Kan Song

Fabrication and Characterization of Al 2 O 3 /Y 3 Al 5 O 12 Eutectic in situ Composite Ceramics by Double Side Laser Zone Remelting Method: Fabrication and Characterization of Al 2 O 3 /Y 3 Al 5 O 12 Eutectic in situ Composite Ceramics by Double Side Laser Zone Remelting Method

采用激光区熔凝固技术制备大尺寸Al 2 O 3 /Y 3 Al 5 O 12 (YAG)共晶自生复合陶瓷, 考察双面区熔条件下大尺寸氧化物共晶陶瓷的熔化及凝固成形规律, 采用扫描电镜、能谱和X射线衍射对其凝固组织特征进行了表征和分析. 研究结果表明:在优化的凝固工艺下, 激光双面区熔增加了熔凝层的厚度, 获得了熔凝层厚度8.2 mm, 长度65.0 mm, 致密度达98.5%±1%的Al 2 O 3 /YAG共晶陶瓷; 共晶熔凝层厚度随激光扫描速率的减小而增加, 随激光功率的增大而增大, 并且致密度随着激光功率的增大呈现先增大后减小的趋势; 双面区熔后的Al 2 O 3 /YAG共晶陶瓷微观组织由均一分布、相互交织的Al 2 O 3 和YAG共晶相组成, 共晶层片间距较小(1.0~3.5 μm), 且与凝固速度满足Jackson-Hunt公式; 共晶间距随扫描速率的增大逐渐减小; 双面区熔界面处共晶组织生长具有连续性, 界面结合良好; 共晶陶瓷的Vickers硬度为(18.6±1.0) GPa.采用激光区熔凝固技术制备大尺寸Al 2 O 3 /Y 3 Al 5 O 12 (YAG)共晶自生复合陶瓷, 考察双面区熔条件下大尺寸氧化物共晶陶瓷的熔化及凝固成形规律, 采用扫描电镜、能谱和X射线衍射对其凝固组织特征进行了表征和分析. 研究结果表明:在优化的凝固工艺下, 激光双面区熔增加了熔凝层的厚度, 获得了熔凝层厚度8.2 mm, 长度65.0 mm, 致密度达98.5%±1%的Al 2 O 3 /YAG共晶陶瓷; 共晶熔凝层厚度随激光扫描速率的减小而增加, 随激光功率的增大而增大, 并且致密度随着激光功率的增大呈现先增大后减小的趋势; 双面区熔后的Al 2 O 3 /YAG共晶陶瓷微观组织由均一分布、相互交织的Al 2 O 3 和YAG共晶相组成, 共晶层片间距较小(1.0~3.5 μm), 且与凝固速度满足Jackson-Hunt公式; 共晶间距随扫描速率的增大逐渐减小; 双面区熔界面处共晶组织生长具有连续性, 界面结合良好; 共晶陶瓷的Vickers硬度为(18.6±1.0) GPa.

Directional Solidification and Characterization of Al2O3/Er3Al5O12 Eutectic In Situ Composite by Laser Zone Remelting

Directionally solidified (DS) oxide eutectic in situ composites are attracting increasing attention because of their unique properties and potential applications to high temperature structural materials, optical or electronic devices. Among the alumina-based eutectic composites, DS Al2O3/Er3Al5O12(EAG) eutectic is considered to be promising candidate for use as selective emitter at high temperature. In this work, eutectic in situ composites of Al2O3/EAG rods having smooth surface and full density are successfully prepared by directional solidification using the laser zone remelting method, aiming to investigate the growth characteristic of this novel binary eutectic under high temperature gradient. The microstructure is investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). The Al2O3/EAG eutectic presents a very fine irregular network structure consisting of only -Al2O3 and Er3Al5O12 phases without grain boundaries and amorphous phases between interfaces. The eutectic interphase spacing is strongly dependent on the laser scanning rate, rapidly decreasing at the sub-micron levels for the samples grown at high rate. Furthermore, the microstructural formation and evolution of the composite are analyzed and discussed.