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Inconel 706 (IN706) alloy is commonly used in aircraft engines and power plant components that must meet very high performance requirements. The stabilization treatment has a significant effect on the precipitation and evolution of the reinforcing phases of the alloy, favoring the creep properties and adversely affecting the room-temperature tensile properties. However, the mechanism of the effect of the stabilization treatment on the mechanical properties of the alloys remains unclear. In this study, the effect of stabilization treatment time on the microstructure and tensile properties of IN706 alloy was investigated. The results showed that as the stabilization time gradually increased, the tensile strength remained basically unchanged (about 1250 MPa), the yield strength decreased from 1031 MPa to 985 MPa, and the plasticity decreased from 28.2% to 20.2%. The stabilization treatment induces the precipitation of granular, rod-shaped, and needle-like η phases at grain boundaries, accompanied by the appearance of a precipitate free zone (PFZ). Since the η phase is enriched with Ti and Nb, its precipitation along the grain boundary results in the depletion of Ti and Nb in the surrounding regions, thereby constraining the precipitation of the γ′ and γ″ phases, resulting in the appearance of PFZ. With increasing stabilization time, the size increase and volume fraction decrease in γ′-γ″ co-precipitates due to the precipitation of η-phase precipitates, leading to a decrease in their yield strength. Combined with in situ tensile tests, it was found that the decrease in the elongation of the stabilization treatment samples was due to the presence of η phase at the grain boundaries, which induced stress concentration and cracking at the grain boundaries. The results show that the mechanical properties of the material were gradually enhanced as the stabilization time decreased. This means it can help to choose the suitable process for IN706 alloy in different service conditions. [ABSTRACT FROM AUTHOR]

In this study, 2195 Al–Cu–Li alloys with a remarkable layered structure were fabricated through spray deposition, hot extrusion, and three distinct heat treatment processes (namely, solid solution treatment (ST), artificial peak-aging (PA), and artificial over-aging (OA)). The samples subjected to varying heat treatments are revealed to exhibit an exceptional combination of strength and ductility at 77 K, in contrast to their counterparts at 298 K. Specially, the mechanical properties of the PA samples are enhanced to various degrees with decreasing temperature from 298 K to 77 K. It is found that the synergistic effects of dense dislocations and uniform T 1 precipitates, as well as their extensive interactions, are responsible for the exceptional strain hardening capacity at cryogenic temperature. Particularly, multiple slip systems and the temperature-dependent relative slip distance are beneficial for the formation of dense dislocations and thus for enhancing ductility at 77 K. Furthermore, the observation of rare and small microcracks, along with intergranular delamination at 77 K, suggests that layered structures impede the plastic instability of the alloy and improve its ductility. These findings provide valuable insights into the deformation behaviors of high-strength aluminum alloys for cryogenic applications. • The spray deposited 2195 Al–Cu–Li alloy displays a superior strength-ductility synergy at cryogenic temperature. • Superior cryogenic strength-ductility synergy of the PA sample stems from the synergy of multiple strengthening mechanisms. • The temperature-dependent relative slip distance enhances ductility at 77 K. • Observations of rare and small cracks and intergranular delamination at 77 K improve its ductility. [ABSTRACT FROM AUTHOR]

This study conducts a comprehensive examination of the microstructural and dislocation dynamics of AlSi10Mg alloys under various thermal conditions, utilizing quasi in-situ Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM) analyses. The research focuses on comparing the microstructural response of as-built and T6 heat-treated samples to mechanical stress at both ambient (298 K) and cryogenic (77 K) temperatures. EBSD analysis underscores the grain stability under applied strain, while TEM investigations expose notable variations in dislocation mobility influenced by temperature, with a particular emphasis on the interaction between dislocations and silicon particles at cryogenic temperatures. An observed increase in Geometrically Necessary Dislocation (GND) density at 77 K points to enhanced resistance to plastic deformation, suggesting mechanisms of cryogenic strengthening. The findings illuminate the impact of heat treatment in augmenting the mechanical properties of the alloy, shedding light on its potential applications in aerospace and cryogenic environments. • Enhanced mechanical properties in SLM AlSi10Mg alloys at cryogenic temperatures, showing significant differences in strength and ductility. • Cryogenic conditions led to an increase in yield and tensile strengths for both as-built and heat-treated samples, with notable distinctions in ductility. • Quasi-in situ EBSD and TEM analyses revealed higher dislocation density and the activation of multiple slip systems at 77 K. • T6 heat treatment improved ductility and showed the interaction between dislocations and Si particles in TEM. [ABSTRACT FROM AUTHOR]

Heat treatment is the most common method to relieve residual stress and to adjust tensile properties in additively manufactured material. However, the well-known strengthening factors (e.g., dislocation density, cellular sub-structure, low angle grain boundaries, nano-oxide particle) in selective laser melted 316 L (SLM 316 L) are strongly influenced by heat-treatment temperature. In this work, horizontal and vertical oriented SLM 316 L specimens are heat treated from 550 °C to 1150 °C, followed by tensile tests and microstructural characterization. With increasing temperature, strength (e.g., yield strength, ultimate tensile strength) is found to decrease and elongation is found to increase. The heat treatments of 550 °C, 650 °C and 750 °C lead to coarsening of cellular sub-structure. Furthermore, the cellular sub-structure and melt boundaries annihilate at 950 °C. When the temperature reaches 1150 °C, SLM 316 L has finished recrystallization with volume fraction of nano-oxide particles increasing greatly. Based on microstructural characterization, the proposed relationship, considering strengthening mechanisms of cellular sub-structure, nano-oxide particle and grain boundaries, give satisfactory accuracy to predict yield strength for horizontal orientation. The yield strength for vertical orientation can also be predicted by this relationship when modified by consideration of anisotropy of columnar grains and lack-of-fusion defects. The anisotropy and lack-of-fusion lead to 5.4% reduction in yield strength for the vertical orientation. This work establishes quantitative relationships for heat treatment-microstructure-property, in which the anisotropy of tensile properties is considered. • In SLM 316 L, the microstructural evolution and tensile properties after heat treatment of larger temperature range (from 550 °C to 1150 °C) are investigated quantitatively. • The yield strength relationship based on microstructural characterization is established and has satisfying predicting accuracy. • Considering anisotropicof columnar grains and lack-of-fusion defects, the model also provides accurate prediction of vertical orientation. • This research establishes the relationship of process-structure-property in SLM 316 L. [ABSTRACT FROM AUTHOR]