Structural evolution of mechanically alloyed TiAl alloys

Suryanarayana, C.; Chen, Guo-Hao; Frefer, Abdulbaset; Froes, F. H.

doi:10.1016/0921-5093(92)90139-r

Cited by 75 publications

(25 citation statements)

References 21 publications

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Section: Resultsmentioning

confidence: 99%

“…Thus, it was confirmed that the corresponding new phase was a hcp Ti-Al solid solution. [9] Other features in Figure 2 are a broadening of the Ti-Al peaks and a decrease in the line intensity with increasing MA time.The XRD identification reveals two different manners for the formation of the TiC carbide phase and the Ti-Al solid-solution phase ( Fig. 1 and Fig.…”

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confidence: 99%

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Structural Evolution during Reactive Mechanical Milling of TiC/Ti‐Al Nanocomposites

Shen

2009

Adv Eng Mater

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High-energy Mechanical Alloying (MA) has been used successfully to produce numerous equilibrium or nonequilibrium alloy phases starting from blended elemental or pre-alloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. [1][2][3] MA, as a non-equilibrium, low temperature, and solid-state powder treatment process, involves repeated cold-welding, fracturing, and re-welding of powder particles in a high-energy ball mill.Titanium aluminides (TiAl) are of great importance for intermediate-temperature (600 to 850 8C) aerospace and power-generation applications because they offer significant weight savings over today's nickel-based superalloys. [4] Furthermore, TiAl alloys possess a unique combination of high specific strength, high elastic modulus, and excellent antioxidation capabilities. [5] However, the limited roomtemperature ductility and the decreased high-temperature strength are the most-significant impediments to broadening their practical applications. [6] In order to improve their ductility, recent research efforts have focused on the preparation of ultrafine grained nanocrystalline TiAl. [7] On the other hand, the synthesis of ceramic reinforced TiAl-matrix nanocomposites is an important consideration in improving their high-temperature performance. In particular, the preparation of in situ particulate-reinforced nanocomposites is regarded as the most-promising method. [8] The ultrafine particulates that are formed in situ are thermally stable and possess coherent and compatible interfaces with the matrix, thereby assuring that the composite system has enough strength to transfer stress.MA provides us with an innovative process of the in situ preparation of ceramic-particulate-reinforced nanocomposites materials. Ultrafine, nanometer-scaled grain sizes coupled with a uniform distribution of the reinforcing phases are expected to improve the obtainable mechanical properties of composites prepared by the MA route. Nevertheless, MA is a complex process and accordingly involves a large degree of uncertainty in obtaining the desired phases and microstructures. Significant experimental research is still required to study how the phases, microstructures, and compositions of MA-processed powder are evolved during ball milling. A theoretical understanding of the formation mechanisms behind the microstructural development of milled powders is also regarded as necessary.In this work, TiC/Ti-Al nanocomposite powders were synthesized in situ by MA of a mixture consisting of elemental Ti, Al, and graphite powder, with a nominal composition of Ti 50 Al 25 C 25 . The phase, microstructure, and composition transformations of the milled powders were characterized and reasonable mechanisms for the powder formation during the reactive MA process are proposed. Results and DiscussionThe X-ray diffraction (XRD) spectra of the starting elemental-powder mixture and the milled powders at different MA ti...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Structural Evolution during Reactive Mechanical Milling of TiC/Ti‐Al Nanocomposites

Shen

2009

Adv Eng Mater

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“…The anticipation in this case was that if the glassy powders could be consolidated to full density without crystallization, then it would be possible to overcome the limitation of section thickness imposed by the solidification route. A number of investigations were also undertaken to develop aluminides based on Ti, Ni, and Fe to determine whether these alloys in the nanostructured condition would exhibit more ductility [10][11][12][13][14][15]. Many of these investigations were not encouraging since the MA-processed nanostructured aluminide alloys did not show any improved ductility at room temperature.…”

Section: Past Developmentsmentioning

confidence: 99%

Recent Developments in Mechanical Alloying

Poole

Fischer

1994

Materials Technology

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Abstract. Mechanical alloying (MA) is a powder metallurgy processing technique that involves repeated cold welding, fracturing and rewelding of powder particles in a high-energy ball mill. Started in 1960 to produce oxide dispersion strengthened (ODS) nickel-based superalloys to obtain high strength both at room and elevated temperatures, this technique is now widely used to synthesize a variety of non-equilibrium alloys including solid solutions, intermetallics, and glassy alloys. Apart from the ODS alloys, the products of MA are now finding ever increasing and newer applications. The present article briefly summarizes the past achievements of MA followed by a discussion of the present activities. Three specific topics have been covered -nanocomposites, metallic glasses, and use of MA powder particles in metal combustion. The article concludes with an indication of the topics that need special attention in the near future.

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“…5) However, some researchers reported that a phase with fcc structure (TiN) might be formed while the milling was conducted under Ar atmosphere, due to the ineffective seal of the milling tools. [6][7][8][9] Additionally, TiC (fcc structure) was also obtained due to the decomposition of PCA's during mechanochemical synthesis of elemental Ti and Al powder mixture. 10,11) It is obvious now that nitride and carbide contamination phases are easily formed due to the inherent nature of Ti as a reactive metal.…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6][7][8][9][10][11] The effect of the milling parameters such as milling tools, different milling atmosphere, different combination of powders and the addition of different process control agent (PCA's), was widely investigated. Most of the results show that amorphization should be accomplished after long time milling under Ar atmosphere, which is in good accordance with the theoretical calculation.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Evaluation of Ordinary Attritor Milled Ti-Al Powders and Corresponding Thermal Sprayed Coatings

2006

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Ordinary attritor milling of elemental metallic powders under atmospheric condition was utilized to prepare desirable amount of powders for thermal spraying. The effect of different BPR (Ball to Powder weight Ratio) has been investigated in terms of nitridation during milling. To investigate the effect of heat treatment on the formation of dispersed phases, heat treatment to the powder was performed as well. Titanium aluminide coatings with carbonitride dispersed phases were successfully fabricated by low pressure plasma spraying. The hardness and specific wear of the coatings prepared by the powders with different milling conditions was measured so as to investigate the effect of the content of dispersed titanium based carbonitride phases. Experimental results show that the formation of dispersed carbonitride phases depends strongly on milling condition, irrespective of heat treated powders or thermal sprayed coatings, and directly affects the mechanical properties of the coatings. Compared with the phase composition of heated powders and corresponding thermal sprayed coatings, it seems that the temperature of processing the MA powders is also a decisive factor on the phase formation, especially carbonitride phases and oxide phase.

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Structural evolution of mechanically alloyed TiAl alloys

Cited by 75 publications

References 21 publications

Structural Evolution during Reactive Mechanical Milling of TiC/Ti‐Al Nanocomposites

Structural Evolution during Reactive Mechanical Milling of TiC/Ti‐Al Nanocomposites

Recent Developments in Mechanical Alloying

Preparation and Evaluation of Ordinary Attritor Milled Ti-Al Powders and Corresponding Thermal Sprayed Coatings

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