Showing 3 results for Precipitate
M. S. Kaiser, A. S. W. Kurny,
Volume 8, Issue 4 (12-2011)
Abstract
Microstructure and properties of the Al-6Si-0.3Mg alloys containing scandium (0.2 to 0.6wt %) were investigated. The microstructure was observed by optical microscopy, the hardness was determined by Vickers tester and phase transformation was investigated by differential scanning calorimetry (DSC) technique. The results showed that scandium can refine dendrites, enhance hardness in the aged alloys and suppress softening effect during prolonged ageing treatment.
M. S. Kaiser,
Volume 11, Issue 4 (12-2014)
Abstract
The evaluation of texture as a function of recrystallization has been characterized for directly cold rolled Al-6Mg, Al-6Mg-0.4Sc and Al-6Mg-0.4Sc-0.2Zr alloys. Samples were annealed isothermally at 400 °C for 1 to 240 minutes to allow recrystallization. Recrystallization kinetics of the alloys is analyzed from the micro-hardness variation. Isothermally annealed samples of aluminum alloys were also studied using JMAK type analysis to see if there exists any correlation between the methods. Recrystallization fraction behavior between two methods the scandium added alloys show the higher variation due to precipitation hardening and higher recrystallization behavior. The scandium and zirconium as a combined shows the more variation due to formation of Al3(Sc, Zr) precipitate. From the microstructure it is also observed that the base Al-Mg alloy attained almost fully re-crystallized state after annealing at 400 °C for 60 minutes
Seyed Hossein Razavi, Mehdi Safavi, M. Reza Aboutalebi, Seyed Mehdi Abbasi,
Volume 21, Issue 0 (3-2024)
Abstract
This study examines how solution treatment temperature affects the dissolution of fine-grained areas (FGAs) that form during hot rolling of René 65 nickel-based superalloy. These FGAs, which are rich in sub-micron to micron-sized primary γ' precipitates (γ'I) and located mainly in shear bands, remained stable after sub-solvus treatments below 1055 °C. They dissolved gradually with increasing temperature and disappeared completely above 1115 °C. The resulting microstructural changes, along with high-temperature tensile properties and creep behavior in the 1055–1115 °C range (followed by aging at 760 °C for 8 h), were evaluated. Raising the solution temperature reduced the FGA volume fraction and improved tensile elongation, while yield strength (YS) and ultimate tensile strength (UTS) remained largely unchanged. At 1095 °C, creep life at 730 °C / 530 MPa exceeded 100 h without fracture and exhibited a notably lower steady-state creep rate. These improvements appear linked to the elimination of secondary γ' depleted zones around the former FGAs, which produced a more uniform secondary γ' distribution, greater crack path deflection, and continued Zener pinning by remaining primary precipitates. However, solution treatment at 1115 °C caused grain growth and coarsening of secondary precipitates, which reduced creep performance. Overall, 1095 °C provided the best compromise for microstructural uniformity and balanced high-temperature properties in hot-rolled René 65.
