Different effects of γ′ and η phases on the physical and mechanical properties of superalloys

Effect of Nano-Sized γ′ Phase on the Ultrasonic and Mechanical Properties of Ni-Based Superalloy

“…The γ′ precipitates throughout the heat treatment process altered the elastic modulus but showed little impact on the density of the alloy. According to a previous study [ 15 , 32 ], the Young’s modulus of the γ′ phase (210 GPa) was approximately 11% higher than the γ matrix (190 GPa). As a result, the Young’s modulus of the superalloy increased with the volume faction of the γ′ phase in the microstructure, which increased the ultrasonic longitudinal velocity of the superalloy.…”

“…Ultrasonic properties, which result from the interactions between the ultrasonic wave and the microstructures of materials, have been extensively used for optimizing heat treatment processes [ 12 , 13 ] and characterizing the microstructures [ 14 , 15 ] and mechanical properties [ 16 , 17 ] of materials. Ultrasonic velocity and attenuation reflect variations in the grain size [ 18 , 19 ], volume fraction, the size of the precipitated phase [ 20 , 21 , 22 , 23 ], the type of precipitated phase [ 15 , 24 ], and the defects during the heat treatment of superalloys. Ultrasonic velocity has been reported to increase with the formation of the precipitate phases, whereas the dissolving or coarsening of precipitates leads to decreases in velocity [ 12 , 14 , 15 , 16 , 20 , 21 , 22 , 25 ].…”

“…Ultrasonic velocity and attenuation reflect variations in the grain size [ 18 , 19 ], volume fraction, the size of the precipitated phase [ 20 , 21 , 22 , 23 ], the type of precipitated phase [ 15 , 24 ], and the defects during the heat treatment of superalloys. Ultrasonic velocity has been reported to increase with the formation of the precipitate phases, whereas the dissolving or coarsening of precipitates leads to decreases in velocity [ 12 , 14 , 15 , 16 , 20 , 21 , 22 , 25 ]. This is mainly because the formation and dissolution of the intermetallic precipitates change the composition of an alloy, improving the elastic modulus and increasing the ultrasonic velocity [ 14 , 16 , 20 , 22 ].…”

“…This is mainly because the formation and dissolution of the intermetallic precipitates change the composition of an alloy, improving the elastic modulus and increasing the ultrasonic velocity [ 14 , 16 , 20 , 22 ]. The ultrasonic velocity of an alloy increases with the increase in the volume fraction of the nano-sized γ′ phase and η phase, but carbide has little effect on ultrasonic velocity [ 14 , 15 , 24 ]. Further, it has been found that the change in ultrasonic velocity caused by the change in the microstructure of a superalloy is consistent with the change in mechanical properties.…”

Abnormal grain growth under solution-aging treatments enables convergence mechanical properties of a Fe-Ni-Cr based austenitic alloy

“…However, as illustrated in figures 11(a), (b), cellular η phase could still be observed at some GBs. According to the [34], η phase tends to dissolve into the matrix at elevated temperatures, but the exact dissolution behavior may be related to local thermodynamic conditions at GBs. It is expected that the η phase can also impede the movement of the interface [35].…”