GB644776A - An aluminium base alloy - Google Patents

Abstract

An aluminium base alloy has the following composition: Zn 3.50-9.99 per cent, Mg 0.75-2.50 per cent, Mn 0.39-1.80 per cent, Sn and/or Cr 0.11-1.50 per cent, Nb 0.01-0.50 per cent, Si 0.01-2.00 per cent, Fe 0.01-1.75 per cent, Al the remainder. The composition of the alloys is subject to the following qualifications. Sn will be present exceeding 0.01 per cent and preferably exceeding 0.05 per cent when the Zn content is 7.0 per cent and over or when the Si content is 0.2 per cent and below, but in the absence of Sn the Mg available after the formation of Mg2Si with all the Si present will always be less than 35 per cent of the Zn present and will exceed 1.50 per cent when the Zn content is 8.0 per cent and over. When the Mg content is 2.0 per cent and over Sn will be present in the range 0.01-0.10 per cent, and when the Mg content is 2.0 per cent and below either the Fe content or the Si content or both are below 0.4 per cent, up to 2.5 per cent of Cu may be present, so that when the Cu content exceeds 1.1 per cent and the Mg content exceeds 2.0 per cent, Sn may be present up to 1.25 per cent. Ni may be present up to 1.49 per cent, so that the sum of the Ni and Mn contents is less than 2.0 per cent when the Zn content is 6.5 per cent and below. The alloy may contain up to 1.5 per cent of Co. Grain refining elements Ti and/or B may be present which together with the Nb do not exceed a total of 0.75 per cent. One or more of the elements Sb, Ca, Ce, Ag, Be, Tl, Mo, Bi, As, W, V, Ga, Th, Li, Ta, Cd, La, Te, Yt, Zr and Pb may be present up to a total of 1.5 per cent and individually not exceeding 1.25 per cent. One or more of the elements Na, K, Ba, C, Sr, P may be present not exceeding 0.25 per cent in total. The alloy, in the form of a sand casting, die casting or worked part may be solution heat-treated within the range 460-550 DEG C and then quenched in water or other medium. An ageing treatment may then be given at 100-170 DEG C.