THERMAL STABILITY OF RAPIDLY SOLIDIFIED Al-Fe-X ALLOYS

Aluminum alloys prepared by rapid solidification are prospective materials for many special applications. In this work, microstructure of three rapidly solidified aluminum alloys has been studied and compared. Alloys of following chemical composition were studied: Al-11Fe, Al-7Fe-4Ni and Al-7Fe-4Cr (wt. %). Nickel and chromium were chosen as alloying elements due to the low solubility and diffusivity in aluminum matrix which improve mechanical properties and thermal stability at elevated temperatures. Samples in the form of thin ribbons were prepared by melt spinning technique. Microstructure of investigated alloys was studied by scanning electron microscopy (SEM). Phase composition was determined by X-ray diffraction (XRD). Vickers hardness (HV 0.005) was measured to estimate mechanical properties as well as thermal stability after long term annealing (500 h) at 300 and 400 degrees C. Rapidly solidified alloys consist predominantly of supersaturated solid solution of alloying elements in aluminum on the wheel side and fine particles of intermetallic phases on the free side. Material hardness decreases with increasing temperature. Chromium improves the thermal stability more than nickel.