Masters Theses

Sachin Mehta

Abstract

"A systematic study of the effect of heat treatment variables on the properties can be carried out successfully using a design of experiment method combined with the Jominy End Quench technique. It's a useful work to develop an optimized heat treatment for cast aluminum alloys. The Jominy End Quench has been successfully used to determine the effect of quench rate on the final heat treated properties of wrought alloys and, in practice, it is equally applicable to cast alloys. Meanwhile, the desired effects of heat treatment parameters on the properties are difficult to carry out due to the large number of variables, and the fact that experimental noise in the treatment and testing procedure confounds the results. In order to sort out the effect of the coarse microstructure, a hardness measurement procedure was developed.

This first issue is addressed through performing sequential hardness tests along the length of a cast bar of both A356 and B319. Different hardness scales and techniques are evaluated, with precision and accuracy being the figure of merit. From these tests an appropriate hardness technique was developed. With respect to the macro-segregation, heat transfer and mechanical properties are affected. The mechanical properties will be accounted for in the test matrix by looking at the different solidification rates. The heat transfer issue required that the instrumented JEQ samples be quenched and the cooling rates measured for both B319 and A356. Cooling from the end of the bar gives a continuous range of quench rates, which can be used to compare to cooling rates in any given part of the bar. The sample can then be heat-treated at a given set of conditions. Cooling curve calculations were done for the alloys and the nature of the curve determined.

The results of these tests were compared to the calculated heat transfer models, which use known thermal conductivity values for the two alloys. The best technique for using the JEQ with the cast aluminum alloys is developed from the tests; and the techniques developed can also be used in the development of future aluminum alloys. A few other heat treating modifications were evaluated that may provide for better process control and mechanical properties"--Abstract, page iii.

Advisor(s)

Newkirk, Joseph William

Committee Member(s)

Mishra, Rajiv S.
Johnson, James W., 1930-2002

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Metallurgical Engineering

Publisher

University of Missouri--Rolla

Publication Date

Spring 2001

Pagination

x, 57 pages

Note about bibliography

Includes bibliographical references (pages 54-56).

Rights

© 2001 Sachin Mehta, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Thesis Number

T 7895

Print OCLC #

47235876

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