of comparing the microstructure of alloys of the Al – Ge system of eutectic and near- eutectic compositions synthesized at melt cooling rates of 102 and 105 K/s. It was shown by scanning electron microscopy that at a cooling rate of 102 K/s, crystallization starts with grain growth of the excess component and ends with a eutectic reaction. The microstructure of bulk samples is characterized by large inclusions of aluminum and germanium and heterogeneity of composition at sample cross section. The size reduction of phase particles of alloys of the Al – Ge system of eutectic and near-eutectic compositions is achieved using high-speed solidification. It is shown that the cooling rate of the melt increase causes size reduction of phase particles by 2–3 orders. The layering of the microstructure of the cross section of rapidly solidified foils was also revealed, and a mechanism for its formation was proposed taking into account changes in the solidification conditions over the thickness of the foil. Using differential scanning calorimetry, it was shown that an increase in the cooling rate provides a narrowing of the melting temperature range and an increase in the melting rate.

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