scholarly journals The Difference of Lamellar Structure Formation between Ti-45Al-5.4V-3.6Nb-Y Alloy and Ti-44Al-4Nb-4V-0.3Mo-Y Alloy

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 566
Author(s):  
Jianchao Han ◽  
Shuzhi Zhang ◽  
Changjiang Zhang ◽  
Fantao Kong ◽  
Yuyong Chen ◽  
...  
Keyword(s):  
Structure Formation ◽  
Phase Field ◽  
Lamellar Structure ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Common Factor ◽  
Β Phase ◽  
The Common ◽  
The Difference ◽  
Stabilizing Element

In this study, the effect factors on the formation of lamellar structure for Ti-45Al-5.4V-3.6Nb-Y alloy and Ti-44Al-4Nb-4V-0.3Mo-Y alloy is discussed in detail. During heat treatment in different procedures, temperature was the common factor influencing the formation of lamellar structures of Ti-45Al-5.4V-3.6Nb-Y and Ti-44Al-4Nb-4V-0.3Mo-Y alloys. In the range of 1230 °C and 1300 °C, the volume fraction of lamellar structure in Ti-45Al-5.4V-3.6Nb-Y alloy was proportional to the annealing temperature. However, between 1210 °C and 1260 °C, the volume fraction of lamellar structure in Ti-44Al-4Nb-4V-0.3Mo-Y alloy deceased when temperature was located in the α + γ + β triple phase field and then increased when temperature was in the α + β binary phase field. Besides the influence of temperature, the lamellar structure formation of Ti-44Al-4Nb-4V-0.3Mo-Y alloy was also affected by the β-phase stabilizing element.

scholarly journals Effect of C Addition on as-Cast Microstructures of High Nb Containing TiAl Alloys

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1201 ◽  
Author(s):  
Liu ◽  
Zhang ◽  
Nan ◽  
Feng ◽  
Ding
Keyword(s):  
Lamellar Structure ◽  
Volume Fraction ◽  
Eutectic Structure ◽  
Carbon Addition ◽  
Tial Alloys ◽  
Β Phase ◽  
Graphite Mold ◽  
Mold Casting ◽  
The Matrix ◽  
High Level

Two high Nb-containing TiAl alloys, Ti46.6Al7.5Nb0.5Si0.2B (Alloy A) and Ti46.1Al7.4Nb5C0.5Si0.2B (Alloy B), were prepared by graphite mold casting. As-cast microstructures of the two alloys were characterized to clarify the effect of carbon addition. The results show that 5 at.% carbon addition can change the primary solidification phase from β phase to α phase. The as-cast microstructure of Alloy A consists of a fully α2 + γ lamellar structure and interdendritic eutectic silicide with a volume fraction of 2.3%. However, in Alloy B, the lamellar structure only forms in the dendritic stem and the massive γ is observed in the interdendritic regions. Two types of carbides, Ti2AlC and TiC, are produced in Alloy B. A large number of randomly distributed primary Ti2AlC particles with volume fraction of 14.9% are observed in both the dendritic and interdendritic regions. Irregularly shaped TiC remains inside of the large Ti2AlC particle, suggesting TiC carbides transformed to Ti2AlC during cooling. The addition of carbon also changes the morphology of the silicides from a eutectic structure to a blocky structure in the massive γ matrix or at the interface of the Ti2AlC and the γ matrix. High level of niobium greatly increases the solid solution limit of carbon, since C content in the matrix is much higher than the solid solubility of that in the TiAl binary system. The hardness of the matrix increases from 325 HV to 917 HV caused by the addition of carbon.

scholarly journals Deformation Behavior of a β-Solidifying TiAl Alloy within β Phase Field and Its Effect on the β→α Transformation

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 605 ◽  
Author(s):  
Yi Chen ◽  
Liang Cheng ◽  
Guang Yang ◽  
Yalin Lu ◽  
Fengbo Han
Keyword(s):  
Phase Field ◽  
Deformation Behavior ◽  
Single Phase ◽  
Tial Alloy ◽  
Volume Fraction ◽  
Dislocation Creep ◽  
Strain Rates ◽  
Texture Intensity ◽  
Β Phase ◽  
Single Phase Field

In this study, the deformation behavior of a Ti-40Al-10V (at.%) alloy within β single phase field was examined by means of isothermal compression at 1300 °C under strain rates of 2 s−1, 0.2 s−1, and 0.02 s−1, as well as its effect on the subsequent β→α transformation. The results showed that the alloy behaved steady-state flow with dislocation creep as the predominant rate-controlling process. Dynamic recrystallization (DRX) evidently occurred during deformation, and its volume fraction was dramatically increased so that at the lowest strain rate (0.02 s−1), a full-DRX β structure was obtained. The preferentially dynamic migration of grain boundaries with <100> orientation was demonstrated to be the major DRX mechanism. The texture was characterized by a <100> + <111> double-fiber at 2 s−1, but gradually transformed into a simple rotated cube orientationunder 0.02 s−1, accompanied by a decreasing texture intensity. During the subsequent β→α transformation, two types of α morphology wereproduced with evident variant selection, namely, the Widmannstatten colony and martensitic laths. Texture simulation revealed that the α texture was solely determined by parent β texture, despite of the variant selections.

