Abstract: Several binary and ternary magnesium-thorium alloys were investigated using additions of manganese, cerium, aluminum, zinc, calcium, and zirconium. The properties of magnesium-thorium alloys anmd also the effects of the additions on the properties at both room and elevated temperature were examined. The alloys were cast in a 20-mm diameter metallic mould heated to 50-60 deg C. The main method of investigating the properties consisted of short-time (30 sec) and long-time (60 min) hardness measurements. The hardnesses were measured at room temperature and 300 deg C using a 10-nmm ball and a 100-kg load. The alloys were stabilized at 300 deg C for 100 hours before testing. Measurements were also made after quenching from 565 deg C. A marked increase occurred in the hardness of magnesium in the cast and stabilized conditions with increase in thorium content to 4%. Further increases in thorium content to 6 - 10% had littie effect. The hardness decreased somewhat after the stabilization treatment. After quenching from 565 deg C, the hardness increased with increasing thorium content up to 10%. The prolonged hardness gave extremely high values. From microstructural and thermal analysis it was shown that the magnesiumthorium system is of the eutectic type. The eutecticmore » consists of alpha -solid solution and the compound Mg/sub 5/Th, melting at 40-42% thorium and 580 deg C. The solubility of thorium at the eutectic temperature is 5% and at 300 deg C, 0.5%. Microhardness measurements showed that the hardness of the compound was 306 kg/mm/ sup 2/, the eutectic was 118 kg/mm/sup 2/, and the solid solution was 74 kg/mm/ sup 2/, corresponding to a hardness for magnesium of 47 kg/mm/sup 2/. The effect of the additions of the various elements was studied using an alloy containing 3% thorium. Cerium had the greatest effect on the properties at room temperature, the hardness continuously increasing up to 6% cerium. Calcium and zinc had a positive effect up to 0.5-1%, further additions showing no change. Low additions of manganese and aluminum gave a decrease in hardness. Funther additions gave an increase. The greatest effect on the prolonged hardness at 300 deg C was shown by 0.6-1% manganese. Cerium also showed an increase, but to a lesser degree. (OTS)« less
Publication Year: 1960
Publication Date: 1960-01-01
Language: en
Type: article
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