Orientated Nanometer-Sized Fragmentation of TiC Particles by Electropulsing
✍ Scribed by W. Zhang; M. Sui; Y. Zhou; Y. Zhong; D. Li
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 195 KB
- Volume
- 4
- Category
- Article
- ISSN
- 1438-1656
No coin nor oath required. For personal study only.
✦ Synopsis
longer coarsened sample it has moved to almost exactly zero mean curvature. The probability for a point on the interface to have solid near-spherical shapes has decreased substantially during coarsening while the probability for a point on the interface having liquid near-spherical shapes does not evolve significantly during coarsening time. In fact, in the sample that has experienced the longer coarsening we find a number of isolated spheres of liquid. These spheres do not coarsen significantly since the diffusion coefficient in the solid is much smaller than that in the liquid. In areas of strong negative mean curvature solid is deposited while in areas of strong positive mean curvature material is removed. While in both cases the actual interface area shrinks, it is not clear how H and K evolve. The evolution of both is coupled and furthermore depends on the local gradient in the velocity of the interface, [8] which itself depends on the local and global microstructure. This once more indicates the complexity of the morphological evolution process.
The evolution of dendritic microstructures during isothermal coarsening for Al-15 wt.-%Cu was studied. Using an automated serial-sectioning technique we obtained three-dimensional reconstructions of the dendritic microstructures coarsened for different lengths of time. These reconstructions can also be used to determine plots of the probability density of the mean and Gaussian curvatures. These plots show quantitatively the increase in size scale of a solid±liquid mixture that is expected during coarsening. Moreover, these plots reveal formerly inaccessible details such as the area fractions of various interfacial shapes and the manner in which interfaces with these shapes evolve in time. Information on the three-dimensional morphology will advance substantially our understanding of the dendrite coarsening process and will provide insights into the coarsening process that can be used to improve theoretical descriptions and simulations of the entire solidification process.