| 21. |
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| 22. |
- Guldris Leon, Lorena, 1983, et al.
(författare)
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Understanding Mineral Liberation during Crushing Using Grade-by-Size Analysis - A Case Study of the Penuota Sn-Ta Mineralization, Spain
- 2020
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Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Coarse comminution test-work and modeling are powerful tools in the design and optimization of mineral processing plants and provide information on energy consumption. Additional information on mineral liberation characteristics can be used for assessing the potential of pre-concentration stages or screens in the plant design. In ores of high-value metals (e.g., Ta, W), standard techniques-such as the mineralogical quantification of grain mounts by quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) or chemical analysis by X-ray fluorescence (XRF) can be challenging, due to the low relative abundance of such valuable minerals. The cost of QEMSCAN is also a limiting factor, especially considering the large number of samples required for the optimization of coarse comminution. In this study, we present an extended analytical protocol to a well-established mechanical test of interparticle breakage to improve the assessment of coarse mineral liberation characteristics. The liberation of ore minerals is a function of the rock texture and the difference in size and mechanical properties of the valuable minerals relative to gangue minerals and they may fraction in certain grain sizes if they behave differently during comminution. By analyzing the bulk-chemistry of the different grain size fractions produced after compressional testing, and by generating element by size diagrams, it is possible to understand the liberation characteristics of an ore. We show, based on a case study performed on a tantalum ore deposit, that element distribution can be used to study the influence of mechanical parameters on mineral liberation. This information can direct further mineralogical investigation and test work.
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| 23. |
- Hedström, Peter, et al.
(författare)
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Load partitioning between single bulk grains in a two-phase duplex stainless steel during tensile loading
- 2010
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 58:2, s. 734-744
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Tidskriftsartikel (refereegranskat)abstract
- The lattice strain tensor evolution for single bulk grains of austenite and ferrite in a duplex stainless steel during tensile loading to 0.02 applied strain has been investigated using in situ high-energy X-ray measurements and finite-element modeling. Single-grain X-ray diffraction lattice strain data for the eight austenite and seven ferrite grains measured show a large variation of residual lattice strains, which evolves upon deformation to the point where some grains with comparable crystallographic orientations have lattice strains different by 1.5 x 10(-3), corresponding to a stress of similar to 300 MPa. The finite-element simulations of the 15 measured grains in three different spatial arrangements confirmed the complex deformation constraint and importance of local grain environment.
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| 24. |
- Hosseini, Seyed, 1981, et al.
(författare)
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Characterization of the Surface Integrity induced by Hard Turning of Bainitic and Martensitic AISI 52100 Steel
- 2012
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 1:1, s. 494 - 499
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Konferensbidrag (refereegranskat)abstract
- Depending on the process parameters and the tool condition, hard turned surfaces can consist of a “white” and a “dark” etching layer having other mechanical properties compared to the bulk material. X-ray diffraction measurements revealed that tensileresidual stresses accompanied with higher volume fraction of retained austenite are present in the thermally induced white layer. While compressive residual stresses and decreased retained austenite content was found in the plastically created white layer. The surface temperature was estimated to be ~1200 C during white layer formation by hard turning.
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| 25. |
- Hryha, Eduard, 1980, et al.
(författare)
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Carbon Control in PM Sintering: Industrial Applications and Experience so Far
- 2012
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Ingår i: Proc. of EURO PM2012 Congress & Exhibition, 16-19 September 2012, Basel, Switzerland. - 9781899072231 ; 1, s. 265-270
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Konferensbidrag (refereegranskat)abstract
- Challenges in controlling carbon potential during sintering of steel powder have been discussed in many experimental and theoretical studies. The main issues lie within the complex thermodynamics and kinetics of processing atmosphere chemistry in continuous sintering furnaces. Although many models have tried to address the problem, many of these have rarely come to reality and become an industrial practice.The purpose of this article is to summarize these discussions and investigate the interaction of the atmosphere constituents with the sintered compact within a sintering furnace. Considering an industrial practice perspective, the paper ensures the PM Industry with a fresh new look into the understanding of the furnace operations and provides recommendations to improve the control of the furnace conditions. As an example, existing furnace installation utilizing Linde SINTERFLEX technology allows monitor and/or control the furnace atmosphere. Article describes reduction of oxides and carbon potentials to enable optimization of the production parameters.
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| 26. |
- Hryha, Eduard, 1980, et al.
(författare)
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Influence of the Steel Powder Type and Processing Parameters on the Debinding of PM Compacts with Gelatin Binder
- 2014
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Ingår i: Journal of Thermal Analysis and Calorimetry. - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926. ; 118:2, s. 695-704
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Tidskriftsartikel (refereegranskat)abstract
- Binders present an important part of the powder metallurgy technology as they are vital to provide efficient powder agglomeration and/or lubrication during shaping. At the same time, they have to be easily removed from the compacts during initial stages of sintering without any harmful effect for the base material, as well as for the environment. Therefore, behavior of gelatin as a binder for stainless- and tool-steel gas-atomised powder compacts was studied by thermal analysis and electron microscopy. Thermal analysis showed that peak mass-loss occurred in the range between 340 and 370 C, depending on the base powder and heating rate. Risk for base powder oxidation at temperatures below 425 C was detected. Based on the obtained results, it is recommended to perform debinding at *425 C after applying a heating rate of around 7.5 C min-1. Only in this way efficient enough binder removal can be obtained concurrently to avoiding base powder oxidation.
