论文部分内容阅读
为了研究激光喷丸对IN718镍基合金微观组织特性的影响及其在高温下的稳定性,首先在常温下对标准拉伸试样关键区域进行激光喷丸处理,随后将喷丸样置于700℃下保温300 min,作为对比,分别测试了未喷丸样、喷丸样和喷丸高温保持样的表层残余应力和纳米硬度,并采用光学电镜和透射电镜对其微观组织特征进行观测。结果表明,激光喷丸后试样的表层出现了高幅值的残余压应力,最高值出现在喷丸中心,约为-706 MPa;激光喷丸后试样的表层硬度显著提高,平均纳米硬度提高了约67.4%;高温保持后试样的残余应力和纳米硬度均有不同程度的降低,但与未喷丸试样相比,强化增益效果仍然存在;显微组织观察结果显示,激光喷丸后,试样深度方向上晶粒形态均出现了显著的“分层”现象,塑性变形层晶粒细化明显,其影响深度可达80μm;保温后喷丸样晶界处可见析出条状δ相;TEM图像进一步表明,激光喷丸诱导的晶粒细化是条状孪晶和位错组织混合交织的结果;保温后喷丸样晶界处发现了沿同一方向向晶内延伸的位错阵列,这很好地验证了位错在高温下的活性,且是激光喷丸抑制晶粒在高温下快速增长的直接证据。
In order to study the effect of laser shot peening on the microstructure and properties of IN718 Ni-based alloy and its stability at high temperature, laser shot peening was first performed on the key tensile specimens at normal temperature, ℃ for 300 min. The residual stress and nanohardness of the non-shot-peening, shot-peening and shot-peening were tested respectively. The microstructure of the samples was observed by optical and transmission electron microscopy. The results show that there is a high compressive residual compressive stress on the surface of the specimen after laser peening, the highest value appears at the center of the shot peening, which is about -706 MPa. The surface hardness of the sample after laser peening obviously increases, the average nanohardness Which is about 67.4% higher than that of the control. The residual stress and the nanohardness of the sample after the high temperature maintenance are reduced to some extent, but the enhancement gain effect still exists compared with the non-shot sample. The microstructure observation shows that the laser shot peening , The grain morphology in the depth direction of the sample all showed significant “stratification” phenomenon. The grain deformation of the plastic deformation layer was obvious and the influence depth was up to 80μm. TEM images further show that the grain refinement induced by laser shot peening is the result of mixed interlacing of strip twins and dislocations. After the shot peening at grain boundaries, Dislocation arrays, which well verify the activity of dislocations at high temperatures and are direct evidence that laser shot peening suppresses the rapid growth of grains at high temperatures.