Term of Award

Spring 2022

Degree Name

Master of Science, Mechanical 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 Mechanical Engineering

Committee Chair

Mingzhi Xu

Committee Member 1

Jingjing Qing

Committee Member 2

Drew Snelling

Abstract

According to the Hall-Petch equation, the refinement of grains in metals increases the yield strength of the material. Austenite grain size influences the fineness of microstructural constituents in the ferrous alloys. It is well studied that cerium and titanium refine the austenite in steels and some gray irons, but no studies have been done to systematically explore the effects of cerium and titanium additions on austenite in ductile iron. This study sought to determine the effects of selected levels of these elements on the grain size within ductile iron. A hypoeutectic iron was chosen for testing as the proeutectic phase is austenite and effects of alloy additions on austenite can be studied directly. Cerium additions in the amounts of 0.01 wt.% and 0.03 wt.% and titanium additions in the amounts of 0.02 wt.% and 0.04 wt.% were tested. The effectiveness of each of these elements as heterogeneous nuclei formers was determined using three methods: direct secondary dendrite arm spacing measurement, liquidus undercooling and recalescence study, and tensile testing. The results of the study showed that cerium refined the austenite effectively and the refinement improved as the amount of cerium increased, although the elongation of the ductile iron was not decreased For titanium, the dendrite arms showed significant refinement in faster cooling conditions but showed coarsening in slower cooling conditions. The elongation was also slightly reduced with no appreciable gain in strength. There are also signs that these additions negatively impacted the graphite phase although the assessment of this mechanism is outside the scope of this study.

Research Data and Supplementary Material

No

Share

COinS