TC6钛合金激光喷丸纳米组织特性及热稳定性研究(英文)

应用Nd:YAG高功率激光器对TC6钛合金试样进行了激光喷丸,对部分强化试样623K真空保温10h。应用原子力显微镜(AFM)、扫描电镜(SEM)、电子背散射电镜(EBSD)、X射线衍射(XRD)、透射电镜(TEM)等设备对试样强化层形貌和纳米组织进行检测,采用显微硬度计进行显微硬度测量。测试结果表明:TC6钛合金激光喷丸表面完整性好,未在表面引入微裂纹,表面粗糙度较传统表面强化低;激光喷丸后距离表面200μm范围内α相在冲击波作用下压缩伸长,α相和β相细化,保温后SEM测试显示强化层组织和强化层深度未发现明显变化;强化后衍射峰变宽,说明强化层发生剧烈塑性变形导致晶粒细化,并留有残余应变,未发现新的衍射峰说明强化过程中没有发生相变;强化后TC6钛合金表层产生纳米晶,保温后强化层位错密度降低,纳米晶晶界更加清晰,未发现纳米晶长大;激光喷丸硬度影响层达500μm,表面硬度提高12.2%,保温后表面显微硬度降低10HV0.5,硬化深度未发现变化。以上研究表明,TC6激光喷丸纳米组织和显微硬度在623K温度下具有较好的热稳定性,有利于提高钛合金的抗疲劳、抗磨损和抗应力腐蚀的性能,从而突破了美国规范AMS2546中关于钛合金只能在589K温度下应用的限制。

PROPERTY AND THERMOSTABLITY STUDY ON TC6 TITANIUM ALLOY NANOSTRUCTURE PROCESSED BY LSP

TC6 titanium alloy samples are processed by laser shock peening(LSP).Then,some samples are vacuum annealed at 623 K for 10 h for the study on the thermostablity of the nanostructure produced by LSP.The characteristics of the strengthened layer and nanostructure are studied by atomic force microscopy(AFM),scanning electron microscope(SEM),electron backscatter diffraction(EBSD),X-ray diffraction(XRD),and transmission electron microscopy(TEM)appliances,meanwhile the enhanced microhardness is tested at cross section.AFM of the processed surface indicates that the deformation is approximately uniform,and LSP slightly increases the roughness.SEM and EBSD of the strengthened cross section show that α phases are compressed to strip-shaped,a proportion of α and β phases is shattered to smaller phases from surface to 200 μm in depth.The surface XRD shows that although there is no new produced phase during LSP,the grain size refinement and the introduction of lattice micro-strains lead to the broadened peak.The TEM photographs and diffraction patterns indicate that the shock wave provides high strain rate deformation and leads to the formation of nanocrystal.Compared with the samples before annealing,the dislocation density is lower and the grain-boundary is more distinct in the annealed samples,but the nanocrystal size does not grow bigger after annealing.The microhardness measurement indicates that LSP improves the microhardness of TC6 for about 12.2% on the surface,and the layer affected by LSP is about 500 μm in depth.The microhardness after annealing is 10 HV0.5 lower,but the affected depth does not change.The thermostable study shows that the strengthened layer of TC6 processed by LSP is stable at 623 K.The strengthened thermostable layer can significantly improve the fatigue resistance,wear resistance and stress corrosion resistance of the titanium alloy.The study results break the USA standard AMS2546 that titanium parts after LSP are subjected in subsequent processing within 589 K.