Ag-Sn-La合金粉末的氧化组织研究

Oxidation Microstructure of Ag-Sn-La Alloy Powder

摘要:

采用X 射线衍射仪、金相显微镜和扫描电镜，研究了Ag-Sn-La合金粉末的氧化组织。结果表明：Ag-Sn-La系合金粉末氧化后主要由Ag、SnO2和La2Sn2O7 3种相组成；合金元素含量不同，Ag-Sn-La合金粉末具有不同的氧化动力学特征、氧化组织和氧化机制。Ag-5.2Sn-3.4La合金粉末的起始氧化温度为350 ℃，氧化速度较快，元素La和Sn发生原位氧化，但柱状晶上La的快速优先氧化使得合金内部出现条状的氧化物；Ag-6.87Sn-1.28La合金粉末从加热一开始便发生缓慢氧化，在300 ℃以后开始快速氧化，元素La和Sn发生原位氧化，原位生成的氧化物颗粒弥散分布在银基体上；Ag-9.26Sn-0.44La合金粉末的起始氧化温度为567 ℃且氧化速度较慢，元素La发生原位氧化，而部分Sn在浓度梯度的驱动下向外扩散，生成的氧化锡颗粒主要分布在粉末边界，而La的氧化物则弥散分布在银基体上。

Abstract:

The microstructure of Ag-Sn-La alloy powder after oxidation was investigated by XRD, OM and SEM. The results show that Ag, SnO2 and La2Sn2O7 phases are formed in Ag-Sn-La alloy powder after oxidation. Ag-Sn-La alloy powder has different oxidation kinetic characters, oxidation microstructures and oxidation mechanisms due to the different contents of alloying agent. The starting oxidation temperature of Ag-5.2Sn-3.4La alloy powder is 350 oC and the oxidation velocity is fast. Both element Sn and La are oxidized in situ and strip oxides are formed due to the fast oxidation of element La during the oxidation of Ag-5.2Sn-3.4La alloy powder. The oxidation velocity of Ag-6.87Sn-1.28La alloy powder is slow when the temperature is from room temperature to 300 oC and that is fast when the temperature is above 300 oC. Both element Sn and La are oxidized in situ and the formed oxides are uniformly distributed in the silver matrix. The starting oxidation temperature of Ag-9.26Sn-0.44La alloy powder is 567 oC and the oxidation velocity is slow. Element La is oxidized in situ and element Sn diffuses from the inner to the surface due to the driving of concentration gradient. La oxides are uniformly distributed in the silver matrix and Sn oxides are mainly distributed on the grain boundary after Ag-9.26Sn-0.44La alloy powder oxidation.