【摘要】：鈦及其合金具有高的比強(qiáng)度,優(yōu)良的耐蝕性和生物相容性等優(yōu)異性能,被廣泛地應(yīng)用于航空航天、生物醫(yī)學(xué)和化學(xué)工業(yè)等領(lǐng)域。如今隨著機(jī)械工業(yè)尤其是航空航天工業(yè)的不斷發(fā)展,對鈦合金的疲勞性能提出了更高的要求。因此,表面強(qiáng)化技術(shù)得以應(yīng)用。本文通過整理多種表面機(jī)械強(qiáng)化技術(shù),分析比較了各種技術(shù)對Ti-6A1-4V表面完整性和疲勞性能的影響。同時(shí)采用超聲滾壓技術(shù)對TC4進(jìn)行了表面強(qiáng)化,并對其表面組織性能和高頻-超聲疲勞性能進(jìn)行了系統(tǒng)的測試分析。研究的結(jié)論如下。(1)超聲滾壓技術(shù)可以在不破壞試樣尺寸的基礎(chǔ)上有效降低TC4的表面粗糙度,提高表層硬度,細(xì)化表層晶粒,并在TC4表層引入了一層殘余壓應(yīng)力。(2)在高頻疲勞試驗(yàn)和超聲疲勞試驗(yàn)中,TC4超聲滾壓試樣的疲勞壽命都降低了。原因是由于超聲滾壓使TC4表層晶粒細(xì)化,表面強(qiáng)度提高,導(dǎo)致材料不均勻,從而在循環(huán)加載過程中發(fā)熱量更大,影響了疲勞壽命。(3)對TC4超聲滾壓試樣進(jìn)行真空熱處理后,表層形成更均勻的梯度結(jié)構(gòu),經(jīng)過200 ℃和300 °C處理后試樣的疲勞壽命比熱處理前稍有提高;但是當(dāng)溫度提高到400 ℃及以上時(shí),試樣的疲勞壽命大幅度降低。(4)相同應(yīng)力幅下,與超聲疲勞加載相比,試樣表面的殘余壓應(yīng)力在高頻疲勞加載過程中釋放的更快,最終殘留的壓應(yīng)力更小。
[Abstract]:Titanium and its alloys have been widely used in aerospace, biomedical and chemical industries because of their high specific strength, excellent corrosion resistance and biocompatibility. With the development of machinery industry, especially aerospace industry, the fatigue properties of titanium alloys are required. Therefore, surface strengthening technology has been applied. In this paper, the effects of various surface mechanical strengthening techniques on the surface integrity and fatigue properties of Ti-6A1-4V are analyzed and compared. At the same time, ultrasonic rolling technique was used to strengthen the surface of TC4, and the surface microstructure and high-frequency ultrasonic fatigue properties were tested and analyzed systematically. The conclusions are as follows: (1) Ultrasonic rolling technology can effectively reduce the surface roughness of TC4 without destroying the sample size, improve the surface hardness and refine the surface grain. A layer of residual compressive stress was introduced into the surface of TC4. (2) in high frequency fatigue test and ultrasonic fatigue test, the fatigue life of TC4 ultrasonic rolling specimen was decreased. The reason is that the surface grain of TC4 is refined by ultrasonic rolling, and the surface strength is increased, which leads to the uneven material, which results in more heat in the process of cyclic loading, which affects the fatigue life. (3) after the vacuum heat treatment of the TC4 ultrasonic rolling specimen, A more uniform gradient structure was formed in the surface layer, and the fatigue life of the specimen treated at 200 鈩，

本文編號：2334430