The effect of microstructure on the deformation modes and mechanical properties of Ti-6Al-2Nb-1Ta-0.8Mo: Part II. Equiax
- PDF / 3,692,350 Bytes
- 9 Pages / 594 x 774 pts Page_size
- 79 Downloads / 193 Views
I.
INTRODUCTION
THE research described in this paper is part of a study on the effects of microstructures on the deformation modes and mechanical properties of Ti-6A1-2Nb-ITa-O.SMo (Ti-6211). To the authors' knowledge there have been no previous studies or documentation on the processing-microstructuredeformation-mechanical property relationships of Ti-6211. Part I ~ dealt with Widmanst~itten alpha + beta structures, and this paper, Part II, deals with equiaxed alpha structures and texture effects. The hexagonal alpha phase is anisotropic and this results in directionality in properties of sharply textured polycrystalline alloys containing large volume fractions of the alpha phase. 2 The magnitude of the effect depends on the degree of anisotropy in properties of the alpha phase, the morphology and relative proportions of the alpha and beta phases, and the type and sharpness of the texture. Three different types of textures are prevalent in titanium alloys: (i) random, which may be produced by beta heat treatments of alpha + beta alloys; (ii) basal, in which the basal planes are parallel to the rolling plane; and (iii) transverse, in which the basal planes are normal to the rolling plane. The 'type and sharpness of the texture obtained in a product depends on the alloy composition, the deformation schedule, and the subsequent heat treatment. There have been numerous studies of structure-property relationships in titanium alloys, but most often, with some notable exceptions,2-8 the effect of texture has been ignored. This is unfortunate since many of the thermal mechanical processing schedules which are used to change the microstructure also simultaneously alter the texture. As a result, unambiguous interpretation of much of the structure-property work that has been reported in the literature is not possible since the contribution of texture was not determined? Peters and Ltitjering6 have shown that in some inFU-SHIONG LIN is a Research Scientist, Metallurgical Research, with Reynolds Metals, Richmond, VA 23261. E.A. STARKE, Jr. is Dean and Earnest Oglesby Professor of Materials Science, School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22901. A. GYSLER is a Professor with the Department of Metallurgy, Technische Universit/it Hamburg, Hamburg, West Germany. Manuscript submitted August 26, 1983. METALLURGICALTRANSACTIONS A
stances it is possible to control texture and microstructure independently so that their individual effects may be established. In addition, commercial processing procedures for producing both basat and transverse textures have been developed by Frederick. 1~ The possibility of manipulating texture and microstructure in order to control or optimize properties is very attractive. For example, a basal texture normally gives improved biaxial strengthening compared with random and transverse textures, and may be advantageous for certain structural applications. Consequently, a description of yielding in the presence of plastic anisotropy, comparable to.the von Mi
Data Loading...
