Hot workability of γ + α2 titanium aluminide: Development of processing map and constitutive equations
15 Aug 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 551, pp 169-186
TL;DR: In this paper, a hot isothermal compression test is carried out on reaction synthesized and homogenized titanium aluminide alloys at different temperatures and strain rates using Gleeble thermomechanical simulator.
Abstract: Gamma titanium alumindes are intermetallics, which have very narrow working range. Hot isothermal working is the most suitable process for hot working of alloy. Accordingly, hot isothermal compression test is carried out on reaction synthesized and homogenized titanium aluminide alloys at different temperatures and strain rates using Gleeble thermomechanical simulator. Three alloys of Ti48Al2Cr2Nb0.1B (atom%) have been used in the study. Stress–strain data obtained from the test has been used to construct processing map, which indicates the safe and unsafe working zone. Strain rate sensitivity and Zener–Hollomon parameter has been calculated. Further, constitutive equations have been generated and verified. It is found that alloy has good workability in the temperature range of 1223–1423 K at strain rates of 0.01–0.001 s −1 . In this range of parameters, the alloys nearly follow the constitutive equations.
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TL;DR: In this paper, the hot deformation characteristics of 7075 aluminum alloy (AA7075) were investigated by means of hot compression tests carried out in the temperature range of 200-450°C and strain rate range of 0.0003-1-s−1.
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15 Jan 2016-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the deformation behavior and dynamic recrystallization of a β-solidifying TiAl alloy was investigated by means of isothermal compression tests in a temperature range of 1100 −1225 −C and strain rate range of 0.01 −0.05 −1.
Abstract: Hot deformation behavior and dynamic recrystallization (DRX) of a β-solidifying TiAl alloy Ti–43Al–2Cr–2Mn–0.2Y (at%) were investigated by means of isothermal compression tests in a temperature range of 1100–1225 °C and strain rate range of 0.01–0.05 s−1. A processing map at a true strain 0.8 was developed based on the dynamic materials model. The current alloy possesses a wide processing window, and the optimum deformation condition is 1175–1225 °C/0.05 s−1. The main softening mechanism is DRX of γ grains. The DRX proceeded preferentially at triangle boundaries, and subsequently in the lamellae. Both deformation temperature and strain rate have an obvious impact on the microstructural evolution. The partial DRX occurred when the alloy deformed at low temperature and high strain rate. Some remnant lamellar structures existed due to the plastic anisotropy of lamellar colony. With the increase of temperature and /or the decrease of strain rate, the lamellae were effectively broken down into fine grains, and a relatively complete DRX occurred. Dynamic recovery is the main deformation mechanism for β0 phase, which promotes the compatible deformation between γ and α2 phases and prevents premature cracks. Additionally, the DRX mechanism of γ phase was investigated through TEM observations. The DRX of γ grains begins with the formation of sub-boundaries, followed by a process of rearrangement of sub-boundaries to form new grains.
56 citations
TL;DR: In this paper, the high temperature flow behavior of as-extruded Ti-47.5Al-Cr-V alloy has been investigated at the temperature between 1100 and 1250°C and the strain rate range from 0.001 s−−1 to 1 s−-1 by hot compression tests.
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TL;DR: In this article, high temperature compressive deformation behaviors of a high Nb-containing PM-TiAl alloy (Tie45Al e7Nb-0.3 W, at%) were investigated at temperatures ranging from 1050 � C to 1200 � C, and strain rates from 0.001 s − 1 to 1 s � 1.
48 citations
References
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TL;DR: Bulk metal working processes are carried out at elevated temperatures where the occurrence of simultaneous softening processes would enable the imposition of large strains in a single step or multi-step process.
Abstract: Bulk metal working processes are carried out at elevated temperatures where the occurrence of simultaneous softening processes would enable the imposition of large strains in a single step or multi...
622 citations
TL;DR: In this article, a statistical model of point defect disorder in ordered compounds is presented and applied to Ti3Al and TiAl using input data generated with embedded-atom potentials.
544 citations
TL;DR: A review of superplasticity in polycrystalline materials can be found in this article, where the authors present an overview of these new developments using the established behavior of conventional metallic alloys as a standard for comparison with the mechanical properties of new materials.
Abstract: The ability to achieve a high tensile ductility in a polycrystalline material is of interest both from a scientific point of view and also because of potential applications in the materials forming industry. The superplasticity of conventional metallic alloys is now well-documented and understood reasonably well. However, the field of superplasticity has expanded recently beyond the traditional metallic alloys to include evidence of superplastic-like behavior in a very wide range of new and advanced materials. To date, superplasticity has been reported in mechanically alloyed metals, metal matrix composites, ceramics, ceramic matrix composites and intermetallic compounds. This review presents an overview of these new developments using the established behavior of conventional metallic alloys as a standard for comparison with the mechanical properties of these new materials. As well be demonstrated, the new materials often exhibit significant differences in their flow characteristics in comparison with the traditional superplastic metallic alloys. The successful utilization of superplastic materials in forming applications requires an understanding of the failure processes occurring in the materials in terms of both the localization of external flow and the accumulation of internal damage through the nucleation and growth of cavities. These problems are also addressed in this review.
427 citations
28 Feb 1995-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effects of microstructure on tensile properties and deformation-fracture behavior are analyzed for deformation temperatures below and above the brittle-ductile transition.
Abstract: Deformation and fracture behavior of two-phase γ-TiAl alloys were investigated under monotonic tension loading conditions for duplex and lamellar microstructural forms. The effects of microstructure on tensile properties and deformation-fracture behavior are analyzed for deformation temperatures below and above the brittle-ductile transition. The crack initiation toughness and associated strains near the crack tip are used to explain the inverse relationship between ductility and toughness observed at room temperature. Fracture resistance behavior and toughening mechanisms at room temperature are explained in terms of microstructure and deformation anisotropy. The competition between the effects of grain size and lamellar spacing or tensile and toughness properties is discussed.
243 citations