The presence of small amount of liquid at grain boundaries tends to form thin viscous layer which surrounds the finer grains . intergranular fracture may occur at the grain boundaries between two fine grains not covered by viscous phases . the high ductility achieved at low strain rates is generally attributed to dislocation glide - creep accommodation mechanisms 原始晶界上產生少量液相,形成薄的固液共存粘性層并包圍細化的晶粒,沿晶斷裂主要發生在無粘性層的細晶粒間;而在較低應變速率下,三叉晶界位錯攀援?蠕變協調機制松弛晶界滑移產生的應力集中,晶界上產生較多液相,有利于晶界滑移進行。