Abstract
Tensile, fatigue, fracture toughness, and creep experiments were performed on a commercially available magnesium-aluminum alloy (AM60) after three processing treatments: (1) as-THIXOMOLDED (as-molded), (2) THIXOMOLDED then thermomechanically processed (TTMP), and (3) THIXOMOLDED then TTMP then annealed (annealed). The TTMP procedure resulted in a significantly reduced grain size and a tensile yield strength greater than twice that of the as-molded material without a debit in elongation to failure (ε f ). The as-molded material exhibited the lowest strength, while the annealed material exhibited an intermediate strength but the highest ε f (>1 pct). The TTMP and annealed materials exhibited fracture toughness values almost twice that of the as-molded material. The as-molded material exhibited the lowest fatigue threshold values and the lowest fatigue resistance. The annealed material exhibited the greatest fatigue resistance, and this was suggested to be related to its balance of tensile strength and ductility. The fatigue lives of each material were similar at both room temperature (RT) and 423 K (150 °C). The tensile-creep behavior was evaluated for applied stresses ranging between 20 and 75 MPa and temperatures between 373 and 473 K (100 and 200 °C). During both the fatigue and creep experiments, cracking preferentially occurred at grain boundaries. Overall, the results indicate that thermomechanical processing of AM60 dramatically improves the tensile, fracture toughness, and fatigue behavior, making this alloy attractive for structural applications. The reduced creep resistance after thermomechanical processing offers an opportunity for further research and development.
| Original language | English |
|---|---|
| Pages (from-to) | 1386-1399 |
| Number of pages | 14 |
| Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
| Volume | 42 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 2011 |
Funding
This research was conducted, in part, through the Oak Ridge National Laboratory’s High Temperature Materials Laboratory User Program, which is sponsored by the United States Department of Energy, Office of Energy Efficiency, and Renewable Energy, Vehicle Technologies Program, and through the Oak Ridge National Laboratory’s SHaRE User Facility, which is sponsored by the Division of Scientific User Facilities, Office of Basic Energy Sciences, United States Department of Energy. A portion of this work was supported by the Faculty and Student Teams (FAST) Program, which is a cooperative program between the Department of Energy Office of Science and the National Science Foundation. The authors are grateful to Dr. Camden Hubbard, Oak Ridge National Laboratory, for assisting with the XRD characterization. The authors are also grateful to Messrs. Bryan Kuhr and Alex Ritter, Michigan State University, for their technical assistance with the SEM, XRD, and in-situ deformation characterization. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DEAC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.
| Funders | Funder number |
|---|---|
| Department of Energy Office of Science | |
| Division of Scientific User Facilities | |
| Faculty and Student Teams | |
| Office of Basic Energy Sciences | |
| United States Department of Energy | |
| National Science Foundation | |
| Office of Energy Efficiency and Renewable Energy | |
| Oak Ridge National Laboratory |