二次孔擠壓強(qiáng)化對(duì)TB6鈦合金疲勞性能的影響

二次孔擠壓強(qiáng)化對(duì)TB6鈦合金疲勞性能的影響Effect of Double Cold Expansion of Hole on Fatigue Property of TB6 Titanium Alloy

為了提高TB6鈦合金耳片孔的疲勞抗力，研究二次孔擠壓強(qiáng)化對(duì)TB6鈦合金耳片孔試樣疲勞壽命的影響，采用掃描電鏡、粗糙度儀、X射線衍射儀、顯微硬度計(jì)及金相顯微鏡等儀器對(duì)孔壁表面完整性進(jìn)行分析，探討二次孔擠壓強(qiáng)化對(duì)疲勞壽命的增益機(jī)制。結(jié)果表明：相比過盈配合試樣，二次孔擠壓強(qiáng)化耳片孔試樣的軸向拉伸疲勞壽命顯著提高；經(jīng)二次孔擠壓強(qiáng)化后，孔壁表面完整性得到了顯著改善；孔壁表面粗糙度顯著下降；表層晶粒組織發(fā)生了明顯的塑性變形；顯微硬度顯著提高；形成了較深的殘余壓應(yīng)力場(chǎng)和組織強(qiáng)化層；孔壁表面完整性的改善對(duì)微動(dòng)疲勞壽命的增益具有重要作用。

To improve the fatigue resistance of the bolt connecting hole, the effect of double cold expansion (DCE) of the hole on the fatigue life of TB6 titanium alloy was investigated. The fatigue fracture, surface roughness, residual stress, hardness and microstructure of the hole wall were characterized by scanning electron microscopy (SEM), roughmeter, X-ray diffraction (XRD), microhardness tester and optical microscopy. The mechanism of DCE on the fatigue life of the hole was also investigated. The results show that the mean value of the fatigue life of DCE specimen is much higher than that of the interference fit specimen. The surface integrity of the hole wall is improved after DCE. The roughness decreases remarkably. The deep surface-strengthen-layer with high hardness and deep residual compressive stress field are formed around the hole through severe plastic deformation of the microstructure of the hole wall. It is considered that the improvement of surface integrity plays an important role on the enhancement of fretting fatigue life.

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