In-Situ Neutron Diffraction Study of Aging of a Mg-Y-Nd-Zr Alloy (WE43): Effects of Precipitation on Individual Deformation Mechanisms
Abstract
There is an outstanding question regarding why the age hardening response of Mg alloys is not nearly as good as many competing Al alloys. It has recently been proposed that the effect is due to precipitate geometry, since most commercial Mg alloys form either basal plate-shaped precipitates (e.g. AZ alloys) or c-axis aligned rod-shaped precipitates (e.g. ZK alloys) [1], and these are among the least effective precipitate shapes to obstruct basal slip. It is further proposed that prismatic plate-shaped precipitates would be most effective for strengthening Mg alloys [1], and prior transmission electron microscopy studies have revealed that Mg-Y-Nd-Zr alloys form prismatic plate shaped precipitates during artificial aging. In-situ neutron diffraction experiments performed on Mg-Y-Nd-Zr alloy, WE43, in the solution heat treated and peak- and over-aged conditions, reveal that prismatic plate shaped precipitates do indeed strongly impede basal slip. However, as revealed by previous in-situ neutron diffraction and crystal plasticity studies of Mg alloys, hard deformation modes such as deformation twinning and non-basal slip are required for macroscopic yielding. These hard modes are not as strongly impeded by the prismatic plate shaped precipitates. This finding helps to explain why the age hardening response of Mg-Y-Nd-Zr alloys is not that great, and suggests that the main reason these alloys are so strong relates to potent solid solution strengthening, in addition to precipitation strengthening. It is concluded that the future alloy and process design strategies should focus on promoting high number densities of particles more than on particle shape.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2012
- Accession Number
- ADA566023
Entities
People
- B. Clausen
- F. J. Polesak Iii
- S. R. Agnew
Organizations
- University of Virginia