Abstract
Experiments have been made on the heat-treatment and the stress-corrosion tests of 25 different alloys in the Al corner of the Al-Zn-Mg Alloy system, containing up to 30%Zn and 10%Mg. The most suitable temperature of the solution treatment for practical purposes is 440° and the most practically useful compositions are 4-10%Zn and less than 2%Mg, provided the total contents of Zn and Mg do not exceed 10%. These alloys have the highest tensile strength when aged at 150°, after quenching from 440° into hot or cold water. They cannot obtain superior mechanical properties than super-duralumin, when aged at room temperature. Alloys of the Al-Mg-Zn2 line have the highest saturated hardness as shown in the former report by the authors ; and alloys containing mere Zn or alloys on the Al-T(Al2Mg3Zn3) line have considerable hardening effects.The Al-MgZn5 section diagram was investigated by thermal analysis and microscopic examinations peritecto-eutectic reaction at 323° was discovered to form MgZn5.
