浇铸制度对K4750合金室温拉伸性能的影响  

Effect of Pouring System on Microstructure and Properties of K4750 Alloy

作　　者：赵鹏飞 王旻 欧美琼 马颖澈[1] 刘奎[1] Zhao Pengfei;Wang Min;Ou Meiqiong;Ma Yingche;Liu Kui(Shi-changxu Innovation Center for Advanced Materials,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China)

机构地区：[1]中国科学院金属研究所师昌绪先进材料创新中心,辽宁沈阳110016 [2]中国科学技术大学材料科学与工程学院,辽宁沈阳110016

出　　处：《稀有金属材料与工程》2023年第11期3809-3817,共9页Rare Metal Materials and Engineering

基　　金：中国博士后科学基金(2020M671403)。

摘　　要：K4750合金是一种新型铸造镍基高温合金,在700~750℃具有较为优异的力学性能,有望代替K4169合金使用。但是K4750合金的室温拉伸塑性波动性较大,合金室温拉伸性能、凝固组织和浇铸制度之间的关系尚不明确。本工作采用不同的浇铸温度和型壳冷却条件制备了多组K4750合金试棒,采用单轴拉伸测试了合金的室温拉伸性能,评价了合金室温拉伸性能对浇铸温度和型壳冷却速率变化的敏感性,并通过组织表征进行了机理阐述。结果表明,浇铸温度降低,合金晶粒尺寸显著减小,合金屈服强度小幅提高,塑性保持稳定;而当型壳冷却速率降低后,合金室温拉伸断后延伸率显著下降。这主要是由于型壳冷却条件显著影响了MC碳化物的析出特征。当冷却速率较低时,晶界析出粗大的长条状MC碳化物,其在应力作用下易于产生内部裂纹,加速合金晶界失效降低合金塑性。为优化K4750合金的室温拉伸性能,应重点关注型壳或铸件在浇铸后的冷却速率与晶界MC碳化物析出形态,抑制粗大晶界碳化物产生,提高晶界塑韧性。K4750 alloy is a new cast nickel-based superalloy with excellent mechanical properties at 700-750℃and is expected to replace K4169 alloy.However,the tensile plasticity of K4750 alloy at room temperature fluctuates,and the relationship among room temperature tensile properties,solidification microstructure,and casting parameters is still unclear for this alloy.In this work,several K4750 alloy test bars were prepared with various casting temperatures and shell cooling conditions,and tested at room temperature by uniaxial tension.Sensitivity of the alloy’s room temperature tensile properties to changes in casting temperature and shell cooling rate was evaluated,and the mechanism was elucidated by microstructure characterization.Results show that the grain size of alloy drops significantly with decreasing casting temperature,and the yield strength of the alloy slightly increases while the plasticity remains stable.When the cooling rate of the shell decreases,the fracture elongation of the alloy decreases significantly at room temperature.This is mainly because the cooling condition of mold shell significantly affects the precipitation characteristics of MC carbides.When the cooling rate is low,MC carbides tend to precipitate at grain boundaries in coarse and strip-like shapes.MC carbides are prone to internal cracks under stress,accelerating the intergranular failure of material and reducing the plasticity of alloy.In order to optimize the tensile properties of K4750 alloy at room temperature,more attention should be paid to the cooling rate of mold shell after casting and the precipitation morphology of intergranular carbides,prohibiting the formation of coarse intergranular carbides to improve the grain boundary plasticity of the alloy.

关 键 词：K4750合金 浇铸制度 力学性能 碳化物 晶界 

分 类 号：TG244[金属学及工艺—铸造] TG146.15[一般工业技术—材料科学与工程]