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I.

B I D I M E N S I O N A L C O M P R E S S I O N RIGS

D E T A I L S have been published of several devices for achieving bidimensional compression. One of the earliest, by Hambly and Roscoe, t~l comprises four identical L-shaped platens, each furnished with a guide rod and a guide hole; the guide rod of any one platen slides inside the guide hole of its neighbor. More recently, Ashbee and Frank 12j have built several rigs based on four identical G-shaped platens; the leg-receiving slot of each platen accommodates the leg o f its neighbor. Here, the need to avoid binding of platens, arising from nonuniform expansion and contraction associated with temperature gradients, led us to resort to the configuration of rectangular platens shown in Figure 1. Although less satisfactory from the point of view of constraining the platens not to separate when advanced, this simpler geometry makes for easier dimensional control at temperature.

II.

EXPERIMENTAL

325-mesh samples of a commercially pure aluminum and of an age-hardening aluminum alloy were supplied by The Aluminum Company of America. The commercially pure (99.7 wt pct) aluminum sample, designated AL-123 powder, contains iron and silicon as principal impurities. The age-hardening alloy is a powder preparation of a modified 7050 or 2024 alloy, known as MB85, AI-3.7 wt pct Cu, 2.0 wt pct Mg, 0.7 wt pct Zr, 0.2 wt pct Mn. Both powders were manufactured by gas atomization. Samples from each were examined in a scanning electron microscope (Figures 2(a) and (b)). Both powders are intimate mixtures of quasi-spherical and irregular particles. The raspberrylike surface topography, particularly evident on the quasi-spheres, no doubt enhances the frictional resistance to particle rearrangement during consolidation in the predominately shear stress field created by bidimensional compression. Chemically, the S.M. JOSLIN is with the Department of Materials Science and Engineering and Center for Materials Processing, University of Tennessee, Knoxville, TN 37996-2200. K.H.G. ASHBEE, formerly Ivan Racheff Chair of Excellence, Department of Materials Science and Engineering, University of Tennessee, is with the School of Metallurgy and Materials, Faculty of Engineering, University of Birmingham, Edgbaston, Birmingham Bl5 2TT, United Kingdom. Manuscript submitted February 23, 1990. METALLURGICAL AND MATERIALS TRANSACTIONS A

particle surface layers are believed to be of a strongly adhering, hydrated aluminum o x i d e - - n o t at all the kind of surface chemistry that is likely to be conducive to particle sintering in the presence of purely compressive contacts. The outgassed powders were encapsulated in aluminum cans closed at one end and supplied by the Pearless Tube Company (Bloomfield, NJ). Before introducing the powder, each can was drawn through a square orifice that matched the cross section to that of the confined cell defined by the compression platens. Squared end caps were, in some experiments, welded into position and in other experiments, secured by mechanical fasteni