FATIGUE PROPERTIES OF AL-MG ALLOYS WITH AND WITHOUT SCANDIUM

The fatigue properties, e.g. HCF strength, crack growth of small surfa ce and long-through cracks, of two wrought Al-5Mg-0.3Mn-0.06Zr alloys without and with scandium (0.25%) were investigated in vacuum, air and salt water. The alloy with scandium showed a higher tensile yield str ess, higher fatigue strength values and a higher resistance against mi crocrack growth, due to the presence of coherent Al-3 (Sc, Zr) precipi tates and a very fine subgrain structure. The scandium free alloy exhi bited a slightly higher resistance against macrocrack growth, due to t he coarser grain structure. (C) 1997 Elsevier Science S.A.