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采用真空等温热变形试验机在恒应变速率和真空环境条件下,对挤压态镍基粉末高温合金试样20 mm×20mm×50 mm进行了等温应变梯度变形试验研究。分别在最大应变速率0.001、0.01、0.1、1 s-1和变形温度1070℃条件下,所有试样最大应变处等温变形至真应变1.0。结果表明:随应变速率的升高,异常晶粒长大位置由大应变区逐渐移至小应变区,异常晶粒长大变得严重,而在高应变速率时,温升越大,试样异常晶粒长大的情况越严重;借助EBSD技术可以计算晶粒形变程度,大应变区域具有较大的晶粒形变程度,异常晶粒长大区域具有较小的晶粒形变程度,由于晶粒形变程度高的区域位错密度大,晶内储存能量较高,易于发生再结晶,晶粒形变程度低的区域位错密度小,位错优先用于晶粒长大。
The isothermal strain gradient deformation test of 20 mm × 20 mm × 50 mm specimens of extruded nickel base powder superalloy was carried out with vacuum isothermal deformation tester at constant strain rate and vacuum environment. Under the conditions of the maximum strain rate of 0.001, 0.01, 0.1, 1 s-1 and the deformation temperature of 1070 ℃, the maximum strain of all samples was isothermal deformation to true strain of 1.0. The results show that as the strain rate increases, the location of abnormal grain growth gradually shifts from the large strain zone to the small strain zone, and the abnormal grain growth becomes serious. At high strain rate, The more serious the abnormal grain grows; the degree of grain deformation can be calculated by EBSD technique, the large strain area has larger degree of grain deformation, and the abnormal grain growth area has smaller degree of grain deformation. Since the grain Dislocation density is high in regions with high degree of deformation, high energy is stored in the crystal, recrystallization is easy to occur, dislocation density in regions with low degree of grain deformation is small, and dislocation is preferred for grain growth.