对粗晶LY-12材料进行单轴拉伸,在753K,应变速率为10-1s-1和10-4s-1下得到大的破坏延伸率,而在应变速率为10-2s-1、10-3s-1、5×10-4s-1时的破坏延伸率较小.断口SEM分析表明,高应变速率下,晶界 上的粘性层很薄,在晶粒的相互挤压和转动中很容易细化,使材料的超塑性变形能力增强;低应变速率下,晶界上粘性层厚度增大,晶粒被厚的粘性物质包围,使晶界滑移更容易进行,超塑性变形能力也会增强.处于中间应变速率下,晶粒没有足够细化,粘性层也不够厚,所以超塑性变形能力略低.从力学角度解释断裂机制,高应变速率下,当晶粒间的正应力大于晶界的结合强度时导致断裂,断口表面平齐;应变速率较低时,晶界面的剪应力大于晶界的剪切强度导致断裂,断口有撕裂的齿牙状特征,较为粗糙.
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