Type of Document	Thesis
Author	Heffner, William Ryan
URN	etd-08222008-095621
Title	Microstructure Development in 6000 series Aluminum Alloys Processed via Equal Channel Angular Extrusion
Degree	Master of Science
Department	Mechanical Engineering, Department of
Advisory Committee	Advisor Name Title Peter N. Kalu Committee Chair Daudi Waryoba Committee Member Carl Moore Outside Committee Member
Keywords	Grain Superplastic Deformation Plastic Severe Size
Date of Defense	2008-08-15
Availability	unrestricted
Abstract Industry standard 6061 and 6063 Aluminum alloys were processed by equal channel angular extrusion (ECAE) at room temperature using a Bc route with a constant feed rate of 0.25 mm/s through a die angle of 90° between the die channels. The influence of ECAE processing on the evolution of the microstructure, microtexture and microhardness in the material was studied using orientation imaging microscopy (OIM), X-ray diffractometry, and Vickers microhardness testing. Detailed analysis was carried out on samples of the as-received, one, two, four and eight pass conditions. The microhardness data showed that the hardness of the Al-6061 alloy was uniform across the cross-section of the billet on the plane parallel to the extrusion direction (ED). About 70% of the total increase in hardness (up to the fourth pass) was achieved upon the first pass, and subsequent passes resulted in a near constant increase per pass. The hardness across the cross-section of the Al-6063 billet was inhomogeneous, and can be classified into three regions: top, center and bottom regions. Some of the ECAE passes resulted in decrease rather than increase in hardness at specific regions. A combination of OIM and X-ray data revealed that the decrease in hardness observed at the top region of Al-6063 billet following fourth pass was due to dynamic recrystallization. The difference in behavior exhibited by alloys Al-6061 and Al-6063 was attributed to the relative amount of manganese in the alloys. Addition of manganese in aluminum is used to increase its recrystallization temperature, and the rate of work hardening. It is evident that the little amount of manganese (< 0.05%) in Al-6063 was not enough to suppress recrystallization in the material.
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