On the origin of a remarkable increase in the strength and stability of an Al rich Al-Ni eutectic alloy by Zr addition

Abstract

The effect of Zr addition to Al rich binary a-Al-Al 3 Ni eutectic cast alloy (Al-3.1 at.% Ni) in enhancing the microstructural stability and strength at high temperature is demonstrated. On subsequent heat treatment after casting, nanometric coherent L1 2 ordered Al 3 Zr precipitates form inside the a-Al that strengthen the alloy. Additionally, remarkable stability of eutectic microstructure was observed even after 100 h of annealing at 400 C. The synergetic effect of the strengthening of the a-Al matrix by coherent Al 3 Zr precipitates and the low coarsening rate of the Al 3 Ni rods results in a significant increase in high temperature hardness and yield strength of the alloy. The tensile yield strength of the annealed Al-3.1Ni-0.15Zr alloy (400 C, 10 h) tested at 250 C is found to be 185 ± 10 MPa, which is 1.5 times higher than the corresponding binary Al-3.1Ni alloy. The experimentally determined average rod size (radius) during annealing at 400 C follows the classical matrix diffusion controlled LSW-based coarsening model for both binary Al-3.1Ni and ternary Al-3.1Ni-0.15Zr alloys. The calculated coarsening rate constant values based on modified LSW coarsening model are 10.3 and 4.1 nm 3 /s for Al-3.1Ni and Al-3.1Ni-0.15Zr alloys, respectively. Atom probe tomographic (APT) investigations of the heat-treated ternary alloy unambiguously reveal segregation of Zr solute at the aAl/Al 3 Ni interface in addition to the presence of the strengthening Al 3 Zr ordered precipitates in the a-Al matrix. The segregation hinders the interdiffusion of Al and Ni in the eutectic and, thereby, increasing the stability of the eutectic phase at high temperature.

Plastic and low-cost axial zero thermal expansion alloy by a natural dual-phase composite

“…12 )—there exist widespread lattice strains caused by shear bands. That is, the lamellar morphology from the eutectic reaction enhances the alloys’ mechanical performance via dual-phase synergetic interaction 20 , 23 , 31 , 36 – 39 .…”

“…In this work, we conducted a one-step strategy to design plastic and low-cost ZTE alloy by a hypo-eutectic or hyper-eutectic reaction in a binary system 23 – 25 . Iron is one of the most earth-abundant elements; its conventional phase, α-Fe, has high plasticity and normal positive thermal expansion (PTE).…”

Plastic and low-cost zero thermal expansion alloy by a natural dual-phase composite

“…S7)-there exist widespread lattice strains caused by shear bands. That is, the lamellar morphology from eutectic reaction enhances the alloys' mechanical performance via dual-phase synergetic interaction 20,23,31,[36][37][38][39] .…”

“…In this work, we employ a one-step strategy to design plastic and low-cost ZTE alloy by a hypo-or hypereutectic reaction in a binary system [23][24][25] . As we know, iron is one of the most earth-abundant elements; its conventional phase, α-Fe, has high plasticity and normal positive thermal expansion (PTE).…”

Precipitation kinetics in metallic alloys: Experiments and modeling

“…Reducing the interfacial energy can help the nucleation process [151] and when slow diffusing species are present at the precipitate interfaces, strain fields are reduced and/or the interfacial energy is reduced, the coarsening resistance can be enhanced [152]. Many systems exhibit solute segregation at the precipitate-matrix interfaces with resulting combinations of these effects, such as in Al-Cu [153][154][155][156][157][158], Al-Cu-Li [19,159], Al-Cu-Ag [160,161], Al-Zn-Mg [162,163], Al-Mg-Si-Cu [164], Al-Ni-Zr [165], Mg alloys [166,167], precipitates in steels [168,169], or superalloys [170][171][172][173].…”