Production of nanostructure Zr–ZrCr₂–Cr composite via MA process and subsequent heat treatment

ABSTRACT

In this study, the nanophase ZrCr₂ intermetallic compound was produced by the mechanical alloying (MA) and subsequent heat treatment. The phase transformations, crystallite size, lattice strain, and stored energy were studied at different milling times. The results indicated that MA caused to form a nanocomposite of the Cr(Zr) and Zr(Cr) supersaturated solid solutions. After 32 h of milling, the stored energy of Cr-reach phase in the powder mixtures reached to about 7.407 kJ/mol. Also, the 32 h milled powders were heated up to 750°C by the differential thermal analysis in argon atmosphere which the XRD results of the heated powders revealed that the nanostructure ZrCr₂ intermetallic compound was formed in the Zr and Cr matrix. Indeed, MA reduced the formation temperature of the ZrCr₂ intermetallic phase from 1673 °C to 608 °C which confirmed that MA and subsequent heating is a proper technique at low temperatures. In addition, a kinetics analysis implied that the Johnson-Mehl-Avrami (JMA) model can explain the kinetics formation of ZrCr₂ phase during the heat treatment which confirmed that the dominant mechanism of the intermetallic phase formation was the process controlled by the volume diffusion phenomenon, so that the nuclei grow in three dimensions of space.

KEYWORDS:

• MA
• heating
• transformations
• powder
• ZrCr₂
• nanophase
• composite
• kinetics