微晶玻璃焊料在连接过程中的晶化行为研究

Crystallization Behavior of Glass Ceramic Filler During Joining Process

采用一种添加Li2O和Fe2O3的CaO-Al2O3-SiO2基微晶玻璃连接氧化铝陶瓷。通过采用热分析（DTA）、扫描电镜（SEM）和X射线衍射分析（XRD）等方法,研究了微晶玻璃焊料在连接过程中的晶化行为及其对接头力学性能的影响。结果表明,在传统的晶化处理过程中,此玻璃中能够析出锂辉石（LiAlSi2O6）、硅灰石（CaSiO3）、钙铁镏石（Ca3Fe2Si3O（12））和钙长石（CaAl2Si2O8）四种晶体。然而,当采用此玻璃连接氧化铝陶瓷时,微晶玻璃的晶化过程与连接工艺密切相关。由于缺少足够的形核驱动力,采用焊后直接冷却的连接工艺只能获得完全玻璃态的接头中间层。通过在降温过程中引入形核–晶化的热处理工艺,促进了玻璃中间层的晶化,并且能够通过改变晶化温度来调整中间层的相组成。另外,晶化相的种类对接头力学性能有重要影响。当中间层中只形成钙长石时,接头强度达到247.5MPa;而当中间层中有锂辉石或钙铁镏石析出时,接头强度仅为10～135MPa。

A CaO-Al2O3-SiO2 system glass ceramic with addition of Li2O and Fe2O3 was developed to join alumina ceramics. The crystallization behavior of the glass interlayer during joining process was investigated by DTA, SEM and XRD. The effect of joint microstructure and phase composition on the joint strength was study. The results show that LiAlSi2O6, CaSiO3, Ca3Fe2Si3O12, and CaAl2Si2O8 are formed in the glass during conventional crystallization treatment. However, when the glass was used to join alumina, the crystallization behavior of the glass interlayer is closely related to the heating cycle. Direct cooling from joining temperature leads to completely amorphous interlayer formation, due to the absence of enough nucleation driving force. An extra nucleation-crystallization treatment during cooling contributes to crystallization of the glass interlayer in joints. Meannhile, the phase composition of glass inter- layer can be adjusted by changing the crystallization temperature according to the DTA results. In addition, the joint strength is highly sensitive to crystalline phases in the interlayer. When there is only CaAl2Si2O8 formed in the interlayer, the joint strength reaches as high as 247.5 MPa. By contrast, when there is LiAlSi2O6 or Ca3Fe2Si3O12 formed in the interlayer, the joint strength is only 10-135 MPa.