Ductile-brittle transition, plastics mechanical behavior

The mechanical behavior of these Be-rich phases and its variation with temperature has been studied by means of hardness tests, bending stress-rupture tests, tension tests and compression tests (Ryba, 1967 Marder and Stonehouse, 1988 Fleischer and Zabala, 1990 c Nieh and Wadsworth, 1990 Bruemmer etal., 1993). The observed brittle-to-ductile transition temperatures are of the order of 1000°C. The low-temperature fracture toughness has been found to be between 2 and 4 MN/m with practically no macroscopic ductility (Bruemmer et al., 1993), though there are indications of local plasticity at... 

The mechanical behavior of polymers is quite different from metals and ceramics and depends greatly on their structure and operating temperature. Below their glass transition temperature, Tg (the temperature at which their covalent bonded chains can no longer move relative to one another), they are quite brittle and exhibit glass-like behavior. Above their Tg, they behave plastically. In this sense, they are similar to metals that exhibit ductile-to-brittle transitions, but for entirely different reasons. 

The main considerations of mechanical properties of metals and alloys at low temperatures taken into account for safety reasons are the transition from ductile-to-brittle behavior, certain unconventional modes of plastic deformation, and mechanical and elastic properties changes due to phase transformations in the crystalline structure. 

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