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

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

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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 ℃/6h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.
Stress Corrosion Behavior of Near-β Titanium Alloy Ti-3Al-5Mo-4Nb-4Cr-2Zr with Different Phase Composition
Near-β titanium 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-β titanium 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 single β phase is obtained by solution treatment at β phase field(Pβ).After ageing at 500 ℃ for 6 h,fine secondary α phase with narrow spacing precipitates within β matrix(Pβ+fα).After aging at 650 ℃ for 6 h,coarsened secondary α phase with wide spacing precipitates within β matrix(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+cα exhibits relatively poor corrosion resistance.The relatively better order is the Pβ+rα and 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 secondary α phase spacing has a beneficial effect on reducing the stress corrosion susceptibility.

near-β titanium alloysecondary α phasestress corrosion behavior

王川、张浩宇、陈立佳、周舸、程军、张思倩

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沈阳工业大学,辽宁沈阳 110870

辽宁大学,辽宁沈阳 110036

西北有色金属研究院,陕西西安 710016

近β钛合金 次生α相 应力腐蚀行为

国家自然科学基金国家自然科学基金国家自然科学基金

U21A201175210437952071219

2024

稀有金属材料与工程
中国有色金属学会,中国材料研究学会,西北有色金属研究院

稀有金属材料与工程

CSTPCD北大核心
影响因子:0.634
ISSN:1002-185X
年,卷(期):2024.53(8)