Creep Behavior and Microstructure of XD™ Titanium Aluminide

1990 ◽  
Vol 194 ◽  
Author(s):  
C. R. Feng ◽  
H. H. Smith ◽  
D. J. Michel ◽  
C. R. Crowe
Keyword(s):  
Heat Treatment ◽  
Creep Behavior ◽  
Titanium Aluminide ◽  
Lamellar Structure ◽  
Creep Mechanism ◽  
Creep Testing ◽  
Al Alloy ◽  
Creep Tests ◽  
Two Phase

AbstractThe creep behavior of extruded XD™ Ti-47at%Al/7.5v%TiB2 composite was investigated together with extruded Ti-46at%Al alloy. Prior to creep testing, both materials received a duplex heat-treatment at 1200°C for 16h plus 900°C for 8h. The creep tests were conducted at 69, 103 and 138MPa at 760°C in air. The microstructures of both materials prior to and after the creep testing were examined by TEM. The microstructures suggest that the formation of the TiAl/Ti3Al two-phase lamellar structure was the predominant creep mechanism.

scholarly journals Strain Rate during Creep in High-Pressure Die-Cast AZ91 Magnesium Alloys at Intermediate Temperatures

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 872
Author(s):  
Mónica Preciado ◽  
Pedro Bravo ◽  
José Calaf ◽  
Daniel Ballorca
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Magnesium Alloys ◽  
Creep Behavior ◽  
Metallic Phase ◽  
Creep Testing ◽  
Strain Rates ◽  
Die Cast ◽  
Az91 Magnesium ◽  
The Stability

During creep, magnesium alloys undergo microstructural changes due to temperature and stress. These alterations are associated with the evolution of the present phases at a microstructural level, creating different strain rates during primary and tertiary creep, and with the stability of the inter-metallic phase Mg17Al12 formed at these temperatures. In this paper, the results of creep testing of high-pressure die-cast AZ91 magnesium alloys are reported. During creep, continuous and discontinuous precipitates grow, which influences creep resistance. The creep mechanism that acts at these intermediate temperatures up to 150 °C is termed dislocation climbing. Finally, the influence of the type of precipitates on the creep behavior of alloys is determined by promoting the formation of continuous precipitates by a short heat treatment prior to creep testing.

Microstructural Changes During Long-Term Tension Creep of Two-Phase γ-Titanium Aluminide Alloys

1996 ◽  
Vol 460 ◽  
Author(s):  
M. Oehring ◽  
P. J. Ennis ◽  
F. Appel ◽  
R. Wagner
Keyword(s):  
Titanium Aluminide ◽  
Primary Creep ◽  
Creep Tests ◽  
Two Phase ◽  
Microstructural Changes ◽  
Deformation Processes ◽  
Interfacial Dislocations ◽  
Structural Parts ◽  
Heterogeneous Formation

ABSTRACTLong-term tension creep tests were performed on a Ti-48 at.% Al-2 at.% Cr alloy in order to assess the material behaviour under the intended service conditions for structural parts in turbine engines. Deformation processes and microstructural changes were investigated by TEM on a specimen loaded to 140 MPa for 5988 h at 700 °C. At lamellar boundaries the emission of interfacial dislocations was observed and is thought to contribute significantly to the high primary creep rate of the material. Under the creep conditions gliding dislocations apparently become locked by the heterogeneous formation of precipitates along their cores. Lamellar interfaces revealed ledges which indicates that they migrate during creep.

scholarly journals Creep Mechanisms of an Al–Cu–Mg Alloy at the Macro- and Micro-Scale: Effect of the S′/S Precipitate

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2907 ◽  
Author(s):  
Yongqian Xu ◽  
Lingwei Yang ◽  
Lihua Zhan ◽  
Hailiang Yu ◽  
Minghui Huang
Keyword(s):  
Steady State ◽  
Steady State Creep ◽  
Creep Mechanism ◽  
Mg Alloy ◽  
Tensile Creep ◽  
Precipitate Size ◽  
Minor Role ◽  
Al Alloy ◽  
Creep Tests ◽  
Precipitate Growth

