scholarly journals The Microstructural Evolution, Tensile Properties, and Phase Hardness of a TiAl Alloy with a High Content of the β Phase

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2757 ◽  
Author(s):  
Ning Cui ◽  
Qianqian Wu ◽  
Zhiyuan Yan ◽  
Haitao Zhou ◽  
Xiaopeng Wang
Keyword(s):  
Tensile Properties ◽  
Room Temperature ◽  
Tial Alloy ◽  
Microstructural Analysis ◽  
Phase Content ◽  
Tial Alloys ◽  
Β Phase ◽  
Room Temperature Ductility ◽  
One Step ◽  
Equiaxed Grains

In this paper, the microstructure, deformability, tensile properties, and phase hardness of the Ti–43Al–2Cr–0.7Mo–0.1Y alloy with a high β phase content were investigated. Microstructural analysis showed that the β phase precipitated not only at the colony boundaries but also inside the lamellae due to its high content. A high-quality forging stock was prepared through one-step noncanned forging. The total deformation reached above 80%, suggesting that the alloy has good hot deformability compared to other TiAl alloys. The deformed microstructure was composed of fine and equiaxed grains due to dynamic recrystallization. The high β phase content was shown to contribute to the decomposition of the initial coarse lamellae. Tensile testing showed that the alloy has good room-temperature ductility, even if the β phase content reaches above 20%. This is inconsistent with a previous study that showed that a large amount of the hard β phase is detrimental to the room-temperature ductility of TiAl alloys. Nanoindentation testing showed that the hardness of the β phase in the current alloy is about 6.3 GPa, which is much lower than that in the Nb-containing TiAl alloys. Low hardness benefits the compatible deformation among various phases, which could be the main reason for the alloy’s good room-temperature ductility. Additionally, the influence of various β stabilizers on the hardness of the β phase was also studied. The β phase containing Nb had the highest hardness, whereas the β phase containing Cr had the lowest hardness.

scholarly journals Effect of Multi-Directional Forging on the Microstructure and Mechanical Properties of β-Solidifying TiAl Alloy

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1381 ◽  
Author(s):  
Ning Cui ◽  
Qianqian Wu ◽  
Kexiao Bi ◽  
Jin Wang ◽  
Tiewei Xu ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Room Temperature ◽  
Tial Alloy ◽  
Alloy Composition ◽  
Cast Alloy ◽  
Lamellar Microstructure ◽  
Hot Deformation Behavior ◽  
Tial Alloys ◽  
Β Phase ◽  
Ductile Brittle Transition Temperature

This study systematically investigated the influence of multi-directional forging (MDF) on the microstructural evolution, hot deformation behavior, and tensile properties of a β-solidifying TiAl alloy. The initial lamellar microstructure of an as-cast alloy was remarkably refined and homogenized by three-step MDF. High temperatures and multi-pass deformations were conducive to the decomposition of lamellae. A crack-free billet was obtained through three-step MDF, with a deformation temperature of 1250 °C and a forging speed of 0.1 mm/s, indicating that MDF can be applied to β-solidifying TiAl alloys by the proper control of the alloy composition and process parameters. Microstructural observation showed that the billet mainly consists of fine and equiaxed γ grains and a small amount of β phase. The tensile properties of the multi-directional forged alloy were also significantly improved, due to microstructure refinement. The ultimate tensile strength (UTS) and elongation (δ) at room temperature were 689.4 MPa, and 0.83%, respectively. The alloy exhibits excellent ductility at 700 °C. When the temperature was increased to 700 °C, the UTS decreased to 556 MPa and δ increased to 5.98%, indicating that the alloy exhibits excellent ductility at 700 °C. As the temperature further increased to 750 °C, δ dramatically increased to 46.65%, indicating that the ductile-brittle transition temperature of the alloy is between 700 °C and 750 °C.

Microstructure Transformation of a Refined High Nb Containing TiAl Alloy

2013 ◽  
Vol 747-748 ◽  
pp. 38-43 ◽  
Author(s):  
Li Hua Chai ◽  
Liang Yang ◽  
Jian Peng Zhang ◽  
Zhi Yong Zhang ◽  
Lai Qi Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Tial Alloy ◽  
High Strength ◽  
Temperature Limit ◽  
Tial Alloys ◽  
Β Phase ◽  
Α Phase ◽  
Refined Microstructure ◽  
Fully Lamellar ◽  
Sem Microstructure

High Nb containing TiAl alloys have been investigated traditionally as potential high temperature structural materials because of their high strength, good oxidation and creep resistance. However, the poor ductility and fracture toughness at room temperature limit their application, which could be improved by controlling microstructure to get refine and homogeneous fully lamellar structure. In this study, a high Nb containing TiAl alloy alloying Mn, B and Y with refined microstructure was produced. The solidification path was analyzed by DSC and SEM microstructure of the alloy was observed, after heating at a certain temperature for 1-24hrs and then quenching in water. The dissolution of β phase was also investigated. The results showed that the β phase could decompose only by heating in single β or near α phase field.

