The effect of the gas atmosphere on the response of the Al 86Ni 6Y 4.5Co 2La 1.5 metallic glass powder to heating

The response of nitrogen gas-atomised fully amorphous Al86Ni6Y4.5Co2La1.5 powder (<25 mu m) to heating in nitrogen and argon from 5 K/min to 40 K/min was investigated using differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and nano-indentation. The powder showed noticeably lower glass transition temperature, crystallization onset temperature, and peak crystallization temperatures in nitrogen than in argon, particularly at heating rates of >= 30 K/min. The activation energy for the onset of crystallisation of the powder was determined to be 301.58 +/- 42.47 kJ/mol in nitrogen compared to 418.18 +/- 7.20 kJ/mol in argon. Experimental evidence confirmed the reaction between the amorphous Al86Ni6Y4.5Co2La1.5 powder and nitrogen at >= 360 degrees C or even from similar to 280 degrees C. The powder that crystallized in nitrogen exhibited slightly but consistently higher hardness and elastic modulus. These results are necessary to inform the selection of the sintering atmosphere and parameters for the fabrication of bulk metallic glass of Al86Ni6Y4.5Co2La1.5 from powder.