The effect of matrix microstructure and reinforcement shape on the creep deformation of near-γ titanium aluminide composites

Kampe, S. L.; Christodoulou, Julie; Feng, C.R.; Christodoulou, L.; Michel, D.J.

doi:10.1016/s1359-6454(97)00441-2

Cited by 19 publications

(13 citation statements)

References 36 publications

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“…If conditions are conducive to co-deformation, both components will commensurately deform, creating a multilithic metal matrix composite (MMMC) with approximately aligned DR-IMC "reinforcement" of an increased aspect ratio as a consequence of the deformation imposed. [10,11,12] …”

Section: A Generalmentioning

confidence: 99%

Co-deformation processing and modeling of In-Situ multiphase composites

Marte

Zahrah

Kampe

2004

Metall Mater Trans A

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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 TiB 2 particulate within a titanium trialuminide or near-␥ Ti-47Al matrix. Thus, an example of a resulting composite would be Ti-6Al-4V ϩ 40 vol pct (Al 3 Ti ϩ 30 vol pct TiB 2 ) or Ti-6Al-4V ϩ 40 vol pct (Ti-47Al ϩ 40 vol pct TiB 2 ), 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 TiB 2 within the DR-IMC, and by varying the percentage of DR-IMC within the metal matrix. In the former instance, variation of the TiB 2 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.

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Section: A Generalmentioning

confidence: 99%

Co-deformation processing and modeling of In-Situ multiphase composites

Marte

Zahrah

Kampe

2004

Metall Mater Trans A

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“…While finely spaced lamellar structures might be expected to provide good creep resistance owing to high strain hardening rates, these microstructures are not stable under all creep conditions. [7,8,31,36] Under severe temperature and stress conditions (more appropriately associated with hot-working than anticipated service conditions) the fine, equiaxed grains of a 2 and c that form at the lamellar colony boundaries control behavior, reducing activation energies to values associated with diffu-REVIEWS Fig. 3.…”

Section: Total Creep Strainmentioning

confidence: 99%

“…Thus, the refined structures remain stable until the conditions of hotworking or tertiary creep are met, and, in all cases studied, wrought boride-reinforced alloys with lamellar microstructures strain readily during tertiary creep as microstructural conversion kinetics are accelerated. [31] …”

Section: Total Creep Strainmentioning

confidence: 99%

“…Kampe and co-workers [31] have recently reported that for the near-c composites Ti±47±2 V + 7.5 vol.-% TiB 2 and Ti± 47±2 Nb + 7.5 vol.-% (Ti,Nb)B tested at 800 C, the strain hardening exponent (n¢) averages 0.110 for lamellar matrix composites at 800 C versus 0.076 for composites with equiaxed matrices. Here, n¢ is part of a conventional powerlaw plasticity equation:…”

Section: Steady State Creep Behaviormentioning

confidence: 99%

“…5). [7,31] Microstructure also profoundly influences the total strain accumulated during creep. A significantly greater amount of strain must be accumulated before the onset of steady-state creep for fully lamellar structures than for fully equiaxed microstructures, and the steady state creep rates of equiaxed microstructures are greater than those of lamellar structures.…”

Section: Steady State Creep Behaviormentioning

confidence: 99%

See 2 more Smart Citations

The Role of Borides in Near-γ Titanium Aluminides

Christodoulou¹,

Flower²

2000

Adv. Eng. Mater.

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REVIEWSThis paper reviews how boride additions affect the microstructure, strength and creep properties of a 2 + c titanium aluminides. Important titanium boride structures in near-c alloys include TiB 2 and TiB; their structures and stability ranges are discussed first. Then, influences on matrix microstructureÐgrain refinement, enhanced microstructural conversion kinetics, and the stabilization of fine lamellar structureÐare elaborated upon, for matrix microstructure plays the most important role in determining mechanical properties. The combined effects of reinforcement and microstructure on mechanical behavior are then explored, illustrating how the incorporation of grain refiners, such as titanium borides, facilitates thermomechanical processing and enables the tailoring of microstructure to optimize specific mechanical properties.

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