Microstructure Design for Enhancement of Room-temperature Ductility in Multi-component TiAl Alloys

MRS Advances ◽  
2019 ◽  
Vol 4 (25-26) ◽  
pp. 1523-1529 ◽  
Author(s):  
Ryosuke Yamagata ◽  
Yotaro Okada ◽  
Hideki Wakabayashi ◽  
Hirotoyo Nakashima ◽  
Masao Takeyama
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Significant Contribution ◽  
Volume Fraction ◽  
Microstructure Design ◽  
Tial Alloys ◽  
Volume Fractions ◽  
Β Phase ◽  
Room Temperature Ductility

AbstractEffects of microstructure constituents of α2-Ti3Al/γ-TiAl lamellae, β-Ti grains and γ grains, with various volume fractions on room-temperature ductility of γ-TiAl based alloys have been studied. The ductility of the alloys containing β phase of about 20% in volume increases to more than 1% as the volume fraction of γ phase increases to 80%. However, γ single phase alloys show very limited ductility of less than 0.2%. The present results, thus, confirmed the significant contribution of β phase to enhancement of the room-temperature ductility in multi-component TiAl alloys.

scholarly journals Hot Deformation Behavior and Microstructural Evolution of a Novel β-Solidifying Ti–43Al–3Mn–2Nb–0.1Y Alloy

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2172 ◽  
Author(s):  
Qianqian Wu ◽  
Ning Cui ◽  
Xiaohong Xiao ◽  
Xiaopeng Wang ◽  
Ertuan Zhao
Keyword(s):  
Tial Alloy ◽  
Processing Map ◽  
Large Angle ◽  
Deformation Condition ◽  
Hot Deformation Behavior ◽  
Tial Alloys ◽  
Ductile Brittle Transition Temperature ◽  
High Elongation ◽  
One Step ◽  
Average Size

In this paper, the hot deformability and mechanical properties of a novel Mn- and Nb- containing TiAl alloy were studied systematically with the use of isothermal compression experiments. The results show that the alloy has low deformation resistance and a low activation energy (392 KJ/mol), suggesting that the alloy has good hot deformability. A processing map was established, which shows that the present alloy has a smaller instability region and wider hot working window compared with other TiAl alloys. Microstructural observation shows that the initial lamellae completely transformed into fine equiaxial γ grains when the alloy was compressed at 1200 °C/0.01 s−1, which corresponds to the optimum deformation condition. Based on the above results, an intact TiAl billet was successfully fabricated by one-step large deformation using a four-column hydraulic machine. The microstructure of the billet is almost completely composed of recrystallized γ grains with large angle boundaries. Tensile testing shows the billet exhibits high tensile strength (780 MPa) and high elongation (1.44%) simultaneously, which benefits from fine γ grains with an average size of 4.9 μm. The ductile–brittle transition temperature is between 750–800 °C.

High Temperature Deformation Behavior of Beta-Gamma TiAl Alloy

2007 ◽  
Vol 539-543 ◽  
pp. 1531-1536 ◽  
Author(s):  
J.S. Kim ◽  
You Hwan Lee ◽  
Young Won Kim ◽  
Chong Soo Lee
Keyword(s):  
High Temperature ◽  
Deformation Behavior ◽  
Tial Alloy ◽  
Microstructural Analysis ◽  
Processing Condition ◽  
Simulation Method ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Β Phase ◽  
Dynamic Materials

In this study, high-temperature deformation behavior of newly developed beta-gamma TiAl alloys was investigated in the context of the dynamic-materials model (DMM). Processing maps representing the efficiency of power consumption for microstructure evolution were constructed utilizing the results of compression test at temperatures ranging from 1000oC to 1200oC and strain rates ranging from 10-4/s to 102/s and Artificial Neural Network simulation method. With the help of processing map and microstructural analysis, the optimum processing condition for the betagamma TiAl alloy was investigated. The role of β phase was also discussed in this study.

Influence of Rolling Temperature on Microstructure and Tensile Properties of AZ31 Sheets

2007 ◽  
Vol 546-549 ◽  
pp. 311-314 ◽  
Author(s):  
Da Quan Li ◽  
Qu Dong Wang ◽  
Wen Jiang Ding
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Tensile Properties ◽  
Room Temperature ◽  
Microstructural Analysis ◽  
Rolling Texture ◽  
Az31 Alloy ◽  
Rolling Temperature ◽  
The Poor ◽  
Different Temperatures

Microstructure and tensile properties of AZ31 rolled at different temperatures were characterized. Rolling of extruded AZ31 plates was carried out at room temperature, 573K, 623K and 673K. Cold rolling of extruded AZ31 plates was difficult due to the poor formability at room temperature. And deformation twinning plays an important role in rolling of AZ31 alloy at room temperature. The microstructural analysis showed that the nucleation of dynamic recrystallization (DRX) occurred at 573K, DRX was almost completed at 623K and grain growth was determined at 673K. The ultimate tensile strength (UTS) as large as 377MPa was achieved after rolled at 573K. And the anisotropy in strength was obviously examined due to the rolling texture. The anisotropy reduced as rolling temperature increasing from 573K to 673K and this may be attributed to the completion of DRX.

