Doctoral Dissertations

Abstract

"A lightweight castable alloy was sought to reduce the MIL-PRF-32269 class II cast steel perforated armor's weight with the requirement that the material had to be manufactured utilizing existing foundry technology and without incurring large alloy cost increases to meet property requirements. Literature on wrought age hardenable Fe-Mn-Al-C alloys suggested this alloy system could achieve weight reduction through high aluminum concentrations with the highest reported strengths exceeding 2 GPa for a Fe-30Mn-9Al-0.9C composition. Even though ballistic testing had not been conducted on this system, high strain rate data of wrought alloys showed excellent work hardenability; greater than existing ballistic metals. Cast material property information was severely limited, thus, a systematic approach was employed to develop casting and processing techniques and assess related structure property relationships of a nominal silicon modified Fe-30Mn-9Al-0.9C-0.5Mo alloy for ballistic use. Castability was addressed first as this information was crucial for making test coupons and assisting foundries with production of MIL-PRF-32269 ballistic test plates. Four silicon concentrations were investigated for fluidity, microstructure, liquidus, solidus and dendrite coherency point. Silicon was added because it is known to increase fluidity of other ferrous alloys and has also been shown to eliminate a brittle ß-Mn phase in wrought Fe-Mn-Al-C alloys. Of the four silicon modified fluidity compositions, two were selected for heat treat property evaluation on the basis of microstructure. Hardness, strength, and ductility were measured (hardness is the only MIL-PRF-32269 measured property). The alloy with the highest ductility was selected for high strain rate evaluation. The strain rate testing results were the final means to lock in the alloy composition and heat treatment for solid plate ballistic testing. While conducting V₅₀ ballistic testing, phosphorus content was correlated to ballistic impact energy. Further testing was conducted to examine phosphorus, quench sensitivity, and aging Charpy V-Notch effects. The culmination of this thesis work resulted with positive ballistic threat testing revealing the alloy investigated here meets the Army's MIL-PRF-32269 ballistic requirements and reduces P900 weight by 13%"--Abstract, page iv.

Advisor(s)

Van Aken, David C.
Chin, Ernest S. C.

Committee Member(s)

Hilmas, Greg
Peaslee, Kent D., 1956-2013
Medvedeva, Julia E.
Richards, Von

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Metallurgical Engineering

Sponsor(s)

United States. Army Research Office

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2009

Journal article titles appearing in thesis/dissertation

  • Literature review of age hardening Fe-Mn-Al-C alloys
  • Effect of silicon content on the fluidity and microstructure of Fe-Mn-Al-C alloys
  • Tensile, high strain rate compression and microstructural evaluation of lightweight age hardenable cast Fe-30Mn-9Al-XSi-0.9C-0.5Mo steel
  • Advancements in steel for weight reduction of P900 armor plate
  • Phosphorus and thermal processing effects on Charpy V-notch impact toughness of lightweight Fe-30Mn-9Al-XSi-0.9C-0.5Mo alloy steel
  • Quench sensitivity of cast Fe-30Mn-9Al-XSi-0.9C-0.5Mo lightweight steel

Pagination

xxiii, 226 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2009 Ryan Andrew Howell, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Armor -- Technological innovationsAustenitic stainless steel -- MetallurgyStrains and stresses

Thesis Number

T 9527

Print OCLC #

503563271

Electronic OCLC #

750531686

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