不同相组成近β钛合金Ti-3Al-5Mo-4Nb-4Cr-2Zr的应力腐蚀行为  

Stress Corrosion Behavior of Near-βTitanium Alloy Ti-3Al-5Mo-4Nb-4Cr-2Zr with Different Phase Composition

作　　者：王川[1,2] 张浩宇 陈立佳[1] 周舸[1] 程军 张思倩[1] Wang Chuan;Zhang Haoyu;Chen Lijia;Zhou Ge;Cheng Jun;Zhang Siqian(Shenyang University of Technology,Shenyang 110870,China;Liaoning University,Shenyang 110036,China;Northwest Institute for Nonferrous Metal Research,Xi’an 710016,China)

机构地区：[1]沈阳工业大学,辽宁沈阳110870 [2]辽宁大学,辽宁沈阳110036 [3]西北有色金属研究院,陕西西安710016

出　　处：《稀有金属材料与工程》2024年第8期2241-2249,共9页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(U21A20117,52104379,52071219)。

摘　　要：海洋工程用近β钛合金在海水中易发生应力腐蚀开裂,合金相组成对其应力腐蚀行为具有显著影响。本实验通过对近β合金Ti-3Al-5Mo-4Nb-4Cr-2Zr进行3种不同工艺的热处理,使合金具有不同的3种相组成,利用扫描电子显微镜和X射线衍射仪分析显微组织,并进行电化学实验与慢应变速率拉伸实验,研究相组成不同时合金的应力腐蚀行为。结果表明,在β相区固溶处理后,合金为全β相组织(Pβ);500℃/6 h时效处理后,于β基体析出细小且间距较小次生α(αs)相(Pβ+fα);650℃/6 h时效处理后,于β基体析出了粗大且间距较大αs相(Pβ+cα)。Pβ+cα的自腐蚀电位相对最小、腐蚀电流密度相对最大、容抗弧仰角及0.01 Hz下阻抗模量相对最小,其耐腐蚀性相对最差,相对更优的依次为Pβ+fα和Pβ。应力腐蚀敏感性指数由高到低依次为Pβ+cα、Pβ+fα、Pβ。应力腐蚀断口表面出现韧窝、微裂纹、撕裂棱以及小平面,表明发生了高度位错运动和局部塑性变形。应力腐蚀开裂主要由氢吸附诱导位错发射(AIDE)和氢加速局部塑性变形(HELP)机制主导。αs相间距减小有利于降低合金应力腐蚀开裂倾向。Near-βtitanium alloys for marine engineering may be suffered from stress corrosion cracking.The phase composition has a significant impact on stress corrosion behavior.Different phase composition of a near-βtitanium alloy,Ti-3Al-5Mo-4Nb-4Cr-2Zr,was obtained by various heat treatments.The microstructures were characterized by scanning electron microscope and X-ray diffractometer.The electrochemical measurements and slow strain rate testing were carried out to investigate the effect of phase composition on stress corrosion behavior.The results indicate that the singleβphase is obtained by solution treatment atβphase field(Pβ).After ageing at 500℃for 6 h,fine secondaryαphase with narrow spacing precipitates withinβmatrix(Pβ+fα).After aging at 650℃for 6 h,coarsened secondaryαphase with wide spacing precipitates withinβmatrix(Pβ+cα).For the Pβ+cα,the corrosion potential and elevation angle of capacitive impedance arc as well as impedance modulus at 0.01 Hz are relatively minimum,and the corrosion current density is relatively maximum.The Pβ+cαexhibits relatively poor corrosion resistance.The relatively better order is the Pβ+fαand Pβ.The stress corrosion susceptibility index order from high to low is Pβ+cα,Pβ+fα,Pβ.The fracture morphology exhibits a mixed characteristic with shallow dimples and micro-cracks as well as tear ridges and flat facets.The combination of absorption induced dislocation emission(AIDE)and hydrogen enhanced localized plasticity(HELP)is the main mechanism for stress corrosion cracking.The decrease in secondaryαphase spacing has a beneficial effect on reducing the stress corrosion susceptibility.

关 键 词：近Β钛合金 次生α相 应力腐蚀行为 

分 类 号：TG146.23[一般工业技术—材料科学与工程]