Co-deformation processing and modeling of In-Situ multiphase composites
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1/4/04
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Co-Deformation Processing and Modeling of In-Situ Multiphase Composites J.S. MARTE, T.F. ZAHRAH, and S.L. KAMPE A series of in-situ, deformation-processed metal matrix composites were produced by direct powder extrusion of blended constituents. The resulting composites are comprised of a metallic Ti-6Al-4V matrix containing dispersed and co-deformed discontinuously reinforced–intermetallic matrix composite (DR-IMC) reinforcements. The DR-IMCs are comprised of discontinuous TiB2 particulate within a titanium trialuminide or near- Ti-47Al matrix. Thus, an example of a resulting composite would be Ti-6Al-4V 40 vol pct (Al3Ti 30 vol pct TiB2) or Ti-6Al-4V 40 vol pct (Ti-47Al 40 vol pct TiB2), with the DR-IMCs having an aligned, high aspect ratio morphology as a consequence of deformation processing. The degree to which both constituents deform during extrusion has been examined using systematic variations in the percentage of TiB2 within the DR-IMC, and by varying the percentage of DR-IMC within the metal matrix. In the former instance, variation of the TiB2 percentage effects variations in relative flow behavior; while in the latter, varying the percentage of DR-IMC within the metallic matrix effects changes in strain distribution among components. The results indicate that successful co-deformation processing can occur within certain ranges of relative flow stress; however, the extent of commensurate flow will be limited by the constituents’ inherent capacity to plastically deform.
I. INTRODUCTION
CO-DEFORMATION processes use large macroscopic plastic strain to densify, bond, shape, or evolve desired microstructural features within a multiphase alloy composition or assemblage. Several conventional and familiar manufacturing techniques rely on the principles of codeformation, for example, bi- or multimetal pack rolling and cladding,[1] the processing of canned metal powders,[2] or deformation-processed in-situ metal matrix composites.[3,4,5] In each of these examples, successful processing relies on the compatible or commensurate deformation of at least two generally mechanically dissimilar materials. The ability to successfully co-deform dissimilar phases or components within a composite or process method is commonly assumed to rely upon the relative magnitude of the flow stresses of the participating components. That is, the components’ flow behavior and their inherent deformability will be influential in establishing if stable and commensurate (proportional) deformation will occur. However, the relative flow behavior of the components is often inequitably influenced by a relatively wide range of factors, including strain, strain rate, temperature, stress state, deformation texturing, and environment. Additional complexity may be present if dynamic changes in the interfacial character (i.e., chemical, thermodynamic, or bonding strength) between components occurs during processing. Traditionally, it is difficult to independently vary the relative flow behavior of the components of
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