Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7971632 | Materials Science and Engineering: A | 2018 | 10 Pages |
Abstract
Significant improvement of high temperature strength of 2219 alloy was achieved by addition of equal atom percentages (at%) of Sc and Zr and using a novel three-stage heat treatment route. Processing of the alloy involved casting in a water-cooled copper mould with a cooling rate in the range of 102 to 103 K/s. This was followed by direct ageing of the cast alloy at 375â¯â to form thermally stable L12 type coherent Al3(Sc, Zr) precipitates in the matrix. Subsequently, the alloy was solutionized at 535â¯â and further aged at 200â¯â which caused the formation of highly dense θâ²â² (Al3Cu) and θⲠ(Al2Cu) precipitates. From microstructural characterization it was found that the high number density of these precipitates is due to heterogeneous nucleation on pre-existing Al3(Sc, Zr) precipitates. Presence of Al3(Sc, Zr) precipitates together with high number density of θâ²â² and θⲠprecipitates results in remarkably high 0.2% proof stress of 456â¯MPa at room temperature, 295â¯MPa at 200â¯Â°C and 227â¯MPa at 250â¯Â°C along with 5% ductility. It was found that Al3(Sc, Zr) precipitates also suppress the coarsening of θâ²â² and θⲠprecipitates thus making them thermally stable at high temperature.
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
S. Mondol, S. Kashyap, S. Kumar, K. Chattopadhyay,