Abstract/Details

High -strength, thermally-stable nanostructured materials


2006 2006

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Abstract (summary)

The properties of two technologically important precipitation-treatable alloys - Al 6061 and Inconel 718, that are deformed to large plastic strains at room temperature by machining, are presented.

The strong effect of prior density of precipitates on the consequent microstructure refinement during chip formation was determined by deforming Al 6061 of different tempers to varying levels of strain, by varying the tool rake angle. Chips cut from peak-aged 6061, consisting of a fine dispersion of precipitates, produced the finest microstructure and are composed of sub-100 nm grains. On the other hand, coarser precipitate distributions in over-aged 6061 and an absence of precipitates in solution-treated 6061 resulted in much coarser microstructures. Thermal stability of such nanostructured chips with different levels of strain and precipitate distributions is analyzed by studying evolution of Vickers micro-hardness and microstructure after different heat treatments. Chips produced from the peak-aged temper and over-aged temper soften following heat treatment while those from the solution-treated state first, gain strength before softening. The results are rationalized based on prior studies of the characteristics and kinetics of precipitation and coarsening in Al-Mg-Si systems.

It is then demonstrated that precipitate-stabilized nanostructured materials synthesized from a prototypical alloy system - Inconel 718, are extremely stable even after prolonged heat treatment for 240 hours at temperatures as high as one-half of the melting point. This extraordinary thermal stability is traced to the retention of a fine dispersion of precipitates in a nanostructured matrix even after extended heat treatment.

It is anticipated that general design principles garnered from understanding of the causal phenomena determining strengthening and thermal stability, can lead to the development of alloy systems for the manufacture of high-strength, thermally-stable nanostructured materials.

Indexing (details)


Subject
Industrial engineering;
Metallurgy;
Materials science
Classification
0546: Industrial engineering
0743: Metallurgy
0794: Materials science
Identifier / keyword
Applied sciences; High-strength; Large-strain deformation; Nanostructured; Thermally stable
Title
High -strength, thermally-stable nanostructured materials
Author
Shankar, Ravi
Number of pages
97
Publication year
2006
Degree date
2006
School code
0183
Source
DAI-B 68/02, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Advisor
Chandrasekar, Srinivasan; Compton, W. Dale; King, Alexander H.
University/institution
Purdue University
University location
United States -- Indiana
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3251694
ProQuest document ID
305264797
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305264797/abstract
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