DEFORMATION PROCESSING OF ANISOTROPIC METALS.
MASSACHUSETTS INST OF TECH CAMBRIDGE METALS PROCESSING LAB
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Titanium of commercial purity RC-70 and two allalpha HCP alloys 4Al-1402 and 5Al-2.5Sn were tested in sheet form under conditions of combined-stress loading. Plane-strain compression and plane-strain tension together with uniaxial compression and tension provided information for constructing the tension-tension and compression-compression quadrants of the plane-stress yield locus. The deformation of textured sheet of titanium and several of its all-alpha HCP alloys was investigated with basically two kinds of experiments tension testing along different directions in the plane of the sheet and combinedstress loading along principal axes of anisotropy the rolling and transverse directions. Texture and plastic anisotropy were evaluated with pole figures and by measurement, as a function of orientation, of the tensile transversestrain ratio, or R parameter. A phenomenological explanation of superplasticity in metals has been based on the observation of a strong strain-rate dependence of flow stress, comparable to that of heated polymers and approaching that of hot glass. A structural basis for such high rate sensitivity is suggested in the present paper. It is argued that at temperatures about 0.5T sub m two competitive processes contribute to deformation.