本文選題：高熵合金 + 預(yù)形變　； 參考：《濟(jì)南大學(xué)》2017年碩士論文

【摘要】：高熵合金打破了傳統(tǒng)合金配比理念,通常采取等原子比或近等原子比方式制備新型合金,因其全新的設(shè)計(jì)理念、獨(dú)特的結(jié)構(gòu)和優(yōu)異的力學(xué)性能、良好的耐蝕性、耐磨性及電磁學(xué)性能,引起了廣泛的研究興趣,具有廣闊的前景。本課題采用電弧熔煉法制備CoCrFeNi、CoCrFeNiWx和CoCrFeNi Mox(x=0.2,0.5)高熵合金,利用X射線衍射儀,差示掃描量熱儀,場(chǎng)發(fā)射掃描電鏡,電化學(xué)工作站、顯微硬度計(jì)和MTS萬能試驗(yàn)機(jī)等分析和測(cè)試手段研究預(yù)形變處理及元素添加對(duì)含CoCrFeNi高熵合金微觀結(jié)構(gòu)、形貌、成分、海水耐蝕性及力學(xué)性能的影響。以期通過新工藝設(shè)計(jì)及新成分的引入兩種方法,獲得力學(xué)性能和海水耐蝕性優(yōu)異的高熵合金。主要研究結(jié)果如下:1.鑄態(tài)CoCrFeNi高熵合金具有單一的FCC固溶體結(jié)構(gòu),微區(qū)形貌為典型的樹枝晶結(jié)構(gòu)。在力學(xué)性能方面,鑄態(tài)CoCrFeNi高熵合金表現(xiàn)出優(yōu)異的塑性變形能力;但屈服強(qiáng)度和顯微硬度較低,分別為167 MPa和168.9 HV。對(duì)CoCrFeNi高熵合金進(jìn)行不同形變量的預(yù)壓處理發(fā)現(xiàn),預(yù)壓形變量為20%和50%的高熵合金依然保持著單一的FCC固溶體結(jié)構(gòu);而進(jìn)行80%預(yù)壓處理的合金其相結(jié)構(gòu)發(fā)生了明顯的改變,由單一的FCC固溶體轉(zhuǎn)變?yōu)镕eNi3型的金屬間化合物相(FCC結(jié)構(gòu))。適當(dāng)預(yù)壓處理可以改善CoCrFeNi高熵合金的電化學(xué)海水耐蝕性,其中進(jìn)行80%預(yù)壓處理的合金點(diǎn)蝕電位右移,達(dá)到0.978 V,明顯高于鑄態(tài)CoCrFeNi高熵合金的0.157 V,并且出現(xiàn)了典型的二次鈍化現(xiàn)象,顯示出優(yōu)異的耐點(diǎn)蝕性。此外,適當(dāng)?shù)念A(yù)壓處理可以提高鑄態(tài)CoCrFeNi高熵合金的力學(xué)性能,進(jìn)行20%和50%預(yù)壓處理的合金屈服強(qiáng)度分別達(dá)到544 MPa和784 MPa,明顯高于鑄態(tài)CoCrFeNi高熵合金的163 MPa,分別提升233%和380%。2.W0.2和Mo0.2添加使CoCrFeNiW0.2/Mo0.2高熵合金仍保持單一的FCC固溶體結(jié)構(gòu),少量的W和Mo可以完全固溶到合金晶格中,未能引起相結(jié)構(gòu)變化;隨著W和Mo含量的進(jìn)一步提升,CoCrFeNi W0.5/Mo0.5高熵合金均在原有FCC固溶體結(jié)構(gòu)的基礎(chǔ)上分別析出了富W和富Mo的金屬間化合物相,新析出的金屬間化合物相沿枝晶間分布。W和Mo元素的添加均能提高鑄態(tài)CoCrFeNi高熵合金的電化學(xué)海水耐蝕性,其中CoCrFeNi W0.5/Mo0.2高熵合金出現(xiàn)了明顯的二次鈍化現(xiàn)象。此外,CoCrFeNiW0.5高熵合金顯示出最為優(yōu)異的耐點(diǎn)蝕性,其點(diǎn)蝕電位達(dá)到1.112 V,明顯高于鑄態(tài)CoCrFeNi的0.157 V;其鈍化區(qū)間由1.155 V提升到2.291 V,提升為原來的將近2倍,鈍化膜穩(wěn)定性得到較大的提升。W和Mo元素的添加均能顯著提高鑄態(tài)CoCrFeNi高熵合金的顯微硬度及屈服強(qiáng)度,W0.2和Mo0.2合金力學(xué)性能的增強(qiáng)與固溶強(qiáng)化有關(guān),W0.5和Mo0.5合金的強(qiáng)化機(jī)制為固溶強(qiáng)化和第二相增強(qiáng)理論。其中,Mo0.5添加的高熵合金顯微硬度達(dá)到356HV,屈服強(qiáng)度和極限抗壓強(qiáng)度分別為604 MPa和1724 MPa,極限應(yīng)變量達(dá)到49.1%,表現(xiàn)出優(yōu)異的綜合力學(xué)性能。
[Abstract]:High entropy alloy has broken the traditional concept of alloying ratio. It is usually prepared by equal or near equal atomic ratio. Because of its new design idea, unique structure, excellent mechanical properties, good corrosion resistance, high entropy alloy is a new type of alloy, because of its new design concept, unique structure, excellent mechanical properties, good corrosion resistance, and good corrosion resistance. Wear resistance and electromagnetic properties have attracted extensive research interest and have broad prospects. In this paper, CoCrFeNiNix CoCrFeNiWx and CoCrFeNi Moxtrox0. 2) high entropy alloys were prepared by arc melting. X-ray diffractometer, differential scanning calorimeter, field emission scanning electron microscope and electrochemical workstation were used. The effects of predeformation treatment and element addition on the microstructure, morphology, composition, corrosion resistance and mechanical properties of high entropy alloy containing CoCrFeNi were studied by means of microhardness tester and MTS universal tester. The high entropy alloy with excellent mechanical properties and corrosion resistance of seawater can be obtained by the new process design and the introduction of new composition. The main results are as follows: 1. The as-cast CoCrFeNi high