Microstructure Characterization and Small Punch Test Analysis in Nickel-Based Alloy 617 by High Energy Neon Implantation

Abstract

Nickel-based alloys are good candidate structural materials for ultra-high temperature gas-cooled reactors due to their excellent mechanical properties under high-temperature conditions. The operating environment in the compact high-temperature gas-cooled reactor proposes more stringent requirements with higher displacement and temperatures higher than 700 °C. The irradiation resistance of nickel-based alloy 617 is evaluated by 120 MeV neon ion irradiation. The neon ion fluence is set with reference to the number of helium atoms generated by the reaction of (n, α) in nickel-based alloy under actual service conditions. With the application of an energy gradient degrader, the irradiation damage area is more uniform with increasing depth. The neon ion irradiation causes no significant surface damage to alloy 617 while the evolution of defects such as inherent dislocation lines is affected, thus leading to the deterioration of mechanical properties. By using the small punch test to analyze the irradiation effects, it is found that the neon ion irradiation results in the tendency of irradiation softening and does not lead to changes in the basic fracture characteristics under different annealing conditions. After annealing at 700 and 800 °C for 2 h, the irradiation embrittlement trend is intensified, with the fracture characteristic values of irradiated samples showing a more obvious decreasing trend.

An Improved Correlation for the Estimation of the Yield Strength from Small Punch Testing

“…A summary of all simulation results is listed in Table 3. Both methods for the evaluation are included (𝐹 based on bi-linear fitting [6] vs. 𝐹 based on Equations ( 4), (5), and ( 8)-( 11)).…”

“…For the purpose of this investigation, larger displacements were not needed. Consequently, the constitutive equations do not include ductile damage, as this develops only at higher displacements [5]. In the postprocessing, two types of SP curves were generated: the force-displacement curve F(v) (reaction force at the pilot node of the punch versus punch displacement) and the force-deflection curve F(u) (reaction force at the pilot node of the punch versus the central bottom deflection of the plate).…”

“…It provides estimations of mechanical properties with small amounts of material and has received much attention as a high-throughput characterization method. For example, this is of major interest for irradiated and activated materials [4,5]. The primary output of the quasi-static SP test is the punch force as a function of the punch displacement-force-displacement curve F(v)-or as function of specimen deflection-force-deflection curve F(u).…”

Martensite Decomposition and Ultrafine Grain Formation during Small Punch Creep Testing of Additively Manufactured Ti64

“…The method was first developed on an imposed displacement rate mode in order to characterize the yield of the material, mainly on nuclear industry steels [8]. The method then evolved for testing different materials such as Al [9], Mg [10], Ni [11], or Fe-Al [12]-based alloys or composites. It was also used on load control mode to test the creep behaviour of the material; this latter technique is known as small punch creep testing (SPCT).…”