采用DSC对Sr、Ca复合添加后的AZ31镁合金在熔化和凝固过程中的吸氧增重情况进行了观察,发现当温度高于100℃时AZ31合金就开始增重,550℃镁合金的氧化速率明显增加,在熔融状态下氧化增重比率高达1.75%,而当添加Sr、Ca含量分别为0.3%和0.6%(质量分数)时,670℃氧化速率才明显增加,熔融状态下其氧化增重比率降至0.35%,说明Sr、Ca复合添加显著降低了AZ31镁合金在高温下的氧化速率.讨论认为Sr、Ca复合添加降低AZ31镁合金的吸氧增重比率:一方面是因为Sr、Ca与O2结合生成致密的氧化膜,阻碍了镁合金的进一步吸氧增重;另一方面,Sr、Ca的复合添加提高了Mg17 Al12相的稳定性,降低了合金相与氧的反应速率.
In this paper,the oxidation weight gains of the AZ31 with different contents of Sr and Ca have been analyzed by the differential scanning calorimeters (DSC)during the melting and solidification process.The re-sults show that the AZ31 weights are increasing when the temperature get to 100 ℃ and the oxidation rates are remarkably increasing at 550 ℃.The oxidation weight ratios are as high as 1.75% in the molten situation.How-ever,when the contents of Sr and Ca change to 0.3wt% and 0.6wt% the oxidation rate is remarkably increasing at 670 ℃,and the oxidation weight ratio is only 0.35%.It concludes that the added Sr and Ca are beneficial to reduce to the oxidation rate of the AZ31 .The reasons are that the density of the oxide film produced by the reac-tion among Sr,Ca and O2 prevent the oxidation weight gain continuously increasing.On the other side,the in-creasing stability of Mg17 Al12 phase is beneficial to reduce the oxidation rate when the Sr and Ca compound add-ed.
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