AVS 61st International Symposium & Exhibition
    Thin Film Tuesday Sessions
       Session TF+AS+EM-TuA

Paper TF+AS+EM-TuA11
High-Throughput Assessment of the Composition Dependence of Initial Passivating-Al2O3-Scale Establishment in AlxFeyNi1-x-y Alloy Thin Films

Tuesday, November 11, 2014, 5:40 pm, Room 305

Session: Thin Film: Growth and Characterization II
Presenter: Matthew Payne, Carnegie Mellon University, DOE - National Energy Technology Laboratory
Authors: M. Payne, Carnegie Mellon University, DOE - National Energy Technology Laboratory
J. Miller, Carnegie Mellon University, DOE - National Energy Technology Laboratory
A.J. Gellman, Carnegie Mellon University, DOE - National Energy Technology Laboratory
Correspondent: Click to Email
AlFeNi-containing alloys capable of forming passivating Al2O3 scales are designed for high-temperature structural applications requiring robust oxidation resistance. Mechanical considerations typically dictate that Al content be minimized, but a critical concentration, NAl*, is minimally required to promote the initial establishment of a continuous Al2O3 layer. Current understanding of how NAl* evolves across multi-component composition spaces is limited, being based largely on experiments that are constrained by the need for meticulous preparation and characterization of large numbers of single-composition samples. The study of properties across alloy composition space can be greatly accelerated using composition spread alloy films (CSAFs), materials libraries comprised of continuous lateral composition gradients. Properly designed CSAFs can contain every possible composition of a ternary alloy. In this work, ~120 nm-thick AlxFeyNi1-x-y CSAFs spanning the entire ternary range (x = 0 → 1, y = 0 → [1-x]) over an area of ~1 cm2 were prepared. A variety of spatially resolved techniques were developed for effective, high-throughput characterization of early oxidation behaviors in the CSAFs. Energy-dispersive X-ray spectroscopy was used to measure changes in CSAF oxygen content as a function of both alloy composition and oxidation time. Raman spectroscopy allowed specific oxide phases formed in different regions of the composition space to be identified. X-ray photoemission depth profiling was performed at select locations of interest to determine composition and chemical state in CSAF cross-sections. These methods were used to study oxidation across AlxFeyNi1-x-y composition space in both dry and moist air at 700 K, and have enabled the identification of continuous boundaries separating regions of phenomenologically unique oxidation behaviors, including the NAl*(x,y) boundary for each environment. The results enhance fundamental understanding of early-stage AlxFeyNi1-x-y oxidation and can contribute to the accelerated design of next-generation alloys.