EXAFS And XRD Measurement On Microstructures Of Mechanically Alloyed Fe₆₀Ni₄₀ Nano System

Fe-Ni alloys prepared by mechanical alloying(MA) are widely used because of their excellent stability and magnetic capability. X Ray Diffraction and Extend X-ray Absorption Fine Structure can be applied to analyze and test the structures of the MA products. XRD is a reliable way to study the long-range structure of crystal, and EXAFS is a powerful method to ascertain the structure of atom's local environment.During MA, the powder sample can be introduced lattice strain by high-energy milling, which can be renovated by rapid annealing. In this paper, Fe-Ni alloys are prepared by mechanical alloying and rapid annealing, and the EXAFS and XRD techniques are used to study the Microstructures of Mechanically alloyed Fe60Ni40 System before and after being annealed. The results indicate that at the initial MA stage milling for 5 hours,the powder Fe60Ni40 mixture still maintains original bcc and fcc structure. After being milled for 10 hours,a-Fe phase in the sample almost completely disappears, only with the fcc phase,disorder factor a of the Fe and Ni atom is larger than that of before milling, most of Fe atoms change from a bcc stucture to a fcc structure. When the milling time increases to 40 hours,disorder factor a of the Fe and Ni atom continues to increase, the coordination distance R and coordination number N of Fe atoms are equal to those of Ni atoms. So the sample Fe60Ni40(40h) is a homogenous solid solution. After being rapid annealed, the intensity of XRD diffraction peaks and atom coordination peaks of the sample distinctly strengthens, and atom disorder factor decreases. The above results imply that rapid anealing not only renovates lattice strains and disfigurements but also accelerates the forming of Fe-Ni solid solution.