Study of Refined Microstructures after Two-Step Heat Treatments by Means of EBSD Technique on γ-TiAl Alloys

In this work, significant modification of the microstructure of a rolled Ti-45Al-5Nb (at.%) alloy has been achieved by a two-step heat treatment. A combination of high cooling rates for the first step of the treatments with a subsequent annealing at high temperatures, results in refined microstructures where substantial discontinuous coarsening seems to play an important role for the grain refinement. In order to fully understand the transformation mechanisms responsible for such a refinement, Electron Back Scattered Diffraction (EBSD) technique has been extensively used. In particular, a study of orientation relationships between the phases which are present in the transformed microstructures, was performed by this technique. Besides discontinuous coarsening process, the obtained results also suggest that a modified discontinuous coarsening mechanism is operative, in order to justify the formation of novel microstructures, whose development could not be explained by the classical discontinuous coarsening.

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Phases transformation textures in steels

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2004120015 ◽

2004 ◽

Vol 120 ◽

pp. 137-144

Author(s):

C. Cabus ◽

H. Regle ◽

B. Bacroix

Keyword(s):

Phase Transformation ◽

Thermomechanical Processing ◽

Texture Evolution ◽

Residual Austenite ◽

Carbon Steels ◽

Low Carbon ◽

Orientation Relationships ◽

Cold Rolling And Annealing ◽

Transformation Mechanisms ◽

Ebsd Technique

Low-carbon steels used for deep-drawability applications have properties which depend greatly on their crystallographic texture. It is therefore important to control the texture evolution during the thermomechanical processing. Until recently, little attention has been paid on the understanding of the textures formation after hot-rolling, which are produced by phase transformation, although it is recognised that they have an effect on the development of the texture in the further process (cold rolling and annealing). Indeed, one of the main difficulties consists in the measurement of texture above ambient temperature, in the austenite range. In the present work, EBSD technique is employed on a low-C steel and a method is proposed to determine local austenite orientation thanks to martensitic one, even if there is no residual austenite in the steel. The orientation relationships between the austenite phase and each of its product phases, here martensite and polygonal ferrite, are analysed and compared. Common Kurdjumov Sachs variants are detected for both phases. Variations in the intensities of these variants are also detected and could be due to the different phase transformation mechanisms, diffusion or shear.

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Effect of Two-step Heat Treatment Processes on the Formation of Protein Particles and Oil Droplets in Soymilk

Food Science and Technology Research ◽

10.3136/fstr.26.445 ◽

2020 ◽

Vol 26 (3) ◽

pp. 445-450

Author(s):

Makoto Shimoyamada ◽

Hironori Shikano ◽

Shingo Mogami ◽

Makoto Kanauchi ◽

Hayato Masuda ◽

...

Keyword(s):

Heat Treatment ◽

Oil Droplets ◽

Treatment Processes ◽

Protein Particles ◽

Step Heat Treatment

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Effect of Heat Treatment on the Microstructure and Property of TiAl Alloys Prepared by Gas Atomization Powders

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.497 ◽

2013 ◽

Vol 747-748 ◽

pp. 497-501

Author(s):

Na Liu ◽

Zhou Li ◽

Guo Qing Zhang ◽

Hua Yuan ◽

Wen Yong Xu ◽

...

Keyword(s):

Heat Treatment ◽

Heat Treatment Temperature ◽

Tial Alloy ◽

Lamellar Microstructure ◽

Treatment Temperature ◽

Gas Atomization ◽

Thermally Induced ◽

Heat Treated ◽

Fine Duplex ◽

Step Heat Treatment

Powder metallurgical TiAl alloy was fabricated by gas atomization powders, and the effect of heat treatment temperature on the microstructure evolution and room tensile properties of PM TiAl alloy was investigated. The uniform fine duplex microstructure was formed in PM TiAl based alloy after being heat treated at 1250/2h followed by furnace cooling (FC)+ 900/6h (FC). When the first step heat treatment temperature was improved to 1360/1h, the near lamellar microstructure was achieved. The ductility of the alloy after heat treatment improved markedly to 1.2% and 0.6%, but the tensile strength decreased to 570MPa and 600MPa compared to 655MPa of as-HIP TiAl alloy. Post heat treatment at the higher temperature in the alpha plus gamma field would regenerate thermally induced porosity (TIP).

