The Influence of High‐Temperature Deformation and Heat Treatment on Microstructure of AF1410 Ultra‐High Strength Steel

Abstract

Hot compression tests of AF1410 ultra‐high strength steel are studied on a Gleeble‐3800 thermo‐mechanical simulator. The dynamic recrystallization behavior and microstructure evolution are analyzed with compression tests at deformation temperatures of 850–1150 °C and strain rates of 0.001–1 s−1. The results suggest that dynamic recrystallization grains of AF1410 steel grow with deformation temperature rising and strain rate decreasing. The coarse dynamic recrystallization grains are obtained at high temperature with low strain rate. The fine grains are obtained at low temperature with high strain rate, while recrystallization is incomplete in this situation. Fine equiaxed grains are obtained at deformation temperatures of 950–1050 °C and strain rates of 0.1–1 s−1, when dynamic recrystallization occurs completely. Then, the hot compression specimens are normalized at 900 °C for 1 h and tempered at 680 °C for 6 h. Compared with the compression specimens, it is found that there are relatively uniform fine grains after the heat treatment, and the grain size ranged from 14 to 23 µm. TEM analysis results show that coarse precipitates mainly include needle‐shaped M2C carbide and square‐shaped M23C6 carbide. There is no coherent relationship between the carbides and the martensite matrix.