Hot deformation behaviors of a 9Cr oxide dispersion-strengthened steel and its microstructure characterization

The hot deformation behaviors of a 9 Cr oxide dispersion-strengthened(9 Cr-ODS) steel fabricated by mechanical alloying and hot isostatic pressing(HIP) were investigated. Hot compression deformation experiments were conducted on a Gleeble 3500 simulator in a temperature range of 950–1100°C and strain rate range of 0.001–1 s^(-1). The constitutive equation that can accurately describe the relationship between the rheological stress and the strain rate of the 9 Cr-ODS steel was established, and the deformation activation energy was calculated as 780.817 kJ/mol according to the data obtained. The processing maps of 9 Cr-ODS in the strain range of 0.1–0.6 were also developed. The results show that the region with high power dissipation efficiency corresponds to a completely recrystallized structure. The optimal processing conditions were determined as a temperature range of 1000–1050°C with strain rate between 0.003 and 0.01 s^(-1).

Effect of heat treatment processing on microstructure and tensile properties of Ti-6Al-4V-10Nb alloy

Effects of heat treatment processing on the microstructure and mechanical properties of Ti-6Al-4V-10Nb alloy were investigated. The microstructures were investigated by SEM, TEM and XRD, and the mechanical properties were evaluated by tensile tests at room and elevated temperatures. The results indicate that the lath-like and globular primary α phase, secondary α phase and β phase are obtained after forging and heat treatment processing. The size of secondary α phase is much smaller than that of primary α phase. After heat treatment, the volume fraction of primary α phase is decreased, and that of secondary α phase is increased. With the increase of solution temperature, the volume fraction of primary α phase is gradually decreased, and that of secondary α phase is obviously increased. The yield strength and tensile strength of Ti-6Al-4V-10Nb alloy are significantly enhanced with the solution temperature increasing.

Thermal analysis and tests of W/Cu brazing for primary collimator scraper in CSNS/RCS

To the transverse beam collimation system in a rapid cycling synchrotron,an important component is the primary collimator,which improves emittance of the beam halo particles such that the particles outside the predefined trajectory can be absorbed by the secondary collimators.Given the material properties and power deposition distribution,the beam scraper of the primary collimator is a0.17 mm tungsten foil on a double face-wedged copper block of 121.5 mm x 20 mm.The heat is transferred to the outside by a φ34 mm copper rod.In this paper,for minimizing brazing thermal stress,we report our theoretical analysis and tests on brazing the tungsten and copper materials which differ greatly in size.We show that the thermal stress effect can be controlled effectively by creating stress relief grooves on the copper block and inserting a tungsten transition layer into the copper block.This innovation contributes to the successful R&D of the primary collimator.And this study may be of help for working out a brazing plan of similar structures.