Microstructure and phase composition in high-strength aluminium alloys produced by a splat-cooling technique

Abstract

Rapid solidification (RS) experiments have been carried out on high-strength AIZnMgCuX alloys (X = Zr, Ti, Cr or Mn) using the rotating-wing splat-cooling technique. The resulting particles ("splats") were examined by light-microscopy, X-ray diffraction (Guinier-technique) and TEM. In comparison to industrially produced powders the microstructure was refined by about a factor of two. The alloying elements could be kept partially in solution and/or led to metastable phases which precipitated during solidification or handling before subsequent examination. Heat treatment of the rapidly solidified splats generated a relatively homogeneous and dense precipitation of several metastable and/or stable phases. In some cases the RS technique used could not prevent special high-melting phases from precipitating already in the melt. These phases acted as quite effective grain size stabilizers during subsequent heat treatment. The higher solidification rates are concluded to show potential for improving the mechanical properties of these alloys.