The ductility and strength of Fe−Cr−Al alloys

Metal Science and Heat Treatment -     

Properties and heat treatment of Ti−Nb and Ti−Nb−Al alloys

Metal Science and Heat Treatment -     

Effect of microalloying on the structure and properties of alloys in the Al−Si−Cu system

Conclusions  

On the physicochemical mechanism of modification of Al−Si alloys

Conclusions  

Ti−V−Cr BCC alloys system with high protium content

This paper aims to study the relationship between the protium absorption properties and alloy composition of Ti−V−Cr alloys. We studied the effects of composition of the alloys and the heat-treatment on the protium absorption-desorption properties of Ti−V−Cr alloys, and found that Ti−35V−40Cr alloys show 2.6 mass% protium capacity. The plateau pressure of the alloys increased with decreasing lattice constants, resulting from increasing Cr content. The main phase of the samples containing more than 15%V was a BCC phase in the cast state. These BCC phase alloys exhibited 2.4 mass% protium. It was also found that the heat-treatment was effective in stabilizing a BCC structure in Ti−V−Cr alloys with low V content. The alloy yields the high capacity of 3.0 mass% protium capacity, which will be the highest value at 313 K reported so far. The alloy will be promising since it contains a low amount of the expensive V element. This article based on a presentation made in the symposium “The 2nd KIM-JIM Joint Symposium: Hydrogen Absorbing Materials”, held at Hanyang University, Seoul, Korea, October 27–28 under the auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

Relation between phase transformations and mechanical properties of alloys in the Ti−Al−W−Zr system

Conclusions  

Effect of thermal cycling on the structure of quenched alloys of the Ti−Ta−Nb system

Conclusion In alloys of the system Ti–Na–Nb, it is possible to obtain -martensite in which both reversible and irreversible phase transformations occur upon thermal cycling. Reversible phase transformations are observed preferentially in alloys where tantalum atoms predominate among th dopants, and the -martensite has a certain degree of rhombic distortion of the crystal lattice.A. A. Baikov Institute of Metallurgy, NIID. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 25–27, March 1992.     

Inelastic effects in ordering of Fe−Al alloys

The effects of the aluminum content in binary b.c.c. alloys of the Fe−Al system and of the processes of ordering in the substitutional solid solution on the activation energy of diffusion of carbon atoms and magnitomechanical dissipation of the energy of mechanical vibrations are studied. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 3–9, April, 1998.     

Solidification structures of Ti–Al–Cr alloys

Phase transformations in the ternary Ti–Al–Cr alloy system have been studied by combining preliminary phase equilibria calculations and microstructural studies of a number of model alloys. The results have contributed to a better understanding of phase equilibria in the Ti–Al–Cr alloy system above 1273 K. A liquid surface projection has been tentatively proposed. Micro-twins have been observed in the monolithic γ phase within a B2 matrix. This supports a previously proposed mechanism for the formation of such a structure in a B2 matrix. The results also suggest that there is no representative orientation relationship between γ and the Ti(Cr,Al)₂ Laves phase. The L1₂ τ phase can be in direct equilibrium with the liquid phase. The ω phase stability has also been studied. The stability of the ω phase is attributed to the electron density of the prior B2 phase. This leads to changes in the effective heat of formation of the ω structure, as concluded from total energy LMTO calculations.     

Indirect evaluation of the long-term oxidation properties of Al−21Ti−23Cr and Al−37Ti−12Cr coating materials for TiAl alloy

The most pertinent coating materials in the Al−Ti−Cr alloy system to improve the high temperature oxidation resistance of a TiAl alloy, with respect to oxidation properties, resistance to thermal stress, and chemical compatibility, are the two-phase alloys of Al−21Ti−23Cr (L1₂+Cr₂Al) and Al−37Ti−12Cr (γ+TiAlCr). In this study, cyclic oxidation tests at 1000 °C and 1200 °C were performed for the specimens coated with both materials of 10 im thickness. Furthermore, breakaway oxidation caused by the formation of a rutile TiO₂ scale was observed, though both bulk alloys showed very stable oxidation behavior. This phenomenon was resulted from the depleted Al content in the coating layer due to Al₂O₃ oxide growth and interdiffusion with the substrate. Considering the decrease of Al content due to oxide growth, the Al−21Ti−23Cr coating with the initial higher Al content was more effective for long-term oxidation protection of the TiAl alloy. On the other hand, when the Al content changes due to the interdiffusion with the substrate, the Al−37Ti−12Cr coating with a smaller compositional gradient with the TiAl substrate was more effective than the Al−21Ti−23Cr coating. Cyclic oxidation tests at 1000 °C and 1200 °C confirmed that for the longer lifetime of coating materials the initial Al content was more important than the smaller compositional gradient with the substrate. Consequently, the Al−21Ti−23Cr coating was considered as more effective one for the long-term oxidation resistance of TiAl alloys.     

Solidification microstructures and carbides morphology in rapidly solidified Fe−Al−Cr−C alloys

The combined effects of alloying additions and heat treatment on the evolution and development of the microstructures of Fe₃Al-based Fe−Al−Cr−C alloys produced by melt suction processing have been examined. Particular emphasis has been placed on the distribution and morphology of carbides in rapidly solidified Fe₃Al-based intermetallics. The results suggest that the formation of intrinsically hard and brittle Fe₃AlC and Cr₇C₃ type carbides depends on the alloying content. These carbides tend to form preferentially along the grain boundaries where more continuous and coarse networks are observed, especially for alloys having higher Cr and C content. These networks are fragmented as a result of heat treatment at 1200 °C and subsequent air cooling and quenching.