Nanoindentation and Nano‐Compresion Testing of Ni ₃ Al Precipitates

Abstract

Using an AFM-based instrumented nanoindentation system, the nanoindentation response of γ' particles (Ni 3 Al) in a Ni-base single crystal superalloy CMSX-4 was characterized to demonstrate the influence of the softer γ matrix on the measurement of nano-mechanical properties of γ' particles. The properties of the γ' particles were measured after both a standard and a coarsening heat treatment, in which the initially sub-micron sized cuboidal γ' particles transformed to large, irregularly shaped γ' precipitates with dimensions in excess of 30 μm. The measured nano-hardness of the coarsened γ' precipitates in CMSX-4 appears to increase slightly with the increasing load. Nano-compression testing of cuboidal γ' particles, electrolytically extracted from a CMSX-4 after a standard solution and age heat treatment, was also performed. With a maximum value of 10 GPa, the measured yield stress of these dislocation-free γ' particles approaches the ideal strength and is equivalent to ~G/17. Compared to the measured yield strengths of γ' phase in its bulk crystal form, these nano-compression results are more than a factor of 33 higher. Additionally, the 'softening' effect of Ga + ion implantation on the strength of dislocation-free nanocrystals was also assessed. The resulting yield strengths of cuboidal γ' precipitates imaged with a focused ion beam were at least 5 GPa lower than those that had not been subjected to Ga + ion implantation.

Grain size and misorientation evolution in linear friction welding of additively manufactured IN718 to forged superalloy AD730™

“…Figure 9 also shows that AD730 TM displays a strain hardening behavior while IN718 alloy (as-SLM or H-SLM) strain softening. These findings are in agreement with those reported by other authors on dissimilar solid-state welding of IN718 to an alloy with higher strength [7,17,18]. It must also be noted that in all welded joints, the strengthening phases were found to be completely dissolved in the WZ.…”

“…In recent years, LFW has also been applied to the assembly of components made of Nickel (Ni)-based superalloys, as well as in many other engineering applications, ranging from automotive to agriculture, and allowing for new designs and applications [1,2]. In addition to overcoming the disadvantages associated with mechanical assembly techniques, such as fretting fatigue and thermomechanical fatigue [3][4][5] observed in conventional blade-disk setups, or cracking and distortions in fusion-based welding assemblies, LFW joints are characterized by higher mechanical properties and extended component life in service [6,7].…”