Influence of equal channel angular extrusion processing on the physical, mechanical, and microstructural properties od Al-Cu-Li base alloys /
Al-Cu-Li base alloys offer an attractive property combination
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736824311&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Al-Cu-Li base alloys offer an attractive property combination of low density, high specific strength and modulus and exceptional cryogenic properties which makes them excellent candidates for a variety of aerospace applications. The superplastic behavior of the processed alloy is significantly dependent on the processing conditions. Recently, severe plastic deformation was found to be effective in producing an ultra-fine grained structure about 0.21um, which may permit lower superplastic forming temperatures and/or higher strain rates, thus cost effective. Equal channel angular extrusion has the advantage of producing superfine submicron grained structure by intense plastic deformation, which may improve the superplastic, and the room temperature mechanical properties of Al-Cu-Li base alloys. The influence of ECAE as a primary grain refinement process on the physical and mechanical properties, and microstructural evolution of Al- Cu-Li-Mg-Ag-Zr alloys was investigated through variations in thermomechanical processing conditions (heat treatment required for particle distribution, and extrusion temperatures, number of passes and route type). The effect of warm rolling as a secondary grain refinement process on the physical, mechanical, and microstructural properties of the ECAE processed alloys was assessed. An Al-Cu-Li-Mg-Ag-Zr alloy received in the form of superplastic sheets processed via rolling was employed to compare the superplastic response and room temperature mechanical properties of the ECAE processed alloys with the conventionally processed ones. ECAE processing successfully developed submicron grained structure <0.6um in Al-Cu-Li base alloys with initial grain size of -100um. ECAE processing has proven its ability to develop a superplastic AL-Cu-Li base alloy deformed at relatively low temperature of (0.77Tm) and intermediate strain rates (-10-3s-1) with high % elongation-to-fracture (>300%), which can achieve superplastic forming cost effectiveness through reduction in the production time. Sherby creep rate prediction is the model that best described the experimental-data for the processing conditions investigated. ECAE is an efficient process for the processing of the alloys designed for ambient and hence cryogenic applications in aerospace, where ultra-high strength and fracture toughness are required. ECAE processing effectively improved the room temperature mechanical properties of the alloys investigated in the T4 and T6 temper compared to that of the conventionally processed ones, regardless of the Cu-and-Li-contents. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xxvi, 304 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 288-296. |