Titanium Aluminide Intermetallic Compounds are a small group of materials that can be used at high temperature structures where the specific strength (strength to density ratio) and specific stiffness (elastic modulus to density ratio) are very important. In this study, some output characteristics of electrical discharge machining (EDM) process; including material removal rate (MRR), surface roughness and topography are investigated for this material. The DOE method of full factorial is used for planning the machining tests that two main input parameters of pulse current and pulse on time are changed in five and four different levels, respectively and other input machining parameters are kept constant during tests. The results show that in lower currents (3 and 6 A), despite the increase in pulse time, there is no significant change in MRR and the MRR for these two currents is negligible, indicating that finishing process of Titanium Aluminide is difficult and time consuming, but there is no such situation in more currents (12, 24 and 64 A) and the roughing process of this material is optimally carried out. For the currents above the 24 A, the gradient of MRR increase, is decreased because of arc appearance. In the states of higher electrical currents, the lengths of cracks on the machined surface are increased and the widths of cracks are growing. While arc is occurred for the higher electrical discharge energy, the surface roughness and topography are intensively different from the other current and pulse on time conditions.

In this study, three series of electrical discharge machining experiments were carried out on γ-TiAl Intermetallic. In the first series, by changing pulse current and pulse on time in EDM process and in the second series by changing the size and concentration of aluminum powder particles mixed in dielectric fluid, output characteristics including material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) are evaluated. In the third series of machining experiments, after determination of the optimum size and concentration of aluminum particles, current and pulse on time, are changed at levels as exactly the same levels in powder-free tests and MRR is evaluated. Finally, MRR of the EDM and optimum PMEDM processes, are compared. By increasing the aluminum particles concentration, TWR and SR will be decreased to an optimal level and then will be increased. For particle size of 2 μ m and 20 μ m, by increasing the aluminum powder concentration, MRR increases at first and then decreases, while for particle size of 63μ m, by increasing powder concentration, MRR decreases. The minimum and maximum increment of MRR in optimum PMEDM condition compared with EDM mode was 32% and 88%, respectively. With increase of electrical discharge energy, the addition of aluminum powder has less effect on increase of sparking frequency and consequently the MRR.

In this article, an attempt was made to investigate the effect of the addition of silicon on the Titanium Aluminide Compound formation from TiO2 and Al raw materials. Silicon has a eutectic with aluminum and can reduce its melting temperature, which can have effective impact on the formation of Titanium Aluminide Compounds. On the other hand, due to the production of Ti5Si3 Compound, it can be effective in increasing the oxidation resistance of Compounds and composites containing Titanium Aluminide. With this aim in mind, the present paper has strove to determine the impact of this element on the formation of Titanium Aluminides and the type of Titanium silicide phases by adding different amounts of silicon to TiO2 and Al raw materials. The key findings emerged, showed that when silicon is added to the system in small amounts (0.1), it not only does not have a positive effect on the reactions, it also prevents the formation of Titanium Aluminide Compounds, but with an increase in its percentage (0.28), it also causes the formation of these Titanium Aluminide Compounds and leads to the formation of Ti5Si3 phase. This phase changes from a discrete morphology to a continuous state as the percentage of silicon increases (0.6). With a further increase in the amount of silicon (1), the TiSi2 phase is formed, which is dispersed throughout the sample with a string-like structure.

Titanium Aluminides have received much attention due to their suitable properties such as lightness, maintaining strength at high temperatures, and resistance to corrosion and oxidation. Therefore, Titanium Aluminides and their composite play a key role in the industry, especially in urban transportation and aviation industries. The melting of aluminum is recognized as the first step of the Titanium Aluminide formation process from elemental powders or raw materials of TiO2 and Al. Facilitating the aluminum smelting could be a contributing factor to accelerating the Titanium Aluminide-generating procedure. Selecting copper as an agent to reduce the melting point of aluminum is based on the binary phase diagram of Al-Cu in which a eutectic transformation is obvious. Different molar ratios of copper were added to the raw materials of aluminum and titania. Then the resulting compressed powder samples were subjected to heat treatment. It was found that up to a certain molar ratio, copper could reduce aluminum's melting temperature and promote the formation of Titanium Aluminide Intermetallic Compounds. The optimal amount of copper (0.2) has also greatly contributed to the uniformity and homogeneity of the composite structure. In general, in this research, the effect of copper on the production of Titanium Aluminide has been discussed both theoretically and practically.

