材料期刊网

在稀铝铜和稀铝镁合金中于室温附近观测到低频振幅内耗峰和温度内耗峰,所用的最大表面应变振幅为5×10~(-7)—1×10~(-3).这种反常内耗表现出一种特殊的时效行为.与此同时,还观测到时效内耗峰,曾在下列三种条件下反复观测到这些内耗峰: (1)高度冷加工的试样退火到刚在完全再结晶以前;(2)充分退火的试样冷加工到刚超过屈服;(3)充分退火的试样经高温淬火.业已证明,观测到的这些内耗峰是由溶质原子(Al中的Cu或Mg)与冷加工或淬火产生的“新鲜”可动位错之间的交互作用引起的.这种新鲜位错含有大量弯结.提出了一种改进了的位错气团模型,认为当位错弯结在外加交变应力作用下作往复沿边运动的过程中,溶质原子被拖着在两个势垒之间来回移动.

Low-frequency "amplitude peaks" and "temperature peaks" were observed inthe internal friction of dilute Al-Cu nd Al-Mg alloys around room temperature ata maximum surface-strain amplitude ranging from 5×10~(-7) to 1×10~(-5). This nom-alous internal friction showed a peculiar aging behaviour. An aging peak wasobserved in conjunction with the mplitude eak and the temperature peak. Suchpeaks have been observed repeatedly in: (1) heavily cold-worked specimens an-nealed ust rior to complete recrystallization; (2) fully annealed specimens cold-worked just after yielding; (3) fully annealed pecimens quenched from anelevated temperature. It is shown that the observed internal friction is associated with the nterac-tion of solute atoms (Cu and Mg in Al) with the mobile "fresh" dislocations pro-duced by cold-work or quenching. uch fresh dislocations contain a large numberof kinks. A modified dislocation atmosphere model was suggested in which thesolute atoms are assumed to be dragged along between two potential valleys dur-ing the to and fro sidewise motion of a ink under the action of the appliedalternating stress.