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.

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.

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.

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.

Titanium Boride in High Nb Containing TiAl Alloy: Morphology and Effect on Mechanical Properties

2011 ◽  
Vol 415-417 ◽  
pp. 1121-1126
Author(s):  
Xiang Jun Xu ◽  
Jun Pin Lin ◽  
Yan Li Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
High Temperatures ◽  
Room Temperature ◽  
Tial Alloy ◽  
Cast Alloy ◽  
Harmful Effect ◽  
Titanium Boride ◽  
Creep Properties

The morphology of titanium boride in as-cast and as-forged Ti-45Al-8.5Nb-(W, B, Y) alloy containing 0.2at. % boron and the effect of borides on tensile and creep properties of the alloy are investigated. The results show that in as-cast alloy the morphology of boride appears mainly convoluted ribbons with some flakes and particles. With the extent of forging increases, the length of the ribbons decreases and their distribution is more uniform. The long ribbon in as-cast alloy is detrimental to tensile properties at both room temperature (RT) and high temperatures. The short ribbon in as-forged alloy is not harmful to RT tensile properties, but is harmful to tensile and creep properties at high temperatures. The harmful effect of the boride is due to the strain incompatibility of boride and matrix, which causes many cavities at boride/matrix boundaries and results in ultimate fracture.

Effect of Alloying and Thermal Processing on Mechanical Properties of TiAl Alloys

2016 ◽  
Vol 258 ◽  
pp. 501-505
Author(s):  
Alice Chlupová ◽  
Milan Heczko ◽  
Karel Obrtlík ◽  
Přemysl Beran ◽  
Tomáš Kruml
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Thermal Processing ◽  
Lamellar Microstructure ◽  
High Strength ◽  
Fatigue Behaviour ◽  
Tial Alloys ◽  
Working Temperature ◽  
Β Phase ◽  
Strength And Ductility

Two γ-based TiAl alloys with 7 at.% of Nb, alloyed with 2 at.% Mo and 0.5 at.% C, were studied. A heat treatment leading to very fine lamellar microstructure was applied on both alloys. Microstructure after the heat treatment was described and mechanical properties including fatigue behaviour were measured. The as-received material alloyed with C possesses high strength and very limited ductility, especially at RT. After application of selected heat treatment it becomes even more brittle; therefore, this process could be considered as not appropriate for this alloy. On the contrary, in the case of Mo alloyed material, both strength and ductility are improved by the heat treatment at RT and usual working temperature (~750 °C). Presence of the β phase is responsible for this effect. The selected heat treatment thus can be an alternative for this alloy to other thermomechanical treatments as high temperature forging.

Effects of Microstructure and Partial Melting on Tensile Properties of AZ91 Magnesium Cast Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 65-68 ◽  
Author(s):  
Tian Ping Zhu ◽  
Zhan W. Chen ◽  
Wei Gao
Keyword(s):  
Mechanical Properties ◽  
Partial Melting ◽  
Tensile Properties ◽  
Cast Alloy ◽  
Az91 Alloy ◽  
Β Phase ◽  
Interdendrite Region ◽  
Mg17al12 Phase ◽  
Az91 Magnesium ◽  
Cast Microstructure

Mechanical properties of AZ91 cast alloy depend strongly on the morphology (size and distribution) of the second (β-Mg17Al12) phase. It was observed that low ductility of AZ91 alloy was attributed to the brittle nature of the β phase particles at which microcracks initiated. These microcracks then coalesced contributing to the fracture of alloy. Quantitative study on microcracking progress revealed that cast samples with coarse microstructures fractured at low strain due to the non-uniform distribution of bulk blocky β particles at interdendrite region. These fracture surfaces exhibited clear cleavage mode. Fine cast microstructure presented quasicleavage fracture mode with clear dimple and tear ridges. The partial melting (and resolidification) heat treatment improved tensile properties, which was in disagreement with the available data from literature.

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.

scholarly journals Investigation of Slow Eutectoid Element on Tensile Properties and Superplasticity of a Forged SP700 Titanium Alloy

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1852
Author(s):  
Dong Han ◽  
Yongqing Zhao ◽  
Weidong Zeng ◽  
Junfeng Xiang
Keyword(s):  
Tensile Properties ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Microstructure Characteristics ◽  
Density Of Dislocations ◽  
Globular Microstructure ◽  
Β Phase ◽  
Elevated Temperature Tensile ◽  
Cr Addition

The tensile properties and superplasticity of a forged SP700 alloy with slow eutectoid element (1.5%Cr) addition were investigated in the present paper. The results of the microstructures showed that slow eutectoid element Cr has a significant influence on stabilizing the β phase and the SP700Cr alloy showed a uniform duplex and completely globular microstructure after annealing at 820 °C for 1 h and aging at 500 °C for 6 h. The results of the tensile tests showed that the yield strength, ultimate tensile strength and elongation of the alloy with optimized microstructure were 1312 MPa, 1211 MPa and 10% at room temperature, and the elongation was achieved to 1127% at 770 °C. Compared with that of the SP700 alloy, the strain rate sensitivity of the SP700Cr alloy showed a higher value. The microstructures after elevated temperature tensile tests showed that the higher density of dislocations and twins exists in SP700 alloy and the lower density of dislocations favor distribution in SP700Cr alloy. Based on the above results, the tensile properties and superplasticity of the forged SP700 alloy with 1.5% Cr addition was analyzed. In addition, microstructure characteristics were investigated by the TEM and EBSD technologies.

Study on the Influence of Compression Damage on Tensile Properties in Fully Lamellar TiAl-Based Alloy

2012 ◽  
Vol 482-484 ◽  
pp. 1713-1717
Author(s):  
Bin Tang ◽  
Chuan Jing Chen ◽  
Zhi Yong Xue ◽  
Chun Jing Wu ◽  
Shuang Shou Li
Keyword(s):  
Mechanical Property ◽  
High Temperature ◽  
Tensile Properties ◽  
Tensile Property ◽  
Room Temperature ◽  
Tial Alloy ◽  
Tensile Tests ◽  
Fully Lamellar ◽  
Compression Damage

The changes of the tensile properties of the full lamellar TiAl alloy under pre-compression were studied by means of pre-compression damage tests and tensile tests. The study indicated that：The changes of the tensile property of the damaged alloy at room temperature were different from that of high temperature. The mechanical property of the TiAl alloy degrades because of the present of the cracks, which decrease the load area of the alloy.

Study on the Microstructure and Fracture Mechanism of Stable β Phase Containing Tial Alloy

2014 ◽  
Vol 941-944 ◽  
pp. 1517-1521
Author(s):  
Xiang Bin Yi ◽  
Zhi Yuan Rui ◽  
Rui Cheng Feng ◽  
Yan Rui Zuo
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Room Temperature ◽  
Tial Alloy ◽  
Tensile Fracture ◽  
Β Phase ◽  
Stable Element ◽  
Deformation Ability ◽  
Static Tensile ◽  
High Temperature Tensile

Study on the Ti-43Al-9V-0.3Y alloys forged microstructure, which added a large amount of β phase stable element. The influence on the mechanical properties and synusia cluster refinement about β phase is analyzed. The test of material static tensile at 700 °C and room temperature is conducted. The results show that the V elements urges the grain size α2 and β phase formation, β phase can inhibit α grain growth effectively. At the same time, its deformation ability can increase the high temperature plastic of the material. Experiments show that the main form of alloy tensile fracture at room temperature was intergranular fracture. Hole proliferation and communicated with each other through layers of crack is the main characteristics of high temperature tensile fracture of the alloy.

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