A novel methodology combining the macro- and micro-creep techniques was employed to study the effect of S′/S precipitate growth on the creep mechanism of an Al–Cu–Mg alloy. An AA2524 alloy was pre-aged at 180 °C to obtain S′/S precipitates with various sizes. The results showed that the precipitate size increased approximately linearly to ≈32 nm, ≈60 nm, and ≈105 nm after 3 h, 6 h, and 12 h of pre-aging, respectively. The growth of precipitate could significantly shorten the primary creep stage, despite the fact that the steady-state creep behavior was similar to that of the as-received alloy, as revealed by the macro tensile creep tests at 180 °C and 180 MPa. This led to a stress exponent (2.4–2.5) of the Al alloy with various precipitate sizes that was quite close to that of the as-received Al alloy, implying a steady-state creep mechanism dominated by grain boundary sliding and dislocation interactions. Finally, the micro-creep tests showed a minor role of the precipitate size on the steady-state creep mechanism, as evidenced by the similar strain rate sensitivity (0.0169–0.0186), activation volume (≈27 b3), and the results of a detailed transmission electron microscopy analysis of all tested alloys.

Tensile and Creep Behavior of Ordered Orthorhombic Ti2A1Nb-Based Alloys

1990 ◽  
Vol 213 ◽  
Author(s):  
R.G. Rowe ◽  
D.G. Konitzer ◽  
A.P. Woodfield ◽  
J.C. Chesnutt
Keyword(s):  
Heat Treatment ◽  
Titanium Aluminide ◽  
Room Temperature ◽  
Single Phase ◽  
Two Phase ◽  
Creep Properties ◽  
Specific Strength ◽  
Heat Treated ◽  
Titanium Aluminide Alloys

ABSTRACTTitanium aluminide alloys with compositions near Ti-25A1-25Nb at.% were prepared by both rapid solidification and ingot techniques. Their tensile and creep properties were studied after heat treatment to produce various microstructures containing ordered orthorhombic (O) [1], ordered beta (βo), and α2 phases. It was found that these alloys had higher specific strength from room temperature to 760°C than conventional α2 alloys. Ductility and tensile strength of O+βo alloys were strongly dependent upon heat treatment, with the highest strength observed as-heat-treated, and the highest ductility after long term aging. The creep resistance of single phase O and two phase O+βo alloys was strongly dependent upon heat treatment.

Effect of Heat Treatment at (β+γ) Two Phase Region on Fracture Toughness in TiAl Intermetallic Compound

2019 ◽  
Vol 810 ◽  
pp. 21-26
Author(s):  
Makoto Hasegawa ◽  
Tomohiro Inui ◽  
Ivo Dlouhý
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Lamellar Structure ◽  
Treatment Time ◽  
Lamellar Microstructure ◽  
Phase Region ◽  
Two Phase ◽  
Temperature Range ◽  
Heat Treated ◽  
Fully Lamellar

Effects of holding temperature and time at (β+γ) two phase region on the microstructure of fully lamellar Ti-46Al-7Nb-0.7Cr-0.2Ni-0.1Si (mol%) intermetallic compounds are studies. Fully lamellar microstructure is observed after homogenization heat treatment for 3.6 ks at 1643 K (α single phase state). Fine β phased grains precipitate at fully lamellar structure after heat treatment of homogenized material at 1373 K. Holding the homogenized material for 72 ks at 1373 K decompose partially the lamellar structure. Heat treatment of homogenized material at 1273 K also precipitates the fine β phased grains in fully lamellar structure. In this temperature range, decomposition of lamellar structure is not observed up to 72 ks heat treatment. The toughness of homogenized material is ~ 15 MPa√m. Heat treatment of homogenized material at 1373 K and 1273 K for 3.6 ks indicates maximum fracture toughness in each temperature range. This may due to the precipitation of fine β phased grains. The fracture toughness decreases with the increase in heat treatment time up to 18 ks and/or 36 ks. Then, the value of fracture toughness became constant. Specimens heat treated at 1373 K for 36 ks and 72 ks indicate lower toughness than homogenized material. However, when the specimens are heat treated at 1273 K for 36 ks and 72 ks, the toughness is higher than that of homogenized material. This change is due to the decomposition of the lamellar structure.