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| 27. |
- Hryha, Eduard, 1980, et al.
(författare)
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Process Control System for Delubrication of PM Steels
- 2012
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Ingår i: Acta Metallurgica Slovaca. - 1335-1532. ; 18:2-3, s. 60-68
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Tidskriftsartikel (refereegranskat)abstract
- Lubricants are important additive in powder metallurgy (PM) steels as they are needed to improve powder compressibility and reduce tool wear. Removal of the lubricant results in production of number of gas species that can have harmful effect on the base material. Current paper describes process gas monitoring system for delubrication control that is built on industrially available gas sensors. Experimental results indicate that accurate delubrication process control can be performed by utilizing only CO2 and O2 sensors. It is recommended to perform delubrication below 500°C in dry inert atmospheres in the case of modern ethylene bis stearamide based lubricants.
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| 28. |
- Huang, Shuo, et al.
(författare)
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Thermal Expansion, Elastic and Magnetic Properties of FeCoNiCu-Based High-Entropy Alloys Using First-Principle Theory
- 2017
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Ingår i: JOM. - : Springer. - 1047-4838 .- 1543-1851. ; 69:11, s. 2107-2112
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Tidskriftsartikel (refereegranskat)abstract
- The effects of V, Cr, and Mn on the magnetic, elastic, and thermal properties of FeCoNiCu high-entropy alloy are studied by using the exact muffin-tin orbitals method in combination with the coherent potential approximation. The calculated lattice parameters and Curie temperatures in the face-centered-cubic structure are in line with the available experimental and theoretical data. A significant change in the magnetic behavior is revealed when adding equimolar V, Cr, and Mn to the host composition. The three independent single-crystal elastic constants are computed using a finite strain technique, and the polycrystalline elasticity parameters including shear modulus, Young's modulus, Pugh ratio, Poisson's ratio, and elastic anisotropy are derived and discussed. The effects of temperature on the structural parameters are determined by making use of the Debye-Gruneisen model. It is found that FeCoNiCuCr possesses a slightly larger thermal expansion coefficient than do the other alloys considered here.
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| 29. |
- Hörnqvist Colliander, Magnus, 1979, et al.
(författare)
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High-temperature crack growth in a Ni-base superalloy during sustained load
- 2014
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093. ; 609, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- he high-temperature sustained load crack growth behaviour of a Ni-base superalloy was investigated using a combination of mechanical testing in controlled atmosphere, fractographical and microanalytical investigations, and finite element modelling. The results show that the local crack front geometry is un- even on two scales – jaggedness on the scale of 100 μm was observed in all specimens, whereas mm- scale waviness could occasionally be observed. The jaggedness can be explained by a percolation-type crack growth along weaker grain boundaries, whereas the large-scale waviness is presumably due to larger regions of the material having specific grain texture with high crack growth resistance. The un-even crack front is shown to potentially have considerable effects on the loading conditions at the crack tip, whereas ligaments of un-cracked material in the crack wake are deemed to have less effect on the crack tip loading due to their low area fraction. The ligaments fail intergranularly in the wake as the crack grows in the present case, as opposed to by creep fracture as previously proposed. Finally, the plastically deformed regions about the crack and crack tip are shown not to exhibit any elevated oxygen levels, implying that the damage in these regions is purely mechanical.
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| 30. |
- Jaladurgam, Nitesh Raj, 1993, et al.
(författare)
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Macro- and micro-mechanical behaviour of a γ′ strengthened Ni-based superalloy at cryogenic temperatures
- 2021
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- In-situ neutron diffraction was performed during tensile deformation of Ni-base superalloy, Haynes 282, at 20, 100 and 300 K. Two distinct uni-modal microstructures with fine (20 nm) and coarse (200 nm) \(\gamma^\prime\) particles were investigated. On the macro-scale yield strength increased and ductility decreased with decreasing temperature, although most significant decrease in ductility occurred between 100 and 20 K. The work hardening differed between the two microstructures, but was independent of temperature for each microstructure. On the micro-scale intergranular elastic interactions mainly lead to a transfer of the load to grains with the $\left<200\right>$ parallel to the tensile axis. No further load re-distribution between matrix and particles occurred in the microstructure with fine \(\gamma^\prime\), where shearing of precipitates lead to co-deformation at all temperatures. In the coarse \(\gamma^\prime\) microstructure, the load was transferred intragranularly from matrix to particles, in addition to the intergranular load transfer. The particles initially behaved elastically while the matrix deformed plastically, but at higher stresses a change in load partitioning indicated that also the \(\gamma^\prime\) phase underwent plastic deformation as a result of the elastic stress build-up from the load partitioning. The tendency for, and effect of, plastic deformation of \(\gamma^\prime\) increased with decreasing temperature.
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