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純鈦及鈦合金的強流脈沖電子束表面改性研究

發(fā)布時間:2018-10-30 21:08
【摘要】:強流脈沖電子束技術是近年來發(fā)展起來的一項新興材料表面改性技術,而軋制是在上世紀發(fā)展起來的金屬形變技術。本文將軋制技術和強流脈沖電子束技術相結合,并選擇純鈦TA2及TC2、TC4鈦合金進行復合處理,研究了這幾種材料表層微結構、相組成、硬度和抗腐蝕性能在處理前后的變化,主要研究結果如下:1、在電子束處理過程中,純鈦和TC2、TC4鈦合金表層都發(fā)生了α向β再向α’的馬氏體轉變。電子束處理后,純鈦及鈦合金表面形成大量火山坑,而隨著電子束脈沖次數(shù)的增加,火山坑密度呈現(xiàn)出減少的趨勢。2、電子束處理也使得表層晶粒出現(xiàn)了擇優(yōu)取向,XRD分析顯示α(002)、α(101)晶面衍射強度不斷降低,而α(100)晶面衍射強度逐漸增強。3、軋制對純鈦及TC2、TC4鈦合金起到了形變強化的作用,而電子束處理使得純鈦及TC2、TC4鈦合金的表面硬度下降,主要是因為脈沖電子束處理消除了表面殘余應力及生成的馬氏體硬度較低的緣故。4、軋制及電子束處理能提高純鈦的抗腐蝕性能,隨著變形率的增加、抗腐蝕性能逐漸增加,當軋制變形率為70%時,抗腐蝕性能最好。當純鈦變形率一定時,脈沖次數(shù)為5次時,純鈦抗腐蝕性能最好。在電子束5次脈沖處理時,隨著變形率的增加,純鈦抗腐蝕性能愈來愈好,變形率為70%,電子束轟擊次數(shù)為5次時,腐蝕電流密度為245.3 m A/cm2。這主要是因為軋制的大塑性變形使得純鈦晶粒得到充分細化,當脈沖次數(shù)過多時,反而引起晶粒的長大,降低純鈦的抗腐蝕性能。5、TC4鈦合金在軋制加脈沖電子束處理后,材料的抗腐蝕性能大幅提高,電子束分別轟擊TC4鈦合金5次,10次后,自腐蝕電位較基體的-682.5m V分別增加到-297.5m V、-342.3 m V。而腐蝕電流密度也由基體的1028.1m A/cm2減少到電子束5次脈沖處理時的382.0 m A/cm2。TC2鈦合金自腐蝕電位從電子束處理前的-625.7 m V升高到10次脈沖的-163.5m V,而5次脈沖處理后,腐蝕電流密度減少到了343.3 m A/cm2。表明電子束對TC4、TC2鈦合金處理后,5次脈沖時抗腐蝕性能最好,晶粒細化、相組成均一化和表面凈化是材料表面腐蝕性能提高的主要原因。
[Abstract]:High current pulsed electron beam technology is a new material surface modification technology developed in recent years, and rolling is a metal deformation technology developed in the last century. In this paper, the rolling technology and high current pulsed electron beam technology are combined, and pure titanium TA2 and TC2,TC4 titanium alloys are selected for composite treatment. The changes of surface microstructure, phase composition, hardness and corrosion resistance of these materials before and after treatment are studied. The main results are as follows: 1. In the process of electron beam treatment, both pure titanium and TC2,TC4 titanium alloys undergo a transformation from 偽 to 尾 to 偽 'martensite. After electron beam treatment, a large number of volcanic craters were formed on the surface of pure titanium and titanium alloys, and the density of volcanic pits decreased with the increase of the number of electron beam pulses. XRD analysis showed that the diffraction intensity of 偽 (002), 偽 (101) plane was decreasing, while the diffraction intensity of 偽 (100) plane was gradually increasing. 3. Rolling had the effect of strengthening the deformation of pure titanium and TC2,TC4 titanium alloy. However, the surface hardness of pure titanium and TC2,TC4 titanium alloy was decreased by electron beam treatment, which was mainly due to the elimination of surface residual stress and the lower hardness of martensite formed by pulsed electron beam treatment. Rolling and electron beam treatment can improve the corrosion resistance of pure titanium. With the increase of deformation rate, the corrosion resistance increases gradually. When the rolling deformation rate is 70, the corrosion resistance is the best. When the deformation rate of pure titanium is constant and the pulse number is 5 times, the corrosion resistance of pure titanium is the best. When the electron beam was treated with 5 pulses, the corrosion resistance of pure titanium increased with the increase of deformation rate. The corrosion current density of pure titanium was 245.3 Ma / cm ~ 2 when the electron beam bombardment times were 5 times and the deformation rate was 70 times. This is mainly due to the large plastic deformation of rolling, which makes the grain of pure titanium fully refined. When the pulse number is too many, the grain will grow up, and the corrosion resistance of pure titanium will be reduced. 5% TC4 titanium alloy after rolling with pulsed electron beam treatment, The corrosion resistance of the material was greatly improved. After 5 times of electron beam bombardment on TC4 titanium alloy, the self-corrosion potential increased from -682.5mV to -297.5m V ~ (-1) -342.3 MV, respectively. The corrosion current density decreased from 1028.1 A/cm2 of substrate to 382.0 m A/cm2.TC2 of titanium alloy treated by electron beam for 5 times. The corrosion potential of titanium alloy increased from -625.7 MV before electron beam treatment to -163.5m V with 10 pulses. After five pulse treatments, the corrosion current density decreased to 343.3 Ma / cm ~ 2. The results show that the corrosion resistance of TC4,TC2 titanium alloy treated by electron beam is the best after 5 pulses, the grain is fine, the phase composition is homogenized and the surface purification is the main reason for the improvement of the surface corrosion performance of the material.
【學位授予單位】:上海工程技術大學
【學位級別】:碩士
【學位授予年份】:2015
【分類號】:TG174.4

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