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The orientation relationships of nanobelt-like Si2Hf precipitates in an Al–Si–Mg–Hf alloy

Journal of Applied Crystallography ◽

10.1107/s160057671600933x ◽

2016 ◽

Vol 49 (4) ◽

pp. 1223-1230 ◽

Cited By ~ 6

Author(s):

Xueli Wang ◽

Huilan Huang ◽

Xinfu Gu ◽

Yanjun Li ◽

Zhihong Jia ◽

...

Keyword(s):

Electron Microscopy ◽

Heat Treatment ◽

Coincident Site Lattice ◽

Orthorhombic Structure ◽

Orientation Relationships ◽

Lattice Distribution ◽

Site Lattice ◽

Transmission Electron ◽

Habit Planes ◽

Al Matrix

The orientation relationships (ORs) between the Al matrix and Si2Hf precipitates with an orthorhombic structure in an Al–Si–Mg–Hf alloy after heat treatment at 833 K for 20 h were investigated by transmission electron microscopy and electron diffraction. Four ORs are identified as (100)Al||(010)p, (0\overline {1}1)Al||(101)pand [011]Al||[\overline {1}01]p; (11\overline {1})Al||(010)pand [011]Al||[\overline {1}01]p; (12\overline {1})Al||(010)p, (101)Al||(100)pand [1\overline {11}]Al||[001]p; (\overline {11}1)Al||(010)pand [112]Al||[\overline {1}01]p. The habit planes of these four ORs are rationalized by the fraction of good atomic matching sites at the interface. In addition, the formation of Si2Hf precipitates with a nanobelt-like morphology is interpreted on the basis of the near-coincident site lattice distribution.

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Additive Manufacturing of Ti-Based Intermetallic Alloys: A Review and Conceptualization of a Next-Generation Machine

Materials ◽

10.3390/ma14154317 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4317

Author(s):

Thywill Cephas Dzogbewu ◽

Willie Bouwer du Preez

Keyword(s):

Heat Treatment ◽

High Temperature ◽

Additive Manufacturing ◽

Complex Geometries ◽

Intermetallic Alloys ◽

Tial Alloys ◽

Conventional Methods ◽

Manufacturing Technologies ◽

In Situ Heat Treatment

TiAl-based intermetallic alloys have come to the fore as the preferred alloys for high-temperature applications. Conventional methods (casting, forging, sheet forming, extrusion, etc.) have been applied to produce TiAl intermetallic alloys. However, the inherent limitations of conventional methods do not permit the production of the TiAl alloys with intricate geometries. Additive manufacturing technologies such as electron beam melting (EBM) and laser powder bed fusion (LPBF), were used to produce TiAl alloys with complex geometries. EBM technology can produce crack-free TiAl components but lacks geometrical accuracy. LPBF technology has great geometrical precision that could be used to produce TiAl alloys with tailored complex geometries, but cannot produce crack-free TiAl components. To satisfy the current industrial requirement of producing crack-free TiAl alloys with tailored geometries, the paper proposes a new heating model for the LPBF manufacturing process. The model could maintain even temperature between the solidified and subsequent layers, reducing temperature gradients (residual stress), which could eliminate crack formation. The new conceptualized model also opens a window for in situ heat treatment of the built samples to obtain the desired TiAl (γ-phase) and Ti3Al (α2-phase) intermetallic phases for high-temperature operations. In situ heat treatment would also improve the homogeneity of the microstructure of LPBF manufactured samples.

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The Effect of Two-Step Heat Treatment Parameters on Microstructure and Mechanical Properties of 42SiMn Steel

Metals ◽

10.3390/met7120537 ◽

2017 ◽

Vol 7 (12) ◽

pp. 537 ◽

Cited By ~ 4

Author(s):

Ludmila Kučerová

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Microstructure And Mechanical Properties ◽

Step Heat Treatment

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Preparation of aluminum nitride granules by a two-step heat treatment method

Advanced Powder Technology ◽

10.1016/j.apt.2018.01.001 ◽

2018 ◽

Vol 29 (4) ◽

pp. 849-854 ◽

Cited By ~ 5

Author(s):

Kuan-Ting Lai ◽

Cheng-Hung Shih ◽

Chun-Te Wu ◽

Min-Yu Yang ◽

Chi-Shiung Hsi

Keyword(s):

Heat Treatment ◽

Aluminum Nitride ◽

Treatment Method ◽

Step Heat Treatment ◽

Heat Treatment Method

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

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.258.501 ◽

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.

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