entropy alloy has a single FCC solid solution structure and a typical dendritic structure. In terms of mechanical properties, as cast CoCrFeNi high entropy alloy shows excellent plastic deformation ability, but its yield strength and microhardness are lower, which are 167 MPa and 168.9 HV, respectively. By prepressing CoCrFeNi high entropy alloy with different shape variables, it was found that the high entropy alloy with 20% and 50% precompression deformation still maintained a single FCC solid solution structure, while the phase structure of 80% prepress alloy changed obviously. The FCC structure was transformed from a single FCC solid solution to a FeNi3 type intermetallic compound. The electrochemical corrosion resistance of CoCrFeNi high entropy alloy can be improved by proper preloading, in which the pitting potential of 80% prepress alloy shifts to the right, reaching 0.978 V, which is obviously higher than that of as cast CoCrFeNi high entropy alloy (0.157 V), and the typical secondary passivation occurs. Show excellent pitting resistance. In addition, the mechanical properties of as-cast CoCrFeNi high entropy alloy can be improved by proper preloading treatment. The yield strength of the alloy treated with 20% and 50% precompression was 544 MPa and 784 MPA, respectively, which was significantly higher than that of the as-cast CoCrFeNi high entropy alloy (163 MPA). The CoCrFeNiW0.2/Mo0.2 high entropy alloy remained a single FCC solid solution structure by 233% increase and 380%.2.W0.2 and Mo0.2 addition, respectively. A small amount of W and Mo can be completely dissolved into the lattice of the alloy, and the phase structure can not be changed. With the further increase of W and Mo contents, W and Mo rich intermetallic compound phases were precipitated on the basis of the original FCC solid solution structure of CoCrFeNi W0.5/Mo0.5 high entropy alloys, respectively. The electrochemical corrosion resistance of as-cast CoCrFeNi high entropy alloy can be improved by the addition of new precipitated intermetallics. W and Mo elements along the dendritic phase. Among them, the CoCrFeNi W0.5/Mo0.2 high entropy alloy has obvious secondary passivation phenomenon. In addition, CoCrFeNiW0.5 high entropy alloy shows the most excellent pitting corrosion resistance, its pitting potential is 1.112 V, which is obviously higher than 0.157 V of as-cast CoCrFeNi, and its passivation range is raised from 1.155 V to 2.291 V, which is nearly twice as high as the original one. The stability of passivation film is improved greatly. W and Mo elements can improve the microhardness and yield strength of as cast CoCrFeNi high entropy alloy. The mechanical properties of W 0.2 and Mo0.2 alloys are related to solution strengthening. The strength of W 0.5 and Mo0.5 alloys is related to solution strengthening. The mechanism is solid solution strengthening and second phase enhancement theory. The microhardness, yield strength and ultimate compressive strength of the high entropy alloy added with Mo0.5,604 MPa and 1724 MPA, respectively, and the ultimate strain reached 49.1%, showing excellent comprehensive mechanical properties.
【學(xué)位授予單位】：濟(jì)南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG139

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