ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
This work describes the microstructure and properties of a range of Al-(4-6)Mg-(1.2-1.6)Li-(0.3-0.4)Zr-(0-0.2)Sc alloys produced at Oxford University by spraycasting. Follow-ing hot isostatic pressing of the as-spraycast billets to close any porosity and to precipitate a¯ne, coherent dispersoid population, forging to a true strain of 1 at 250 and 400±C led to asubstantial re¯nement of the microstructure with grain sizes in the range 0.8 to 5¹m. A largeintra-granular orientation gradient with distance measured using EBSD showed that at 250±C,partial dynamic recrystallisation by progressive lattice rotation led to a `necklace' structure ofvery ¯ne grains surrounding larger deformed grains. At 400±C, dynamic recrystallisation oc-curred by nucleation of new grains at prior grain boundaries and triple points. The strengthof as-forged alloys was 200-350MPa and the high ductilities of up to 30% rendered the alloysamenable to post-forging cold work. A proof strength of 460MPa with 9.5% elongation wasachieved in a non-heat-treatable spraycast Al-6Mg-1.3Li-0.4Zr alloy, matching the best prop-erties of similar mechanically alloyed AA5091, and exceeding the properties of AA7010-T74.The as-forged alloys showed excellent thermal stability up to » 0.9Tm, with no abnormal graingrowth and grain size stagnation due to Zener pinning. Finally, strain rate sensitivity testingrevealed the potential for superplasticity at 400 and 500±C and strain rates of 0.001-0.05s¡1
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/13/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.519-521.1629.pdf
