Morphological and microstructural characterisation of low-alloying Fe powder obtained by mechanical attrition

Mechanical alloying (MA) has been used successfully to produce nonequilibrium microstructures with a high degree of homogeneity. In the present work iron powder (grade ASC 100.29, Hoganas, Sweden) were mixed with 8 wt.% of Ni-Cu prealloyed powders. MA was performed in an Ar atmosphere at room temperature at different milling times using a high-energy attrition ball-milling. Morphological and microstructural evolution of powders was characterised through scanning electron microscopy and X-ray diffractometry. Apparent density measurements of powders were made too. The morphological studies reveal three stages in the milling process. In the first stage, the particle deformation changes the irregular form of the as-received powder to flattened morphology and the apparent density decrease. In the second stage, the powder is enough deformed and hardened and the fracture process reduces the particle size. The apparent density increases due to the better packing of the particles. With continuous milling, the system reaches a steady state and the apparent density tends to a constant value. On the other hand, in X-ray diffraction patterns it can be observed a line broadening due to the refinement of the crystalline size and an increase in atomic level strain. The contribution of this two parameters were separated according to the Williamson-Hall method. (C) 2003 Elsevier B.V. All rights reserved.