Influences of Hydrogenation on Tensile Properties of Ti40 Alloy

2012 ◽  
Vol 549 ◽  
pp. 757-761
Author(s):  
Xue Min Zhang ◽  
Yong Qing Zhao ◽  
Peng Sheng Zhang ◽  
Yong Nan Chen ◽  
Feng Ying Zhang ◽  
...  
Keyword(s):  
Brittle Fracture ◽  
Tensile Properties ◽  
Hydrogen Content ◽  
Room Temperature ◽  
Hydrogen Addition ◽  
Microstructure Observation ◽  
Β Phase ◽  
Solution Strengthening ◽  
New Phase ◽  
Fcc Structure

The influence of hydrogenation on microstructure and tensile properties of Ti40 alloy has been investigated. The microstructure observation reveals that a new phase called η phase with FCC structure appears at the grainboundaries when the hydrogen content above 0.3 wt.%. With increasing hydrogen contents, the strength first increases and then decreases, and the ductility decreases as the specimens tensioned at both room temperature and 700oC. These phenomenons are resulted from the solution strengthening of hydrogen addition in Ti40 alloy with single β phase. As the hydrogen content increases, the fracture mode changes from dimple to cleavage fracture for specimens tensioned at room temperature. When tested at 700oC, the morphology of fracture surfaces in the specimens are all characterized by polygonal grains and the fractograph exhibits typically “sugar candy” brittle fracture for the specimen with 0.5wt% H.

Ultrafine Fully-Lamellar Structures in Two-Phase γ-TiAl Alloys

1996 ◽  
Vol 460 ◽  
Author(s):  
P. J. Maziasz ◽  
C. T. Liu
Keyword(s):  
Room Temperature ◽  
Interlamellar Spacing ◽  
Hot Extrusion ◽  
Processing Parameters ◽  
High Temperature Strength ◽  
Two Phase ◽  
Tial Alloys ◽  
Room Temperature Ductility ◽  
Heat Treated ◽  
Fully Lamellar

ABSTRACTSpecial ultrafine fully-lamellar microstructures have been found recently in γ-TiAl alloys with 46–48 at.% Al, when they are processed or heat-treated above the α-transus temperature (Tα). Hot-extrusion above Tα also produces a refined colony or grain size. Refined-colony/ultrafine-lamellar (RC/UL) microstructures produce an excellent combination of room-temperature ductility and high-temperature strength in Ti-47Al-2Cr-2Nb (at.%) alloys. UL structures generally have an average interlamellar spacing of 100–200 nm, and have regularly alternating γ and α2 lamellea, such that they are dominated by γ/α2 interfaces with relatively few γ/γ twin boundaries. The focus of this study is how variations in processing parameters or alloy composition affect formation of the UL structure, particularly the α2 component.

scholarly journals Effect of cold-rolling on mechanical properties of Haynes 25 cobalt-based superalloy

10.30544/248 ◽  
2017 ◽  
Vol 23 (1) ◽  
pp. 31-45 ◽  
Author(s):  
Padina Ajami Ghaleh Rashidi ◽  
Hossein Arabi ◽  
Seyed Mehdi Abbasi
Keyword(s):  
Cold Rolling ◽  
Tensile Properties ◽  
Annealing Time ◽  
Room Temperature ◽  
Crack Nucleation ◽  
Microstructural Analysis ◽  
Time Range ◽  
High Annealing ◽  
Cold Rolling And Annealing ◽  
Cold Rolled

Effect of cold-rolling and annealing time on the microstructure, hardness and the tensile properties of Haynes 25 superalloy at room-temperature and 760 °C were investigated in this research. Hot-rolled and solutionized alloy of Haynes 25 was subjected to cold-rolling with different amounts of reductions, i.e. 5%, 10%, 20%, 30% and 35%. After that, all cold-rolled samples were annealed at 1230 °C for a period of time from 2 to 120 min. Microstructural analysis showed that for annealing time range from 30 to 120 min, the rate of grains coarsening remained approximately stable in all cold-rolled samples. On the other hand, the hardness results showed that expected decreasing trend of hardness did not occur after annealing of the cold-rolled samples at 1230 °C; on the contrary, hardness increased moderately in the range time from 10 to 120 min. Tensile properties after annealing of the cold-rolled samples at room temperature and 760 °C decreased. Loss of the tensile properties can be related to the high annealing temperature. According to the experimental results, decreasing trend of tensile properties and increasing trend of hardness is linked to the formation of hcp phase after annealing at 1230 °C for 30 min. Even though the hcp phase is a hard phase, the interface between fcc and hcp phases provides suitable sites for crack nucleation and propagation.

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