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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Influence of hot rolling microstructure on mechanical properties of fullyannealed 5052 aluminum alloy

Hung, Liang-Jie 24 July 2012 (has links)
The objective of this work is to investigate the influence of hot rolling process on the mechanical properties of AA 5052 aluminum alloy. Hot-rolled band fabricated by tandem mill (hot-band A) will be compared with that fabricated by reverse mill hot-band C). Optical microscopic observations revealed that hot-band A has a uniform microstructure throughout the thickness, while hot-band C exhibits non-uniform microstructure, fine grains near the surface and coarser grains in the center. Both hot-bands were subjected to cold-rolling and annealing to O-temper. Two annealing processes were used: (a) annealing in 500oC salt bath, which may simulate the high heating rate of continuous annealing line (CAL), and (b) annealing in 320oC conventional air furnace with heating rate of 30oC/h, which may simulate the slow heating rate of batch-type annealing. In general, both materials annealed in 320oC air furnace exhibit higher yield strength than those annealed in 500oC salt bath do, however, both materials exhibit better tensile ductility after annealed in 500oC salt bath as compared with those annealed in 320oC air furnace.TEM examinations indicated that the cold-rolled sheet after annealing in 320oC air furnace contains larger number of precipitates comparing with its 500oC salt bath annealed counterpart. This observation may account for the higher yield strength of cold-rolled sheet annealed in 320oC air furnace. After cold-rolling and annealing in 320oC air furnace, the material C shows higher yield strength than the material A does. However, after annealing in 500oC salt bath, both materials have similar yield strength. XRD pole-figure analysis indicated that hot-band A exhibited stronger texture than hot-band C did. The texture intensity for both materials decreased considerably after cold-rolling and annealing. Orientation image mapping (OIM) obtained by EBSD (electron backscattered diffraction) analysis indicated that the grain boundaries in both materials after cold-rolling and annealing were mainly high angle boundaries, and the 500oC salt bath annealed specimens have more equiaxed grain shape as compared with the 320oC air furnace annealed specimens.

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