Twinning Mechanisms in Complex High Tm Intermetallic Compounds
Abstract
This program was divided into two sections involving two separate kinds of experiments: The first involved an investigation into the possibility of twinning in complex structures by inhomogeneous shears (without shuffles) possibly involving synchroshear, as we found to be important in HfV2. The second was an experimental investigation into the (low) temperature-stress regime within which twins nucleate. We were able to show using high resolution TEM, that the shear is inhomogeneous, since the plane of mirror symmetry is a particular set of planes in the structure. Second we were able to show that shuffles are not involved since shuffling should be a diffusion-like process and should become very sluggish at low temperatures. We did flow stress measurements down to 4K and found that the twinning process is active all the way down to at least 77K, strongly suggesting that shuffles are not part of the process. As a result, we were able to demonstrate for the first time that the synchroshear process actually appears to be the mechanism by which twinning occurs in this material.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 05, 1999
- Accession Number
- ADA362826
Entities
People
- David E. Luzzi
- David P. Pope
Organizations
- University of Pennsylvania