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A Study of the Influence of Multi-component Alloying on Oxidation Resistance of γ-TiAl Based Alloy

Author: LiDan
Tutor: ZhangGuoYing
School: Shenyang Normal
Course: Materials Physics and Chemistry
Keywords: First-principles calculations γ-TiAl alloy Oxidation resistance Vacancy formation energy Surface adsorption
CLC: TG132.32
Type: Master's thesis
Year: 2011
Downloads: 96
Quote: 0
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Abstract


γ-TiAl together compared with conventional titanium alloys and superalloys has a low density , good creep resistance , temperature up to 750-900 ° C than the advantages of strength and modulus , and therefore most promising as the hot parts of the aero-engine materials. However, the lack of capacity of high-temperature oxidation limits its application as a high temperature structural materials . To further enhance the titanium aluminum alloy high temperature oxidation resistance and corrosion resistance , this paper on the study of a variety of elements in Materials Studio software module based on the density functional theory (DFT) plane wave pseudopotential method (CASTEP) doped high-temperature oxidation of γ-TiAl the impact study found that : 1) adding alloying elements to reduce the Al vacancy formation energy , increase the vacancy formation energy of Ti to promote the diffusion of Al to the surface . Alloying elements such that the Ti enhanced interaction with other atoms , and weaken the interaction between Al and other atoms , and also promote the diffusion of A1 to the surface . A1203 A1 to the surface diffusion formed a dense oxide film , to improve the oxidation resistance of the γ-TiAl alloy . 2 ) oxidation of the γ-TiAl exist simultaneously inside and outside the oxide . Reducing the the O ion concentration in the γ-TiAl alloy elements , thereby reducing the speed of the internal oxidation . Doped alloy elements can be enhanced O and Ti , A1, and other alloying element interactions , to some extent, hindered the diffusion of oxygen , reduces the oxidation rate of the γ-TiAl alloy , to improve the antioxidant of γ-TiAl . 3) Oxygen is adsorbed on the surface of the γ-TiAl based alloy surface is chemical adsorption, co - doping of Nb and Si , so that adsorption is more prone . γ-TiAl alloy surface oxygen with Al and Ti exist between the role of covalent and ionic bonds . Adsorbed oxygen with Al -covalent interactions than with Ti strong , but the role of Al in an ionic bond is weak , but the overall effect difference is not large , which makes the oxidation of the TiAl intermetallic compound , it is possible to generate both Ti02 and A1203 . Si directly oxidized Si02 and A1203 layers together impede the conduct of the internal oxidation with oxygen . № , co-doped Si , Nb main function in the matrix , Si works mainly on the surface , the two effects can be superimposed , i.e. of Nb , Si doped so that the γ-TiAl alloy having a higher resistance to oxidation than added separately properties.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Special physical properties of alloys > Special thermal properties of alloys > Melting point alloys , refractory alloy , high temperature alloys
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