双晶铝晶界驰豫起始温度的滞弹性测量

Anelastic Micro-creep Studies of Temperature Dependence ofthe Grain-boundary Relaxation in Aluminium Bicrystals

测量了夹角分别为１０°和５０．５°的［１１０］对称倾侧铝双晶晶界的扭转滞弹性蠕变曲线，得到了晶界的弛豫强度约在０．４２Ｔ＿ｍ温度时变为零（Ｔ＿ｍ为铝的熔点温度），进一步肯定了晶界的内部结构在这个温度的附近发生了显著的变化。同时，采用“晶界附近位错亚结构连续分布与晶界原子的交互工作用模型”，对双晶晶界的驰豫机制做了合理地解释。

The stability of grain-boundary structure at high temperature has long been a problem in dispute.The main point of this dispute is whether the grain-boundary can melt into a structure similar to that ofsuper-cooled liquid or becomes disordered at a temperature T￣0 much lower than the bulk melting pointT_0. In this paper, anelastic creep curves of[110] symmetrical tilt boundaries with mis-orientation an-gles 10￣0 and 50. 5￣0 in aluminium bicrystals have been measured in torsion. The variation of relaxationstrength (Δ) with temperature(T) of measurements and the temperature at which the unrelaxed compli-ance J_u begin to deviate from a straight line relationship were determined. The results show that thegain-boundary relaxation strength (Δ)decreases with lowering temperature and drops to zero at a tem-perature T_0 which are 0. 42T_m and 0. 41T_m for 10￣0 and 50. 5￣0 angles respectively,where T_m is the melt-ing point of bulk aluminium. Around this temperature T_0 point , the J_u-T curve deviate from a straightline relationship which is the behaviour of single aluminium crystal. These indicate that a perceptiblechange of the internal structure of the gainboundary has taken place around this temperature. Theseexperimental results are agreement with that of the molecular dynamics simulation using atomic inter-action potential. It is assumed that the micro-mechanism of bicrystal srain-boundary relaxation is theinteraction of grain-boundary with nearby continuous distributed dislocation substructures.