摘要
对粗晶LY 12材料进行单轴拉伸 ,在 75 3K ,应变速率为 10 - 1 s- 1 和 10 - 4s- 1 下得到大的破坏延伸率 ,而在应变速率为 10 - 2 s- 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 。
Uniaxial tensile tests were performed at 753K and large elongation to fracture were obtained at 10 -1 s -1 and 10 -4 s -1 respectively,While at 10 -2 s -1 ,10 -3 s -1 ,5×10 -4 s -1 ,the elongation to fracture were much lower.From SEM analysis,It was found wthat viscous layer is thin and grain sizes become finner duing their extruding and turning around among each others,which makes samples exhibiting good superplastic characteristics at higher strain rates.At lower strain rates,nearly all grains are covered with thick viscous layer which can optimize superplastic characteristicis as a results of grain boundary sliding.From the mechanics point of view,samples subjected to higher strain rates may fracture when tension stress is greater than the grain boundary tensile strengh so that facture surface is flatter.At lower strain rate,fracture may occur when shear stress is greater than the grain boundary shear strengh and fracture surface is rough with tearing marks.
出处
《材料科学与工程》
CSCD
北大核心
2002年第4期494-497,共4页
Materials Science and Engineering
基金
自然科学基金资助项目(1 9972 0 55)