Processing and Characterization of Al2Ti/Al 3Ti Two-Phase Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
M. J. Lukitsch ◽  
J. E. Benci
Keyword(s):  
Heat Treatment ◽  
Solution Heat Treatment ◽  
Hot Forging ◽  
Al Alloy ◽  
Two Phase ◽  
Al Content ◽  
Material Condition ◽  
Material Conditions ◽  
Lower Temperature ◽  
Cast Condition

ABSTRACTSeveral buttons of each of three binary Ti-Al alloys containing nominally 70, 71 and 72 at.% Al were prepared from elemental Ti and Al by plasma arc-melting. One button of each composition was then either solution heat-treated, subjected to a two-step heat treatment, or hot forged. Each composition and material condition was then characterized using SEM/EDS and microhardness testing. The results show that while all three compositions have a predominantly two-phase, coarse microstructure in the as-cast condition, it is possible to produce an essentially single phase material through an appropriate solution heat treatment for the two lower Al content alloys. A fine two-phase microstructure can be achieved through an additional, lower temperature heat treatment step. The microhardness results show that the solution heat treatment reduced the hardness for all three compositions compared to the as-cast condition while hot forging as-cast samples increased hardness. The 70% Al alloy has the highest hardness for all four material conditions studied while the 71% Al alloy has the lowest hardness in three of the four material conditions.

scholarly journals Primary Creep Behaviour of Two-Phase Titanium Alloy with Various Microstructure

2016 ◽  
Vol 61 (2) ◽  
pp. 683-688
Author(s):  
W. Ziaja ◽  
M. Motyka ◽  
K. Kubiak ◽  
J. Sieniawski
Keyword(s):  
Heat Treatment ◽  
Elevated Temperature ◽  
Creep Behaviour ◽  
Strong Dependence ◽  
Primary Creep ◽  
Fatigue Properties ◽  
Creep Tests ◽  
Two Phase ◽  
Treatment Conditions ◽  
Primary Creep Strain

Abstract Creep and fatigue properties of two-phase titanium alloys show strong dependence on microstructure, especially morphology of the α and β phases which can be controlled to certain extent by proper selection of hot working and heat treatment conditions. In the paper the creep behaviour of Ti-6Al-2Mo-2Cr alloy (VT3-1) at elevated temperature was modelled. Finite element analyses of primary creep stage were carried out taking into account some microstructural features of the two-phase alloy that were included in the physical model and different properties of α and β phases. In order to verify results of calculations distinct types of microstructure were developed in the alloy by heat treatment and creep tests were carried out at elevated temperature (450°C) at various stress levels. Based on the FEM simulations the effect of changes of some microstructure features on primary creep strain development was estimated.

Statistical analysis of creep behavior in thermoset and thermoplastic composites reinforced with carbon and glass fibers

2020 ◽  
pp. 030932472097663
Author(s):  
Francisco Maciel Monticeli ◽  
Ana Karoline dos Reis ◽  
Roberta Motta Neves ◽  
Luis Felipe de Paula Santos ◽  
Edson Cocchieri Botelho ◽  
...  
Keyword(s):  
Creep Behavior ◽  
Glass Fibers ◽  
Laminated Composite ◽  
Analytical Models ◽  
Thermoplastic Composites ◽  
Temperature Dependent ◽  
Creep Tests ◽  
Thermoset Composites ◽  
Strain Behavior ◽  
Sensitivity Range

The thermoplastic and thermoset laminates reinforced with different fibers generate variations in the laminated composite mechanical behavior. This work aims to analyze thermoplastic and thermoset composites creep behavior with a reduced number of experiments, applying curve-fitting analytical models (Weibull and Findley) and statistical approach (ANOVA, F-test, and SRM) in order to describe creep behavior. Creep tests were carried out using a design of experiments to define parameter levels, aiming to reduce the number of the experiments, keeping reliability relevance. The temperature shows a stronger influence of creep deformation compared with the use of distinct materials. Thermoplastic matrices seem to be more sensitive to deformation, decreasing the reinforcement contribution. On the other hand, the creep resistance of the thermoset matrix conducts a significant contribution of strain behavior for the reinforcement used. The Findley model showed a temperature-dependent response. While, the Weibull-based model exhibits temperature and material-dependence, ensuring a greater sensitivity range of the parameters applied, an essential factor for a more realistic method description.

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