發(fā)布時間：2018-10-20 08:39

【摘要】：鈦合金具有低密度、高比強度、優(yōu)良的高溫低溫性能及抗磨損等性能而廣泛應用于航空航天、艦船制造、海洋工程、化工、冶金及國防工業(yè)領域。TC4(Ti-6Al-4V)是世界上開發(fā)最早、應用最廣的鈦合金。它的產(chǎn)量約占全世界各種鈦合金半成品總產(chǎn)量的一半以上,在航空航天工業(yè)中超過80%。TC4鈦合金的主要特點是優(yōu)異的綜合性能和良好的工藝特性。還具有優(yōu)良的超塑性,適合于用各種壓力加工方法進行成形,并采用各種方式進行焊接。該合金主要在退火狀態(tài)下使用,也可采用固溶時效強化,然而淬透面不超過25～30mm,固溶時效強化不適合厚大工件。Al、V合金元素成本較高,同時也限制了其更為廣泛的應用。目前,針對不同的使用條件和工藝要求,各國都出現(xiàn)了許多TC4鈦合金的改型。Ti-Al-V-Fe-O系合金是美國ATI公司研發(fā)的一種取代傳統(tǒng)TC4的新型雙相鈦合金,不僅具有較高的強度,同時耐磨耐蝕性能、延展性能等綜合性能優(yōu)異而且成本低廉,因此在航空航天、軍工等高科技領域得到了廣泛的應用。該合金中添加廉價Fe元素替代部分V作為β穩(wěn)定元素,添加O替代部分Al作為α穩(wěn)定元素,降低了合金的成本;Fe和O的加入降低了 ω相的熱力學穩(wěn)定性,從而獲得更多的β相,提高了合金的塑性和強度。目前,國外主要將Ti-Al-V-Fe-O系鈦合金用于軍事和航天工業(yè)研發(fā),除對外公布合金的退火組織呈等軸組織外,其它強化熱處理工藝、合金元素對力學性能的強化機理及組織演變規(guī)律則并未公開。該實驗中利用真空感應熔煉技術(ISM)進行熔煉,并軋制得到5mm厚的熱軋板,對其進行固溶時效處理。研究了固溶溫度和時效溫度對其微觀結構、組織形貌、力學性能和耐磨性能的影響,并且對其變化機制進行了相應的分析。得出了以下結論:該種鈦合金處理前后均由α和β兩相組成,在固溶處理過程中,出現(xiàn)了α相向β轉變組織的轉變,微觀形貌由等軸組織向全片層組織轉變,經(jīng)過時效處理,β轉變組織分解生成次生α相,片層組織消失,微觀形貌由混亂雙態(tài)組織向等軸組織轉變;試樣在固溶處理后,910℃的高溫退火作用,與熱軋態(tài)相比,強度降低,斷后延伸率有所提高,當溫度達到940℃時,強度升高,延伸率下降。當固溶溫度超過相變點以后,試樣中出現(xiàn)了“β脆”現(xiàn)象,性能急劇下降,強度和延伸率同時下降。時效處理后,強度和塑性均得到了提高。隨著時效溫度的升高,次生α相逐漸長大,強度逐漸降低,而延伸率逐漸升高。940℃×15min/AC+500℃×6h/AC熱處理后的板材強度和延伸率分別達到1260MPa、8.5%,具有較佳的綜合性能。與熱軋態(tài)相比,固溶時效強化以后硬度與耐磨性能都得到了提高。隨著時效溫度的升高,試樣硬度下降,耐磨性降低。
[Abstract]:Titanium alloys are widely used in aerospace, shipbuilding, marine engineering, chemical, metallurgical and national defense industries due to their low density, high specific strength, excellent high temperature and low temperature properties and wear resistance. TC4 (Ti-6Al-4V) is the first developed in the world. The most widely used titanium alloy. Its output accounts for more than half of the total output of all kinds of titanium alloy semi-finished products in the world. The main characteristic of 80%.TC4 titanium alloy in aerospace industry is its excellent comprehensive properties and good technological characteristics. It also has excellent superplasticity, which is suitable for forming by various pressure processing methods and welding by various methods. The alloy is mainly used in annealing and can also be strengthened by solid solution aging. However, the quenching surface is not more than 250mm and the solution aging strengthening is not suitable for the thick workpiece. The cost of Al,V alloy elements is higher, and its wider application is limited. At present, according to different application conditions and process requirements, many modification of TC4 titanium alloys have appeared in many countries. Ti-Al-V-Fe-O series alloys are a new type of dual-phase titanium alloys developed by ATI Company of USA, which not only have high strength, but also replace traditional TC4. At the same time, wear and corrosion resistance, extensibility and other comprehensive properties are excellent and low cost, so it has been widely used in aerospace, military industry and other high-tech fields. The cost of the alloy is reduced by adding cheap Fe element to replace part V as 尾 stable element and adding O to replace part of Al as 偽 stable element, and the addition of Fe and O reduces the thermodynamic stability of 蠅 phase. As a result, more 尾-phases were obtained, and the plasticity and strength of the alloy were improved. At present, Ti-Al-V-Fe-O series titanium alloys are mainly used in military and aerospace industry research and development abroad. In addition to announcing the annealing structure of the alloy as equiaxed structure, other strengthening heat treatment processes are also used. The mechanism of strengthening mechanical properties and the law of microstructure evolution of alloy elements have not been disclosed. In this experiment, the vacuum induction melting technology (ISM) was used to melt the hot rolled plate with 5mm thickness and the solution aging treatment was carried out. The effects of solution temperature and aging temperature on microstructure, mechanical properties and wear resistance were studied. The conclusions are as follows: the titanium alloy is composed of 偽 and 尾 phases before and after treatment. During the process of solution treatment, the transformation of 偽 phase to 尾 phase occurs, and the microstructure of the alloy changes from equiaxed structure to whole lamellar structure. After aging treatment, the 尾 -transition microstructure decomposes to form a secondary phase, the lamellar structure disappears, the microstructure changes from disordered two-state structure to equiaxed structure, and the strength of the sample annealed at 910 鈩，

本文編號：2282629