Masters Theses

Mingli Yu

Date of Award

8-1991

Degree Type

Thesis

Degree Name

Master of Science

Major

Metallurgical Engineering

Major Professor

Charlie R. Brooks

Committee Members

W. T. Becker, E. S. Clark

Abstract

Five practices of anealing and cold rolling have been conducted in a 3104 A1 alloy to investigate their influences on earing and the mechanical properties. Among these influences, slow heat-up rate (15°C/hr) to the annealing temperature of 332°C, which simulated batch annealing, and rapid heat-up rate (about 140°C/min.), which simulated strip annealing, both annealings proceeding 2 hours of time, were investigated, and some of the practices involved an intermediate cold rolling of 35% (CR35). The as-received (AR) condition was "hot" rolled state, and all final condition in the five practices was cold rolled 88% (CR88), so called H19 state. The tensile mechanical properties after the five practices were found out being independent of the direction of testing in the final CR88 state. The yield and tensile strengths were slightly lower for practices involving the intermediate CR35, however, these practices had markedly higher 45° earing. The higher heat-up rate gave a finer annealed grain size, but the heat-up rate had no effect (other steps of the processing being the same) on earing behavior. Scanning electron microscopy and optical microscopy were used to examine the primary particle size, distribution, and density in the annealed state in all the five practices. However, no clear correlation with the earing occurrence. X-ray diffraction, ultrasonic technique and pole figure were used to examine the texture in the five practices. The AR condition gave a complex texture (copper type) similar to that of all the final CR88 conditions. Results from both ultrasonic and pole figure techniques were consistent with those from the earing tests, practices involving the intermediate CR35 having higher earing and correspondently higher texture intensities. X-ray diffraction results were to reflect the major texture component variations during the different procedures m each of the five practices. It appears that the finer microstructural features produced after the CR35 and intermediate annealing are responsible for the high earing observed. Therefore, further and deeper investigation should be focussed on this in other techniques such as transmission electron microscopy, etc.

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