Combustion synthesis is a special thermophysico-chemical process applied for production of Intermetallic Compounds. In the present work, a reaction–diffusion numerical model was developed to analyze the combustion synthesis of Aluminide Intermetallics by self-propagating high-temperature synthesis process. In order to verify the reliability of the numerical model, an experimental setup was designed and used to perform the combustion synthesis of nickel and Titanium Aluminides. The developed model was further used to determine the temperature history of a powder mixture compact during self-propagating high-temperature synthesis. The effect of compact relative density on combustion temperature and wave propagation velocity was also studied.

g-TiAl Intermetallic alloy have a good potential for use as biomaterial, due to its good corrosion resistance. In this paper, two fundamental electrochemical techniques namely electrochemical impedance spectroscopy and potentiodynamic anodic polarization were used to evaluate the corrosion performance of g-TiAl in Ringer's solution. Surface modification treatments were employed with the purpose of improving corrosion resistance. The samples were oxidized at 550°C in air for 1 h. The results show that oxidized Ti-47Al-2Cr has much better corrosion resistant in Ringer’s solution. The presence of the oxide layer formed with the surface treatments increased their corrosion resistance. The low values of corrosion rate, and the high values for corrosion potential (Ecorr) and polarization resistance (Rp) obtained experimentally implies that g-TiAl can be competitively considered as an alternative metallic biomaterial.

In this research, the nickel oxide was dissolved in cryolite at temperatures of 880, 940 and 1000oC. In order to reduce the nickel oxide, aluminum was added to the salt. Simultaneously the nickel oxide was reduced and Al3Ni2 Intermetallic Compound was formed. In the duration intervals of 2.5-40 minutes samples of the salt and metallic phases were taken. The variation of the nickel content in metallic and salt samples was determined by the AAS. The results indicate that increasing the temperature and duration has a positive effect on the reduction process and Al3Ni2 Intermetallic Compound formation. The nickel content in the metallic sample has its highest amount at 1000oC in 10 minutes. Furthermore, practical results of the studies of nickel content variations in metallic and salt samples confirm the data obtained from theoretical calculations.

Ni and Al elemental powder mixture with composition Ni75Al25 were mechanically alloyed in a planetary ball mill under different conditions. The structural changes of powder particles were studied by x-ray diffractometry and scanning electron microscopy. Mechanical alloying for ≈ 10h resulted in a solid solution of Al in Ni which transformed to Ni3Al Intermetallic Compound with nanocrystalline structure after≈ 20h of milling time. Decreasing ball-to-powder weight ratio or rotation speed of mill, drastically retarded the formation of Ni3Al phase. However, decreasing size of balls, while the balls-to-powder weight ratio remained constant, did not change mechanical alloying process significantly.      

Reactive sintering is a kind of combustion synthesis processes for synthesize of new materials. In this research, the mentioned process was used for production of Titanium Aluminide/alumina composite from starting materials of Titanium dioxide and aluminum. According to the obtained results, composite particles including TiO2/Al with a size around 100 nm can be produced. Densification of produced powders via cold isostatic pressing machine following by reaction sintering lead to produce a composite body consisting Titanium aluminids and alumina.

KRH process is a new way for producing Titanium Aluminide Intermetallic Compound on the basis of a complex reaction between tio2,  Al, Ca and kclo4 reacting materials. In this study ,the occurred phenomena in different temperature regions were investigated and a temperature region which the reaction had a self-propagating behavior was determined by temperature measurement in the reaction vessel and DTA analysis. It was found that the process was ignited via the reaction between kclo4 and Ca. A self propagating reaction started after the ignition of process.