喷丸强化DD6单晶合金中温单轴拉伸性能

One-axis Tensile Property of Shot-peened DD6 Single Crystal Superalloy

为研究喷丸对单晶合金中温拉伸性能影响,采用陶瓷弹丸对DD6单晶合金(后简称单晶)进行喷丸,研究了[001]取向单晶原始/喷丸后600、650和850℃的单轴拉伸性能。采用显微硬度和透射电镜分析了喷丸单晶表层组织,并采用扫描电镜观察了拉伸断口。结果表明:喷丸对单晶中温抗拉、屈服强度及850℃拉伸塑性无影响,而喷丸后单晶的600和650℃拉伸塑性显著下降。650℃时,延长率和断面收缩率分别由16.1%和20.1%下降到喷丸后的3.8%和6.9%;600℃时,延长率和断面收缩率分别由10.5%和18.4%下降到喷丸后的2.8%和7.5%。喷丸单晶表面形成了以{111}交叉滑移孪晶面,与600和650℃拉伸主滑移面重合,孪晶使得拉伸过程进一步表面变形困难,内部金属变形受到限制,表现为喷丸单晶600和650℃拉伸塑性下降。单晶850℃拉伸过程中,除开动八面体滑移外,还开动了六面体滑移,未出现喷丸孪晶面与拉伸主滑移面重合问题,故喷丸不影响850℃单晶拉伸塑性。

To research the influence of shot peening on the mechanical property of the single crystal superalloy at the medium temperature, ceramic shot was employed to peen the DD6 single crystal superalloy(SX) to investigate one-axis tensile properties at 600, 650 and 850℃, compared with that of the as-received alloy. Surface integrity of shot-peened SX was characterized using micro-hardness test and TEM, and tensile fractures were observed by SEM. Results show that shot peening has no obvious effect on the tensile strength, yield strength and tensile plasticity at 850℃. However, tensile plasticity at 600 and 650℃ significantly declines after peening. At 650℃, the average elongation and cross-section shrinkage rate after peening fall from 16.1% and 20.1% to 3.8% and 6.9%, respectively, while the two properties at 600℃, go down from 10.5% and18.4% to 2.8% and to 7.5%, respectively.{111} interlaced-line-type twins are formed by shot peening, which is close to the tensile fracture surface, i.e, the glide plane at 600℃ and 650℃. During the tensile process, the twins further make surface metal deformation difficult and also restrict the slippage of the inner metal, which express the phenomena of the 600℃ and650℃ tensile plastic of peened SX descending. During the process of 850℃ tension, not only octahedron glide but hexahedron glide occurres. Furthermore, there is no coincidence between shot peening twin plane and main glide surface in tension.Therefore, shot peening does not affect the tensile plasticity of SX at 850℃.