Fabrication of a bulk icosahedral material through mechanical alloying of the powder mixture Ti_41.5Zr_41.5Ni₁₇

A bulk material that consists of the stable icosahedral phases (I-phases) in the Ti-Zr-Ni system has been fabricated in a hot press using mechanically alloyed (MA) powders. Considerable amounts of amorphous phase and nanocrystals are formed after MA for more than 30 h in the mixture of elemental powders (Ti, Zr, Ni) with the overall composition of Ti_41.5Zr_41.5Ni₁₇. The amorphous phase transforms into the I-phase in the temperature range of 573-673 K during continuous heating in differential scanning calorimetry (DSC) with the heating rate of 40 K/min. The powders MA for 40 h are hot-pressed for 2 h at 873 K under the applied pressure of 900 MPa to form a bulk I-phase material. The evolution of the Vickers microhardness has been examined in the load range of 0.5-10 N. The indentation size effect is accompanied by a modification of the fracture pattern. At a low value of the load, no crack is observed. As the load increases, the first cracks observed around the indenter are lateral cracks, and then radial cracks are found for load larger than 1 N.