DEFORMATION PROCESSING OF ANISOTROPIC METALS.
Final rept. 1 Jul 68-30 Jun 69,
MASSACHUSETTS INST OF TECH CAMBRIDGE METALS PROCESSING LAB
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An account is given of the development of a process for using superplasticity in forming. Its focus is necessarily specific, but there is general value in its findings. The actual parts were examples of hollow ware that had once been produced by conventional methods. The material was the Zn-Al eutectoid alloy, which can be made highly superplastic and should give adequate service behavior for a variety of applications, including this one. The development proceeded by first separating the total process into two largely dissimilar components stretching, to establish general shape macroforming, and another, more related to coining, to generate surface detail microforming. The results of the separate studies were finally combined to allow predictions of the outcome of practical forming. These, in turn, were tested experimentally with good success. Of the two components, microforming is more often likely to be pressure- and rate-controlling. An analysis is presented for the bulging by lateral pressure of superplastic alloy sheet that has a flow equation in uniaxial tension or compression. Two cases are dealt with 1 the bulging of a flat circular sheet clamped at its perimeter and 2 the bulging of a sheet into 90 degree-V grooves. The latter process is pertinent to the problem of molding a sheet to a die contour so as to achieve detail. Bulge profile and sheet-thickness distribution are predicted as a function of the variables, pressure, geometry, time, K and m. Author
- Fabrication Metallurgy