The Effects of Annealing Temperature on the Microstructure and Properties of Cold-Rolled 5083 Aluminum Alloy

2011 ◽  
Vol 217-218 ◽  
pp. 784-789
Author(s):  
Zhen Hai Bai ◽  
Bing Hui Luo
Keyword(s):  
Aqueous Solution ◽  
Tensile Strength ◽  
Aluminum Alloy ◽  
Annealing Temperature ◽  
Electrical Potential ◽  
Dry Air ◽  
Β Phase ◽  
Cold Rolled ◽  
The Difference ◽  
5083 Aluminum Alloy

The effects of annealing temperature on the strength and corrosin properties of cold-rolled 5083 aluminum alloy (ε=60%）were investigated. The results show that the tensile strength of the alloy decreases with rising annealing temperature. The alloy shows ductile cracking in dry air and brittle cracking in 3.5%NaCl aqueous solution. The alloy reserves the most positive electrical potential at 200°C, and low SCC susceptibility at 200、250°C when annealed, but reserves relative high SCC susceptibility at 100, 150,300 and 350°C, which can be attributed to the difference shape and distribution of β-phase annealed at different temperature.

Phase-Field Simulation of Lamellar Structure Formation in MoSi2/NbSi2 Duplex Silicide

2013 ◽  
Vol 1516 ◽  
pp. 309-315 ◽  
Author(s):  
Yuichiro Koizumi ◽  
Toshihiro Yamazaki ◽  
Akihiko Chiba ◽  
Koji Hagihara ◽  
Takayoshi Nakano ◽  
...  
Keyword(s):  
Structure Formation ◽  
Phase Field ◽  
Interfacial Energy ◽  
First Principles ◽  
Lamellar Structure ◽  
Lattice Misfit ◽  
First Principles Calculation ◽  
Cr Addition ◽  
Image Position ◽  
Habit Planes

ABSTRACTWe conducted phase-field simulations of microstructural evolution in C11b-MoSi2 / C40-NbSi2 dual phase alloy with and without Cr-addition to examine the factors responsible for the formation and stability of the lamellar structure on the basis of thermodynamics, micromechanics and first-principles calculations. The first principles calculation was used for evaluating the interfacial energy, segregation energy of solute Cr-atoms and lattice parameters of imaginary disilicides for estimating the effects of solute distribution on the lattice misfit. When both of lattice misfit and the anisotropy of interfacial energy is taken into account, a lamellar structure similar to that observed experimentally is formed. In the absence of Cr-addition, the straightness of lamellar structure decreased slightly. When an isotropic interfacial energy is assumed, lamellar structure is not formed. Instead, a microstructure with habit planes parallel to {1 0 $\bar 1$ 1} plane of C40-phase is formed. Thus, the anisotropy of interfacial energy is crucial for the lamellar structure formation rather than the elastic energy due to lattice misfit.

scholarly journals The Influences of Process Annealing Temperature on Microstructure and Mechanical Properties of near β High Strength Titanium Alloy Sheet

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1478 ◽  
Author(s):  
Zhaoxin Du ◽  
Yan Ma ◽  
Fei Liu ◽  
Ning Xu ◽  
Yanfei Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
Cold Rolling ◽  
Phase Field ◽  
Annealing Temperature ◽  
High Strength ◽  
Goss Texture ◽  
Β Phase ◽  
Cold Rolled ◽  
Process Annealing

The influences of process annealing temperature during cold rolling on microstructure and mechanical properties of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe near β high strength titanium alloy sheets have been investigated. Results showed that the alloy mainly included the deformation induced dislocation structures after cold rolling but no obvious band structure, twin crystal or martensite were observed in this work. The texture components, which were affected by process annealing, are mainly γ-fiber, α-fiber and weak Goss texture. The γ-fiber of alloy when process annealed at 780 °C (α/β phase field) is stronger than at 830 °C (β phase field), where the Goss texture of alloy with process annealing temperature of 830 °C is more obvious. Results of annealing heat treatments showed that the recrystallization of the cold rolled was basically completed in a relatively short time of 2 min at 750 °C for 2 min. The refinement of grain size led to a significant increase of plasticity compared to rolled alloy. Results of tensile testing of aged alloy display the excellent combination of strength and plasticity, and the cold rolled alloy with process annealed at α/β phase field exhibits the better mechanical properties than at β phase field.

Microstructural Difference between Unreinforced Canning of TC17 Alloy and the Matrix in SiCf/TC17 Composite Fabricated by HIP Process

2016 ◽  
Vol 849 ◽  
pp. 402-408
Author(s):  
Min Juan Wang ◽  
Hao Huang ◽  
Si Qing Li ◽  
Hu Li ◽  
Chuan Xie ◽  
...  
Keyword(s):  
Lamellar Structure ◽  
Hot Isostatic Pressing ◽  
Matrix Alloy ◽  
Carbon Layer ◽  
Sic Fiber ◽  
The Matrix ◽  
Transus Temperature ◽  
The Difference ◽  
Hip Process ◽  
Stabilizing Element

Continuous unidirectional SiCf/TC17 composite has been fabricated by hot isostatic pressing (HIP). After consolidation, the TC17 canning (the unreinforced ambient portion of the specimen) showed an equiaxed microstructure, whereas the matrix of SiCf/TC17 composite (deposited on the continuous SiC fibers by magnetron sputtering) exhibited a typical lamellar structure. In this work, the heat treatments under different condition, XRD, SEM and WDS have been employed to characterize and analyze the microstructural difference. The results indicated that the difference in β transus temperature (Tβ) between the canning and matrix of TC17 alloy induced the microstructural diversity. The introduction of C element (an intensive α stabilizing element) into the matrix alloy may be ascribed to the diffusion of carbon layer at the surface of SiC fiber. As a result, Tβ of matrix TC17 alloy increased to above 1000 °C, much higher than that of the canning TC17 alloy (890 °C). The investigation of microstructure difference reveals the microstructure evolution in SiCf/TC17 composite, which can provide an effective reference for following processing design.

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