1063-7834/03/4507- $24.00 © 2003 MAIK “Nauka/Interperiodica” 1267 Physics of the Solid State, Vol. 45, No. 7, 2003, pp. 1267–1271. Translated from Fizika Tverdogo Tela, Vol. 45, No. 7, 2003, pp. 1209–1212. Original Russian Text Copyright © 2003 by Golovin, Ivolgin, Tyurin, Khonik. 1. INTRODUCTION Although plastic deformation is always atomically inhomogeneous (contrary to elastic deformation), the physics of plasticity recognizes homogeneous and inhomogeneous flow modes [1–7]. A conventional boundary between these modes is mainly specified by the test temperature T ; strain rate ; and history, size, and state of the surface of a sample [2, 5, 8–14]. The position of this boundary depends substantially on the characteristics of the testing machine, in particular, its stiffness, response time, and sensitivity to changes in the deforming force or in the sample size. Traditional equipment, such as an Instron testing machine, makes it possible to record only relatively large jumps of mac- roscopic deformation with low repetition frequency appearing due to the collective behavior of a huge num- ber of elementary carriers of plastic deformation, while the other possible instabilities of a flow remain unde- tected. As a result, the statistics of detected jumps are scarce and not representative and the contribution from jumps to the total stored deformation is strongly under- estimated. To study the dynamics and correlation of deforma- tion jumps on a smaller spatial scale (in particular, on the mesoscopic scale), it is necessary to substantially increase the space–time resolution of the equipment and to decrease the sample volume. A higher resolution is also required to analyze the instabilities of a plastic flow in the context of the theory of self-organization in nonequilibrium dissipative media (to which plastically deformed solids belong), since the number of recorded jumps should increase under these conditions and cor- relation relations between them will be more apparent. In this work, we used depth-sensing testing to obtain the dependence of the load P on the indentation depth h (an analog of the σ = f(ε) diagram for uniaxial deforma- tion) and the P(t) and h(t) time dependences for submi- cron regions. The limiting resolutions of modern com- ε ˙ mercial nanoindentometers are 0.1 nm for the indenta- tion depth, several micronewtons for the load, and 10 –2 s for the time, which are several orders-of-magnitude higher than those of the standard testing machines. This performance allows one to study fine and rapid jumps, as well as to extend the range of strain rates toward higher values of (since ≈ dh/hdt and h can be 1 μm during depth-sensing testing) and to work on one sam- ple. Apart from these advantages, the factors mentioned above can serve to establish the boundaries of the size- strain-rate invariance for stable and unstable flow modes in nanoscale samples. Pioneering studies [15–17] on the serrated deforma- tion by nanoindentation were carried out several years ago and dealt with an unstable flow in fcc metals and polycrystalline aluminum–magnesium alloys that had been previously well studied using the methods of mac- rodeformation [18, 19]. Related information for amor- phous alloys is limited, as far as we know, to papers [20, 21], in which multiple deformation nanojumps were detected during local deformation of a palladium-based bulk amorphous alloy by using nanoindentation. Macroscopic measurements [4] show that, at mod- erate strain rates (10 –5 ≤ ≤ 10 –3 s –1 ) and temperatures T < 400 K, a flow is localized, whereas at higher tem- peratures the flow becomes uniform. The transition is assumed to be due to the equalizing of the strain rates and a directed structural relaxation [4, 5, 12, 13]. It is obvious that, at room temperature, this transition is characterized by a very low critical strain rate , which cannot be achieved under the conventional con- ditions of active deformation. On the other hand, Kimura and Masumoto [22] showed that, at ~ 0.1 s –1 , the reverse transition (from inhomogeneous to homoge- neous flow) can proceed; the nature of this reverse tran- sition was not discussed. ε ˙ ε ˙ ε ˙ ε ˙ c ' ε ˙ c '' Serrated Deformation of a Pd 40 Cu 30 Ni 10 P 20 Bulk Amorphous Alloy during Nanoindentation Yu. I. Golovin*, V. I. Ivolgin*, A. I. Tyurin*, and V. A. Khonik** * Derzhavin Tambov State University, Tambov, 392622 Russia e-mail: golovin@tsu.tmb.ru ** Voronezh State Pedagogical University, ul. Lenina 86, Voronezh, 394611 Russia Received November 1, 2002 Abstract—Depth-sensing (indentation) testing is used to study the characteristics of a serrated plastic flow in a Pd 40 Cu 30 Ni 10 P 20 bulk amorphous alloy, and the boundaries between the regions of serrated and homogeneous plastic deformation are determined. © 2003 MAIK “Nauka/Interperiodica”. DEFECTS, DISLOCATIONS, AND PHYSICS OF STRENGTH