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| 2. |
- Antonsson, Tomas, et al.
(författare)
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Liquid Ni-Fe penetration and recrystallisation in tungsten
- 2003
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Ingår i: International journal of refractory metals & hard materials. - 0263-4368. ; 21:3-4, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- Melt penetration in grain boundaries of solid tungsten has been investigated. Solid tungsten rods have been exposed to a nickel-iron melt saturated with tungsten and the penetration depth and the shape of the liquid channels have been examined. The solid tungsten samples have been treated in different ways like cold working, annealing and recrystallisation, before melt exposure. Important parameters for the penetration process are stresses, surface tensions, solution and kinetic effects. A new theoretical model for the penetration mechanism in cold worked samples is proposed. Rapid recovery of the grains in the penetrated areas of the cold worked samples was observed. This is discussed, as well.
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| 3. |
- Dhindaw, B. K., et al.
(författare)
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Characterization of the peritectic reaction in medium-alloy steel through microsegregation and heat-of-transformation studies
- 2004
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 35A:9, s. 2869-2879
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the phenomenon of the peritectic reaction was characterized in a medium-ailoy steel. Several directional solidification and thermal-analysis experiments were done to investigate the reaction process. Directional solidification experiments carried out did not tend to show any direct evidence of a peritectic reaction. Microsegregation studies on the directionally solidified samples and those solidified under isothermal conditions bring out some interesting features. It has been documented that if the segregation ratio for Ni is higher than that for Cr, there is a correlation that the peritectic reaction had occurred in that region. On the other hand, a higher Cr segregation ratio as compared to Ni showed the possibility that the liquid had directly transformed to gamma-austenite without undergoing a peritectic reaction. Measurement of energies of transformations and the analysis of their values in different segments of the cooling-curve differential thermal analysis (DTA) experiments have helped in understanding the peritectic reaction. It is revealed that the transformation is more like diffusionless transformation, where gamma-austenite directly precipitates from delta-ferrite. Indeed, this proposition is also supported by the segregation patterns for Cr and Ni obtained in the solidified samples of this steel during directional solidification and DTA experiments and also by calculations to show the presence of enough lattice defects or vacancies to aid the aforementioned transformation.
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| 4. |
- Dhindaw, B. K., et al.
(författare)
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Microstructure development and solute redistribution in aluminium alloys under low and moderate shear rates during rheo processing
- 2005
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 413, s. 156-164
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Tidskriftsartikel (refereegranskat)abstract
- Microstructural features and microsegregational behaviour of solute are studied in shear or stir-cast aluminium alloys under low and moderate shear rates. Alloys studied are Al-6.2% Cu, Al-7.3% Si and Al-13.2% Mg. In all the cases, microstructures of the primary pre-quench solid for stir-cast samples show rosette or ellipsoidal morphologies. Volume fractions of pre-quenched solid phase show significantly higher values for stir-cast alloys as compared to calculated. Microsegregation studies by microprobe analysis along the grains of the samples solidified under different treatment conditions show that stir casting changes the segregation pattern significantly. Except for Al-13.2% Mg alloys lower values than those calculated by Scheil's microsegregation equation are observed for other systems. A model for microstructure evolution during stir casting is presented. The microsegregation patterns have been discussed in terms of interaction between the diffusing solute and the vacancies migrating from solid into liquid.
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| 5. |
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| 6. |
- Kron, J., et al.
(författare)
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Comparison of numerical simulation models for predicting temperature in solidification analysis with reference to air gap formation
- 2004
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Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 17:5, s. 295-310
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Tidskriftsartikel (refereegranskat)abstract
- As a result of its influence on heat transfer between cast part and mould, air gap formation is an important problem for many casting processes. The general explanation for gap formation is that, as a result of stresses and distortions that are created from inhomogeneous cooling, shrinkage of the casting and expansion of the mould occur. In this paper, different thermomechanical approaches are applied to a well defined casting process using three commercial and one in-house codes and their predictions are compared with experimental findings. The experimental data were obtained from the solidification and subsequent cooling of cylindrical castings of eutectic Al-13% Si and ternary Al-7% Si-0.3% Mg alloys. Based on these findings, the major differences between the predictions of the models and the actual formation of the air gap are discussed.
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