GB630211A - Improvements in or relating to the heat treatment of magnesium base alloys - Google Patents

Abstract

In a method of inhibiting grain growth in magnesium base alloy castings, the casting is treated in a series of short interrupted thermal treatments each treatment consisting of heating at a temperature for a time sufficient to cause only a portion of the desired solid solution to form and no one of which is in itself capable of placing the entire desired amount of solid solution forming elements in solid solution but all of which seriatim achieve the desired effect and cooling is effected between successive thermal treatments under conditions which cause precipitation of some of said solid solution forming elements. The heating may be to a temperature within 40 DEG F. of that of incipient fusion. An alloy consisting of 9 per cent Al, 2 per cent Zn, 0.2 per cent Mn and the balance Mg and unavoidable impurities may be heated for four hours at 775 DEG F., cooled to 400 DEG F., reheated for four hours at 775 DEG F. cooled to 400 DEG F., re heated for five hours at 775 DEG F. and cooled to room temperature. The alloys may contain 2-12 per cent Al, 0.50-08 per cent Mn, 0.5 per cent Si, 0.1-0.3 per cent Ca, 0.02 per cent iron, 0.0001 to 0.05 per cent Be and Zn, Sn, Cd, Pb or Ag between 0.1 and 10 per cent.