表面纳米梯度对热轧态Ti-6.5Al-2Zr-1Mo-1V合金组织与性能的影响

The Effect of Surface Nanogradient on the Microstructure and Properties of hot-rolled Ti-6.5Al-2Zr-1Mo-1V Alloy

摘要:

为解决钛合金结构件表面腐蚀疲劳造成的失效问题，延长钛合金材料作为飞机结构件的使用寿命。采用超音速微粒轰击（SFPB）技术对热轧态Ti-6.5Al-2Zr-1Mo-1V（TA15）合金进行不同时间的冲击，在试样表层构筑梯度纳米结构，借助各种仪器设备研究不同时间处理后对显微组织、微观形貌及力学性能的影响。在SFPB处理时间为60 s时，热轧态组织的表层平均纳米晶粒尺寸最小，为30.4 nm。处理后试样表面粗糙度相较于原始试样有所增加，时间为60 s时，表面粗糙度最小，而更长时间的冲击会导致试样表面产生微裂纹。SFPB处理在试样表面引入高幅的残余压应力，试样显微硬度明显提升。SFPB处理后试样的强度提高，延伸率略微下降后趋于稳定。在处理时间为60 s时，可以得到最佳的强-塑性综合匹配。SFPB处理后试样的腐蚀疲劳寿命相较于未处理试样提升了12.7倍。SFPB处理能够在TA15钛合金近表面获得梯度纳米层，显著提高TA15钛合金拉伸性能和腐蚀疲劳寿命。

Abstract:

To address the failure caused by surface corrosion fatigue of titanium alloy structural components and to extend the service life of titanium alloys used in aircraft structures, Supersonic fine particle bombardment (SFPB) technology was applied to the hot-rolled Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy with varying impact times. This process created a gradient nanostructure on the surface of the samples, and various instruments and equipment were used to study the effects on the microstructure, microscopic morphology, and mechanical properties after different treatment times. At an SFPB treatment time of 60 s, the surface average nanocrystal grain size of the hot-rolled structure was minimized, measuring 30.4 nm. The surface roughness of the treated samples increased compared to the original ones, with the minimum surface roughness occurring at 60 s. However, longer impact times led to the formation of microcracks on the sample surface. The SFPB treatment introduced high compressive residual stress on the sample surface, resulting in a significant increase in microhardness. After the SFPB treatment, the sample"s strength increased, with a slight decrease in elongation before stabilizing. At a treatment time of 60 s, the best combination of strength and plasticity was achieved. The corrosion fatigue life of the SFPB-treated samples was improved by 12.7 times compared to the untreated samples. The SFPB treatment was able to generate a gradient nanolayer near the surface of the TA15 titanium alloy, significantly enhancing its tensile properties and corrosion fatigue life.