激光双面区熔Al_2O_3/Y_3Al_5O_(12)共晶自生复合陶瓷的制备与表征

Fabrication and Characterization of Al_2O_3/Y_3Al_5O_(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Al2O3/Y3Al5O12（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Al2O3/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Al2O3/YAG共晶陶瓷微观组织由均一分布、相互交织的Al2O3和YAG共晶相组成,共晶层片间距较小（1.0~3.5μm）,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.

Al2O3/YAG eutectic in situ composite ceramics were prepared by double side laser zone remelting（DSLZR） with aiming at investigating the melting and solidification rules of oxide eutectic ceramics with large size under DSLZR condition.The solidification microstructures were characterized by SEM,XRD and EDS.The results show that solidified layer thickness of eutectic ceramics is enhanced by DSLZR.The eutectic ceramic plates with density up to 98.5%±1% are obtained,in which the thickness is 8.2 mm,and the length is 65.0 mm.The thickness of solidified layer is increased with decreasing laser scanning rate and increasing laser power.The density is initially increased and then decreased with the increase of laser scanning rate.The eutectic ceramic obtained by DSLZR is only consisted of uniform and interweaved Al2O3 and YAG phases.The relation between the eutectic spacing（λ;only 1.0~3.5 μm） and solidification rate（v） agrees with the Jackson-Hunt formula.With the increase of laser scanning rate,the eutectic spacing reduces.Furthermore,the growth of eutectic at double side remelting interface is continuous,so the binded interface is very well.The eutectic ceramic obtained has high Vickers hardness（（18.6±1.0） GPa） due to the fine solidification microstructure.