Simulation of solid lubricants and contact spots between bridgman anvils Part II. Experimental results on f.c.c. metals and new insights gained

• Published in: Wear Vol. 149; no. 1; pp. 279 - 296
• Main Authors: Cai, B.C., Kuhlmann-Wilsdorf, D., Nelson, R.B.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.1991
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/0043-1648(91)90380-D

By means of the instrumentation described in Part I stress-strain curves have been obtained for technically pure aluminum, copper, silver and gold under pressures up to 4000 MPa (40 kbar). Measured values for the shearing stress and its pressure dependence are largely at variance with the sparse and mutually contradictory prior data in the literature. The discrepancies are partly explained through previously undiscovered anvil-sample slippage and/or sample perforation and consequent anvil-anvil contact. Results so far lead to the following conclusions: 1. (i) Ordinary dislocation glide operates. 2. (ii) No intrinsic upper limit to shear strain exists. 3. (iii) The Peierls-Nabarro stress dominates the flow stress at high pressures. 4. (iv) During distributed shearing, samples continue to thin and sample material is squeezed out, which implies that solid lubricants will be similarly squeezed out. 5. (v) A limiting thickness and/or sample perforation trigger “turbulent flow” with increased flow stress. 6. (vi) Turbulent flow can lead to mechanical alloying and this can give rise to glassy layers. 7. (vii) The enumerated phenomena are also expected in normal sliding between interfaces with or without solid lubrication.