Transition single crystals, Plastic deformation

Single-crystal and poly crystalline transition metal carbides have been investigated with respect to creep, microhardness, plasticity, and shp systems. The fee carbides show slip upon mechanical load within the (111)plane in the 110 direction. The ductile-to-brittle transformation temperature of TiC is about 800 °C and is dependent on the grain size. The yield stress of TiC obeys a Hall Petch type relation, that is, the yield stress is inversely proportional to the square root of the grain size. TiC and ZrC show plastic deformation at surprisingly low temperatures around 1000 °C. 

It is widely accepted that cross slip plays a decisive role in various processes during monotonic and cyclic plastic deformation. Seeger [3] suggested that the transition to stage III in the plastic deformation of fee single crystals is governed by cross slip. Mott [4] suggested that cross slip is... 

Plastic deformation of single crystals of the transition metal oxides Mi. O with the rock-salt structure has been studied for M = Mn [43], Fe [44], Co [45-48], and... 

In addition, the nanoscratch experiments also clearly reveal the applied load necessary for the transition between elastic and plastic behavior during scratching. On unimplanted Si02 there is a long period of elastic behavior (intuitively we expect a single crystal to behave more elastically in compression than the damaged material) before the deformation becomes plastic in nature. This is then followed by a short period of plasticity before fracture (brittle) failure. The behavior on implanted... 

It is noteworthy that both elastic and plastic deformations were identified in the Ca(OH)2 structures (s = 12 m /g), which may be due to the polydispersity of the specimen. Such a dependence on the degree of dispersion can be explained as follows The range of dispersion lies between single units and tens of m /g, which corresponds to a range of crystal sizes from micrometers to tenths and hundredths of a micrometer. Based on the characteristic valnes of the density of dislocations in crystals, this range corresponds to a transition from crystals with defects (similar to macroscopic real crystals) to microcrystals with properties close to those of ideal, defect-free crystals. This is the reason why the effective microhardness (yield point) can increase considerably in the range of dispersions corresponding to the transition to submicron crystals. In the latter case, the forces that... 

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