A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young’s modulus, and Poisson’s ratio for ideal polycrystalline TiSi2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young’s modulus for single crystal TiSi2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the ...

Density functional theory for calculation of elastic properties of orthorhombic crystals: Application to TiSi2

Elastic constants of binary Mg compounds from first-principles calculations

Enthalpies of formation of magnesium compounds from first-principles calculations

Materials that are solid at high temperatures are in demand for high-temperature structural applications, and materials that have high values of strength-to-weight and stiffness-to-weight are desired for aircraft and space applications. Basic properties that are insensitive to processing history can be used to provide a preliminary ranking of single-phase substances. A compilation is presented of 293 intermetallic compounds (or metal-metalloid compounds) that melt at T ⩾ 1500° C. By displaying the data by crystal structure on plots ofT
m against the specific gravity ϱ candidates for optimum specific strength and specific stiffness can be recognized for materials that are likely to have similar plastic properties.

High-strength, high-temperature intermetallic compounds

Elastic properties of C40 transition metal disilicides

Elastic constants versus melting temperature in metals

Basic principles for selecting phases for high temperature metal matrix composites: interfacial considerations

A copper alloy dispersion strengthened by TiN was prepared by external nitridation in combination with mechanical alloying. After mechanical alloying pure Cu and Ti powders, a Cu-3wt.%Ti solid solution was formed. These powders were nitrided at 1073 K, resulting in a TiN layer on the surface of the copper powders. Further mechanical alloying was very efficient in breaking down the TiN surface layers. A very fine uniform distribution of nanosized TiN was obtained. The resulting copper alloy had a grain size of about 150 nm in diameter after annealing at 1173 K in vacuum for 5.4 ks, and showed a very high room temperature hardness value of 251 kg mm −2 which was independent of annealing temperature below 1173 K.

Preparation of Cu-TiN alloy by external nitridation in combination with mechanical alloying

In this study metal matrix composites were fabricated by nitridation of solute-rich NbTi and NbZr alloys to form large volumes of nitrides. Studies of the kinetics nitride formation and of the nature of the matrix-nitride interface were carried out. Nb-47wt%Ti and Nb-47wt.%Zr alloys were nitrided for different times and temperatures to nitride preferentially the solute phases into Ti- and Zr-rich nitrides. X-ray diffraction analysis confirmed the formation of the nitrides in the Nb solid solution matrix, and microhardness measurements explicitly indicated the hardening effect to be due to the formation of the nitrides. Orientation relationships were obtained between the matrix and the nitrides, but the habit planes were not defined.

M.E. Fine

Papers

Elastic constants versus melting temperature in metals

Basic principles for selecting phases for high temperature metal matrix composites: interfacial considerations

Preparation of Cu-TiN alloy by external nitridation in combination with mechanical alloying

Nitridation of niobium alloys: interface effects