| 1. |
- Antonsson, Tomas, et al.
(författare)
-
Liquid Ni-Fe penetration and recrystallisation in tungsten
- 2003
-
Ingår i: International journal of refractory metals & hard materials. - 0263-4368. ; 21:3-4, s. 159-170
-
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.
|
|
| 2. |
|
|
| 3. |
- Dhindaw, B. K., et al.
(författare)
-
Characterization of the peritectic reaction in medium-alloy steel through microsegregation and heat-of-transformation studies
- 2004
-
Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 35A:9, s. 2869-2879
-
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.
|
|
| 4. |
- Ekbom, Lars B., et al.
(författare)
-
Computer simulation of solution and growth processes during the initial stage of liquid phase sintering of tungsten heavy metal
- 2005
-
Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 34:5, s. 312-316
-
Tidskriftsartikel (refereegranskat)abstract
- In the initial stage of liquid phase sintering, particle dissolution and growth processes occur. The melting matrix penetrates the solid particle agglomerates. A fraction of the particles dissolves in the liquid matrix phase and the original powder size will initially be reduced. At the same time the agglomerates of particles are effectively separated. In a second stage larger particles grow in equilibrium with the matrix, whilst smaller, pure particles dissolve into the matrix and the mean particle size increases. When an equilibrium is reached, the solid particles start to grow in the liquid matrix phase in accordance with the ripening process. The initial stages of liquid phase sintering have been investigated by short time sintering under microgravity and are presented in a series of micrographs. Mathematical models for the 3 stages have been developed. Computer simulations of these different stages in the solution and growth processes have been used to visualise the change in particle size distribution.
|
|
