College of Graduate Studies: Theses & Dissertations

Term of Award

Spring 2026

Degree Name

Master of Science, Manufacturing Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Manufacturing Engineering

Committee Chair

Jingjing Qing

Committee Member 1

Mingzhi Xu

Committee Member 2

Haijun Gong

Abstract

Gray iron is composed primarily of an iron matrix and flake graphite, with the higher percentage of volume taken up by the iron matrix. The iron matrix is the transformation product of austenite, and this prior austenite structure is understood to affect the final grain structure. Grain structure affects the properties of a metal, with a finer structure recognized as beneficial for most properties. Thus, the refinement of austenite structure has potential in improving the material properties of gray iron. This study aims to advance the limited knowledge about the control of austenite grain size via elemental additions. Building off extant work, various elemental (Al, Ba, Ca, Ce, Mg, Mn, Sr, Ti, or Zr) additions were investigated against a pure silicon addition as a baseline. The use of a Direct Austempering After Solidification (DAAS) heat treatment permitted austenite grain boundaries to be retained for macrographic analysis, and austenite grain morphology was correlated to tensile and fatigue properties of a gray iron. While most elements showed an ability to refine the austenite grain structure over the silicon baseline, the effect on material properties was less conclusive with level of elemental additions used. Grain refinement did result in an improvement of tensile strength in several alloy addition conditions. Grain refinement led to improved fatigue life. Calcium and titanium treated iron showed improvements of grain refinement, ultimate tensile strength, as well as fatigue limit.

Research Data and Supplementary Material

No

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Metallurgy Commons

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