Students: Sarah Gnall
Project: Optimization of Niobium and Silicon Concentrations in Monel Alloys For Mechanical Property Enhancement | View Poster (PDF)
Major: Materials Science and Engineering
Advisor: John DuPont
Abstract
Monel alloys, utilized across over 25 different industries, boast excellent corrosion resistance and toughness.1 However, their phase transformations and microstructure from heat treatment remain poorly understood.2 Niobium and Silicon are thought to improve mechanical properties since they promote a material-strengthening precipitate.1 Therefore, investigating eight Monel alloys with varying niobium and silicon concentrations (2.90wt% to 4.42wt% Si, 0.50wt% to 2.7wt% Nb) aims to enhance mechanical properties through precipitation hardening by acquiring knowledge of the material’s phase transformations.
Initial focus on microhardness hypothesized that silicon-rich precipitates with minimal niobium boosts microhardness.3 To determine if this was supported or not, samples underwent the following heat treatment schedule: solution annealing at 950°C for 24 hours, water quenching, aging at 600°C at varying aging times (0, 1, 3, 7, and 14 hours), then water quenched again. Samples were then microhardness tested according to ASTM E384, which revealed alloys with less than 1.50wt% Nb peak in microhardness after 7 hours of aging. Alloys with less than 1.50wt% Nb and have 3.0wt% Si exhibit improved microhardness compared to its as-cast condition. Future analysis using Scanning Electron Microscopy, X-ray Diffraction for phase analysis, and Light Optical Microscopy will provide concrete conclusions to ultimately achieve improved mechanical properties.
References:
[1] C. Farnin, The Influence of Nominal Composition on the Solidification Behavior, Tensile Properties, and Weldability of Cast Monel Alloys. ResearchGate (2023).
[2] A. G. Evgenov, G. I. Morozova, V. I. Lukin, Special features of phase transformations in an alloy of the Ni-Cu-Si-Fe-Mn system - metal science and heat treatment. SpringerLink (2006).
[3] P. Mukhopadhyay, G. K. Dey, Precipitation in the nicu-base alloy Monel K-500. Materials Science and Engineering (2003).
About Sarah Gnall
Sarah Gnall is a senior at Lehigh University, majoring in Materials Science and Engineering (MSE) and minoring in Social and Personality Psychology. As a Clare Boothe Luce (CBL) Research Scholar for the P.C. Rossin College of Engineering and Applied Science, she has been conducting undergraduate research under Professor John N. DuPont in the MSE department with funding from both the CBL program and Steel Founders’ Society of America. Sarah’s research interests revolve around welding, mechanical behavior of materials, and corrosion. Following graduation, she will be joining ExxonMobil full-time as a Materials Engineer in Houston, Texas, where she will combine her research and energy interests to help ExxonMobil with the energy transition. Beyond research, Sarah’s interests include Formula 1 racing, music, traveling, and community service.