(西南交通大學(xué) 材料先進(jìn)技術(shù)教育部重點實驗室，成都 610031)
摘 要: 通過噴丸和電解拋光的方法處理Ti-44Al-5Nb-1W-1B(摩爾分?jǐn)?shù)，%)合金，研究其在長期熱暴露(10000 h, 700 ℃)前后疲勞性能的變化。結(jié)果表明：在熱暴露前，電解拋光處理比噴丸處理更能改善該合金的疲勞性能。經(jīng)過長期熱暴露后，兩種表面處理樣品的疲勞性能均出現(xiàn)不同程度的衰減，但電解拋光處理相對于噴丸處理能夠更好地保持合金的疲勞性能。長期熱暴露會導(dǎo)致合金表面發(fā)生氧化，合金內(nèi)部發(fā)生“釋氧脆化”和“B2+ω有序相生成脆化”，這3種變化均對合金的疲勞性能產(chǎn)生不利影響。表面氧化使得噴丸工藝所引入的表層殘余壓應(yīng)力在長期熱暴露時明顯降低，這導(dǎo)致疲勞性能大幅度衰減。相對而言，電解拋光工藝使合金獲得光滑平整無缺陷的表面，無明顯應(yīng)力集中，因此合金有較高的抵抗熱暴露性能衰退的能力。
關(guān)鍵字: TiAl合金；長期熱暴露；噴丸；電解拋光；疲勞性能
（Key Laboratory of Advanced Technologies of Materials, Ministry of Education,
Southwest Jiaotong University, Chengdu 610031, China）
Abstract:The Ti-44Al-5Nb-1W-1B(mole fraction, %) alloy was treated by two surface treatment processes of shot peening and electropolishing, the changes of the fatigue behavior of the alloy exposed at 700 ℃ in air for 10000 h was studied. The results show that the fatigue strength of electropolishing specimens is higher than that of shot peening specimens before exposure. The fatigue strengths of the alloys with both surface conditions reduce after long-term thermal exposure, but the electropolishing specimens can maintain the fatigue properties of the alloy better than the shot-peening specimens. Long-term thermal exposure can cause oxidation on the surface and “B2+ω-formation induced embrittlement” and “oxygen-release induced embrittlement” inside of the alloy. All the three types of changes are detrimental to the fatigue performance of the alloy. The residual compressive stresses introduced by shot peening are released during long-term thermal exposure owing to the oxidation, which leads to a significant deterioration of the fatigue properties. The electropolishing specimens have very smooth surface without defects and stress concentration, therefore, the electropolishing specimens are more capable of resisting the deterioration of the fatigue properties than shot peening specimens during long-term thermal exposure.
Key words: TiAl alloy; long-term thermal exposure; shot peening; electropolishing; fatigue performance
