Reduced partitioning of plastic strain for strong and yet ductile precipitate-strengthened alloys

Abstract

When a material that contains precipitates is deformed, the precipitates and the matrix may strain plastically by different amounts causing stresses to build up at the precipitate-matrix interfaces. If premature failure is to be avoided, it is therefore essential to reduce the difference in the plastic strain between the two phases. Here, we conduct nanoscale digital image correlation to measure a new variable that quantifies this plastic strain difference and show how its value can be used to estimate the associated interfacial stresses, which are found to be approximately three times greater in an Fe-Ni2AlTi steel than in the more ductile Ni-based superalloy CMSX-4®. It is then demonstrated that decreasing these stresses significantly improves the ability of the Fe-Ni2AlTi microstructure to deform under tensile loads without loss in strength.

Strain partitioning between matrix and precipitates during fatigue deformation of 2.25Cr–Mo steel

“…Owing to less number of active slip systems in BCC-iron matrix leads to greater strain hardening during high deformation. The strain hardening of the BCC-matrix leads to load/strain portioning to second phase during high strain rate deformation [6]. The presence of different precipitates leads to different deformation behaviour depending on the extent of strain hardening of BCC-matrix.…”

Small-Scale Mechanical Testing

“…This observation suggests that the increased ductility of one steel over the other is related to the greater work-hardening ability of the ferrite. DIC on micropillars was used (107) to quantify the plastic strain difference between matrix and precipitate which is accommodated by GNDs. The large strain mismatch in an Fe-Ni 2 AlTi steel accounts for its low ductility, in comparison to the lower mismatch between γ and γ in a more ductile nickel-based superalloy.…”

High-resolution digital image correlation study of the strain localization during loading of a shot-peened RR1000 nickel-based superalloy

“…However, this resolution is not high enough to quantify the strain associated to different microstructural features, which are usually less than few microns in size. Recently, the development of surface patterning methods such as self-assembling of nanoparticles on the surface [18], electron beam lithography [19,20], deposition of Pt using FIB [21] and gold remodelling [22][23][24][25][26][27][28][29] have improved the achievable spatial resolution and high-resolution digital image correlation (HRDIC) can be used to measure strain at the submicron scale. Among this collection of patterning methods, the remodelling of a thin gold layer previously deposited on the sample surface is a versatile and simple method that provides one of the highest resolutions for extensive areas available to date [25,[29][30][31].…”