Microstructural evolution of directionally solidified DZ125 superalloy castings with different solidification methods  

作　　者：Ge Bingming Liu Lin Zhang Jun Li Yafeng Fu Hengzhi Liu Xiaofu 

机构地区：[1]State Key Laboratory of Solidification Processing,Northwestern Polytechnical University [2]Shenyang Research Institute of Foundry

出　　处：《China Foundry》2013年第1期24-28,共5页中国铸造（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.50827102 and 50931004);National Basic Research Program of China(Grant No.2010CB631202 and No.2006CB605202);High Technology Research and Development Program of China(Grant No.2007AA03Z552)

摘　　要：The properties of Ni-base superalloy castings microstructure, and different solidification methods have are closely related to the uniformity of their as-cast serious effect on microstructural uniformity. In this paper, the influences of high rate solidification （HRS） process （with or without superheating） and liquid metal cooling （LMC） process on the microstructure of DZ125 superalloy were investigated. Blade-shape castings were solidified at rates of 40 pm.s-1 to 110 tJm.s1 using HRS process and a comparative experiment was carried out at a rate of 70 IJm.s1 by LMC process. The optical microscope （OM）, scanning electron microscope （SEM） were used to observe the microstructure and the grain size was analyzed using electron back scattered diffraction （EBSD） technique. Results show that for the castings by either HRS or LMC process, the primary dendrite arm spacing and size of 7＇ precipitates decrease with increasing the withdrawal rate; the dendrites and 7＇ precipitates at the upper section of the blade are coarser than those in the middle, especially for the HRS castings without high superheating technique. When the withdrawal rate is 70 iJm.s1, the castings by HRS with high superheating technique have the smallest PDAS with fine 7＇ precipitates; while the size distribution of 7＇ precipitates is more homogenous in LMC castings, and the number of larger grains in LMC castings is smaller than that in the HRS castings. Moreover, high superheating technique yields smaller grains in the castings. Both the LMC method and HRS with high superheating technique can be used to prepare castings with reduced maximum grain size.The properties of Ni-base superalloy castings are closely related to the uniformity of their as-cast microstructure,and different solidification methods have serious effect on microstructural uniformity.In this paper,the influences of high rate solidification(HRS) process(with or without superheating) and liquid metal cooling(LMC) process on the microstructure of DZ125 superalloy were investigated.Blade-shape castings were solidified at rates of 40 μm·s-1 to 110 μm·s-1 using HRS process and a comparative experiment was carried out at a rate of 70 μm·s-1 by LMC process.The optical microscope(OM),scanning electron microscope(SEM) were used to observe the microstructure and the grain size was analyzed using electron back scattered diffraction(EBSD) technique.Results show that for the castings by either HRS or LMC process,the primary dendrite arm spacing and size of γ' precipitates decrease with increasing the withdrawal rate;the dendrites and γ' precipitates at the upper section of the blade are coarser than those in the middle,especially for the HRS castings without high superheating technique.When the withdrawal rate is 70 μm·s-1,the castings by HRS with high superheating technique have the smallest PDAS with fine γ' precipitates;while the size distribution of γ' precipitates is more homogenous in LMC castings,and the number of larger grains in LMC castings is smaller than that in the HRS castings.Moreover,high superheating technique yields smaller grains in the castings.Both the LMC method and HRS with high superheating technique can be used to prepare castings with reduced maximum grain size.

关 键 词：directional solidification microstructural evolution high rate solidification liquid metal cooling Ni-base superalloy 

分 类 号：TG146.15[一般工业技术—材料科学与工程]