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The development of textures and microstructures in alpha/beta titanium alloys

Bhattacharyya, Dhriti

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2004, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
The relationship between the texture and the microstructure of both beta processed and alpha/beta processed Ti alloys has been examined in this study. In the beta-processed microstructures, it has been shown that two sets of alpha colonies sharing a common {0001} plane and rotated by ~10.5° from each other may have growth directions which have very large angles of about ~80.7° between them. Moreover, it was observed that alpha laths growing from certain prior beta grain boundaries sometimes shared common basal planes. In some special cases, the alpha laths growing into two different prior beta grains from the grain boundary between them had almost exactly the same orientation, although they had vastly different growth directions. Additionally, there were some cases in which alpha laths growing into different prior beta grains not only had the same crystallographic orientation, but also had the same growth direction. Scanning Electron Microscopy (SEM), Orientation Imaging Microscopy (OIM) and Transmission Electron Microscopy (TEM) have been used to investigate these phenomena and the existing theories of growth directions have been used in conjunction with the results obtained to explain them. In alpha/beta-processed alloys, the phenomenon of globularization of alpha laths breaks down the beta-processed microstructure and modifies the texture of these alloys. Samples of Ti-6Al-4V having colony and basketweave microstructures were hot deformed in the high alpha/beta temperature range and their microstructure and microtexture were examined by the use of SEM and OIM. It is shown that the samples which had a colony microstructure had greater “clustering” of grains with similar orientations than those having a basketweave microstructure. The mode of transformation on heating from the alpha to the beta phase was investigated by measuring the texture of both phases at different temperatures, in situ, using the HIPPO instrument at the Los Alamos Neutron Science Center. A comparison of the pole figures for both phases has allowed an insight into the mode of transformation of the alpha to the beta phase, and it appears that the beta phase forms by the growth of the preexisting beta, and not by fresh nucleation of beta in the alpha phase.
Hamish Fraser (Advisor)

Recommended Citations

Citations

  • Bhattacharyya, D. (2004). The development of textures and microstructures in alpha/beta titanium alloys [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1086195557

    APA Style (7th edition)

  • Bhattacharyya, Dhriti. The development of textures and microstructures in alpha/beta titanium alloys. 2004. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1086195557.

    MLA Style (8th edition)

  • Bhattacharyya, Dhriti. "The development of textures and microstructures in alpha/beta titanium alloys." Doctoral dissertation, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1086195557

    Chicago Manual of Style (17th edition)