Structural and microstructural phase evolution during mechano-synthesis of nanocrystalline/amorphous CuAlMn alloy powders

• The formation of Cu solid solution was confirmed at short milling intervals.
• The austenite-to-martensite (2H) transformation and amorphization occurred by MA.
• Partial amorphization of 2H and amorphous phase crystallization happened during MA.
• At the end of milling, the transformation of L21-to-2H martensite occurred.
• By MA, the particles size was increased, then reduced, and afterward re-increased.

The formation mechanism of Cu–11.5Al–4Mn alloys by mechanical alloying (MA) of pure elemental powders was investigated. During milling, the powder sampling was conducted at predetermined intervals from 1 h to 96 h. The quantitative phase analyses were done by X-ray diffraction and the particles size and morphology were studied by scanning electron microscopy. Furthermore, the microstructure investigation and phase identification were done by transmission electron microscopy. Concerning the results, the nanocrystalline Cu solid solution were formed at short milling times and, by milling evolution, the austenite-to-martensite (2H) phase transformation occurred. Moreover, the formation of considerable amount of amorphous phase and its partial transformation to crystalline phases during the milling process were revealed. It was also found that, by milling development, the powder morphology changes from lamellar to semi-spherical and their size initially increases, then reduces and afterward re-increases.

Mechano-synthesis of nanocrystalline/amorphous Cu–11.5Al–4Mn shape memory alloys in the powder form: Cu solid solution formation, austenite-to-martensite (2H) transformation, amorphous phase formation, mechano-crystallization of the amorphous phase, and L21-to-2H transformation during the process.Figure optionsDownload as PowerPoint slide