【摘要】：激光噴丸技術(shù)通過激光誘導(dǎo)等離子體產(chǎn)生高幅沖擊波壓力,向材料表層植入高幅殘余壓應(yīng)力,同時(shí)增加表層位錯(cuò)密度、細(xì)化晶粒以提高材料的機(jī)械力學(xué)性能。針對強(qiáng)化性能在高溫和循環(huán)載荷條件下的穩(wěn)定性問題,溫度輔助的激光噴丸強(qiáng)化技術(shù)已日益受到國內(nèi)外學(xué)者的關(guān)注。本文以典型航空鋁合金2024-T351為研究對象,探索深冷預(yù)處理對2024-T531鋁合金組織性能及激光噴丸強(qiáng)化效果的影響,主要工作包括:(1)理論上探索了深冷預(yù)處理對激光噴丸2024-T351鋁合金殘余應(yīng)力及疲勞性能的影響,分析了激光噴丸誘導(dǎo)殘余應(yīng)力場、殘余應(yīng)力對金屬疲勞性能的影響及高溫、振動(dòng)和交變載荷條件下殘余應(yīng)力穩(wěn)定性等關(guān)鍵問題,研究了深冷預(yù)處理對2024-T351鋁合金材料屈服強(qiáng)度、硬度以及彈性模量等力學(xué)性能影響的相關(guān)理論,為深冷預(yù)處理和激光噴丸改性工藝研究提供理論基礎(chǔ)。(2)實(shí)驗(yàn)研究了深冷預(yù)處理對2024-T351鋁合金微觀組織、靜態(tài)力學(xué)性能及表面殘余應(yīng)力的影響。以液氮(-196℃)為介質(zhì)對鋁合金材料進(jìn)行2h~12h等不同時(shí)長的深冷預(yù)處理,隨后進(jìn)行常溫拉伸和納米壓痕等性能測試;對深冷前后材料金相組織、第二相狀態(tài)和表面殘余應(yīng)力進(jìn)行檢測分析。結(jié)果表明,深冷預(yù)處理后材料的微觀組織得到改善,其抗拉極限、屈服強(qiáng)度、納米硬度及彈性模量等明顯提高,拉伸斷口形貌的局部解理特征向塑性斷裂特征轉(zhuǎn)化,說明深冷預(yù)處理亦可提高2024-T351鋁合金塑性。殘余應(yīng)力測試表明深冷預(yù)處理可消除2024-T351鋁合金表面殘余拉應(yīng)力,并引入小幅殘余壓應(yīng)力。(3)開展了激光噴丸處理2024-T351鋁合金系列實(shí)驗(yàn)及其相關(guān)性能測試,研究了經(jīng)深冷預(yù)處理和未處理材料的激光噴丸強(qiáng)化效果。結(jié)果表明深冷預(yù)處理后進(jìn)行激光噴丸處理,材料的晶粒更加圓整且晶界更為清晰,表面殘余應(yīng)力幅值和激光噴丸影響層硬度明顯增加;“梯度交變載荷”作用下的殘余應(yīng)力穩(wěn)定性和疲勞性能測試分析表明,深冷預(yù)處理和激光噴丸均能提升2024-T351鋁合金的疲勞壽命,同時(shí)深冷預(yù)處理能顯著提高激光噴丸2024-T351鋁合金殘余應(yīng)力場的穩(wěn)定性,因而深冷后進(jìn)行激光噴丸處理的材料疲勞增益更明顯。
[Abstract]:Laser shot peening technique produces high amplitude shock wave pressure by laser-induced plasma, implants high amplitude residual compressive stress into the surface layer of the material, increases the dislocation density of the surface layer, and refines the grain size to improve the mechanical and mechanical properties of the material. Aiming at the stability of strengthening performance under high temperature and cyclic load, the temperature-assisted laser shot peening technique has been paid more and more attention by scholars at home and abroad. In this paper, the effect of cryogenic pretreatment on the microstructure and properties of 2024-T531 aluminum alloy and the effect of laser shot peening on the microstructure of typical aviation aluminum alloy 2024-T351 were studied. The main works are as follows: (1) the effects of cryogenic pretreatment on residual stress and fatigue properties of laser shot peening 2024-T351 aluminum alloy are studied theoretically. The residual stress field induced by laser shot peening, the effect of residual stress on metal fatigue performance and high temperature are analyzed. The influence of cryogenic pretreatment on the yield strength, hardness and elastic modulus of 2024-T351 aluminum alloy was studied. It provides a theoretical basis for the study of cryogenic pretreatment and laser shot peening. (2) the effects of cryogenic pretreatment on microstructure, static mechanical properties and surface residual stress of 2024-T351 aluminum alloy were studied experimentally. Aluminum alloy materials were pretreated with liquid nitrogen (-196 鈩，

本文編號：2293247