Concentration-Dependent Tungsten Effects on Short-Range Order and Deformation Behavior in Ni-W alloys

TL;DR

This study systematically investigates how varying tungsten content in Ni-W alloys influences short-range order, deformation mechanisms, and strengthening, revealing that higher W levels induce SRO that enhances mechanical properties.

Contribution

It provides a comprehensive analysis linking W concentration to SRO development and mechanical behavior, using advanced experimental and computational techniques.

Findings

Strong SRO emerges above 30 wt% W

SRO promotes planar slip and twin formation

High grain boundary strengthening coefficient in Ni-38W

Abstract

Ni-W based medium heavy alloys offer a promising pathway to bridge the density-strength gap between tungsten heavy alloys and ultrahigh-strength steels. In this study, the effects of W concentration on short-range order (SRO), deformation behavior, and grain boundary chemistry of Ni-xW alloys in the range x = 0 to 38 wt% were systematically investigated using a suite of advanced characterization and modeling techniques, including synchrotron X-ray diffraction, transmission electron microscopy, atom probe tomography, and first-principles thermodynamic simulations. Our study reveals that strong SRO emerges when W content exceeds about 30 wt%, producing distinct diffuse scattering and significantly enhancing strain-hardening capacity. During deformation, the presence of SRO promotes planar slip and twin formation, leading to strong dislocation interactions and elevated flow stress. Hall-Petch analysis demonstrates an exceptionally high grain boundary strengthening coefficient (ky about 1100 MPa micrometer^(1/2)) in Ni-38W, underscoring the intrinsic strengthening effect associated with SRO. First-principles cluster expansion coupled with Monte Carlo simulations reveals that increasing W content enhances SRO tendency through the stabilization of Ni4W-type local configurations. These findings establish a mechanistic link between W concentration, SRO evolution, and mechanical response, providing new insights for designing high-density, high-strength Ni-W based alloys with optimized performance.