Effect of solidification conditions on selection and formation characteristics of intermetallics in light alloys

EPSRC research grant K34818

Summary of the final report

A solidification microstructure selection map has been determined for Al-3.5wt%Fe - 0 to 8.5%wt%Si for growth velocity V over the range 0.01 to 2mm/s and temperature gradient ~15K/mm, equivalent to solidification cooling rates 0.15 to 30K/s, comparable with commercial direct chill or permanent mould casting conditions. Primary intermetallic changes from thetaAl₁₃Fe₄ to alpha_cAlFeSi and then beta-AlFeSi with increasing silicon alloying content Co. The transition Co values decrease with increasing V as predicted by competitive growth modelling. Matrix microstructure changes for Eu1 (Al-Al₁₃Fe₄ eutectic) or Eu2 (Al-Al₆Fe) to Eu3 (Alalpha_cAlFeSi) and Eu4 (Al-Si), also featuring fine alpha-Al dendrites, with increase in C_o and V. Primary Al_l3Fe₄ forming at 0 < Co < 4wt%Si showed increased silicon content with increasing V and Co, together with significant morphological changes measured and predicted earlier. Two new methods of preparing sound feedstock samples for Bridgman solidification have been developed.

Contact:

Prof H Jones,
Department of Engineering Materials,
University of Sheffield,
Mappin Street, Sheffield S1 3JD
Telephone: 0114 222 5508
Fax: 0114 222 5943