CAJ | 학술논문

利用变形温度为1120～1210℃、应变速率为0.1～20 s-1以及变形量为15%～60%的等温热压缩实验研究了GH4700合金的热变形行为.通过对低温和高应变速率条件下的形变热效应进行修正，得到准确的流变曲线，推导出描述峰值应力与温度和应变速率等变形参数的本构方程，并得到 GH4700合金热变形表观激活能为322 kJ.组织分析表明，动态再结晶是热变形过程中最主要的软化方式，再结晶形核方式为应变诱发晶界迁移，变形温度升高和应变速率增大均有利于再结晶形核.再结晶发展阶段，随着变形量的增大和变形温度的升高，动态再结晶比例增加，在应变速率-温度坐标中，再结晶比例等值线呈反“C”形式.采用分段函数描述了不同应变速率下 GH4700合金动态再结晶晶粒尺寸与变形参数的关系.
이용변형온도위1120～1210℃、응변속솔위0.1～20 s-1이급변형량위15%～60%적등온열압축실험연구료GH4700합금적열변형행위.통과대저온화고응변속솔조건하적형변열효응진행수정，득도준학적류변곡선，추도출묘술봉치응력여온도화응변속솔등변형삼수적본구방정，병득도 GH4700합금열변형표관격활능위322 kJ.조직분석표명，동태재결정시열변형과정중최주요적연화방식，재결정형핵방식위응변유발정계천이，변형온도승고화응변속솔증대균유리우재결정형핵.재결정발전계단，수착변형량적증대화변형온도적승고，동태재결정비례증가，재응변속솔-온도좌표중，재결정비례등치선정반“C”형식.채용분단함수묘술료불동응변속솔하 GH4700합금동태재결정정립척촌여변형삼수적관계.
The hot deformation behavior of nickel-based superalloy GH4700 was investigated by isothermal com-pression tests at temperatures of 1120 to 1210℃and strain rates of 0.1 to 20 s-1 with deformations of 15%to 60%. The flow curves at high strain rate and low temperature were corrected in consideration of the deformation-heating effect. Accurate constitutive equations were established between peak stress and deformation parameters, i.e., temperature and strain rate. The activation energy of the alloy was determined to be 322 kJ. Microstructure analysis results show that dynamic recrystallization (DRX) is the principal softening mechanism during hot working. Strain-induced-grain-boundary-migration is the nucleation mechanism, which is promoted by the increase of both temperature and strain rate. The ratio of DRX grains is increased by temperature and strain, while the iso-ratio contour of DRX exhibits an “anti-C” type in the strain rate-temperature coordinate system. The relationship between DRX grain size and deformation parameters was calculated to be a piecewise function which depends on strain rate.