Experimental evidence of relaxation arising from the motion of geometrical kinks on screw dislocations in iron

Progress and problems in the understanding of the dislocation relaxation processes in metals

“…␣-relaxation is now used as generic name for the intrinsic low-temperature relaxation processes in high-purity bcc metals involving dislocations. It is generally agreed that these processes comprise kink-pair generation in non-screw dislocations as well as kink migration in screw dislocations [11,12,25,[69][70][71][72]. The two types of processes may be distinguished through their 'activation volumes', which may be deduced approximately either from the amplitude dependence of the internal friction or from micro-strain experiments (see Section 1).…”

“…The two types of processes may be distinguished through their 'activation volumes', which may be deduced approximately either from the amplitude dependence of the internal friction or from micro-strain experiments (see Section 1). The small activation volumes characteristic of the relaxation processes controlled by the migration of geometrical kinks appear typically on the low-temperature side of the ␣-relaxation (e.g., in ␣-Fe below about 20 K at a measuring frequency f ≈ 1 Hz [72]). These relaxation processes are often designated as ␣ -relaxation, a practice to which we shall adhere in the following.…”