發(fā)布時(shí)間：2018-06-08 17:29

  本文選題：熱力學(xué) + 高熵合金�。� 參考：《沈陽航空航天大學(xué)》2015年碩士論文

【摘要】：高熵合金是近些年來受到研究領(lǐng)域關(guān)注的一類新型合金�，F(xiàn)有的高熵合金主要是選擇密度較大的Co，Cr，F(xiàn)e，Ni，Mn等過渡族金屬元素作為主元素。本文選擇Al，Mg，Ti，Ca，Li等密度較小的金屬元素作為主元素，嘗試制備高比強(qiáng)度的輕質(zhì)高熵合金。 本文根據(jù)已有的高熵合金固溶體形成理論設(shè)計(jì)了8組合金的配方，采用真空感應(yīng)爐熔煉，并用直徑為20mm的鋼模和直徑為5mm的銅模分別鑄造兩種冷卻速度不同的試樣用以對比。通過XRD，SEM和EDS對合金的相組成與組織結(jié)構(gòu)進(jìn)行了分析，并利用萬能試驗(yàn)機(jī)對合金的力學(xué)性能進(jìn)行測試，利用阿基米德法測定合金的密度，計(jì)算其比強(qiáng)度，對合金的成分進(jìn)行化學(xué)成分分析以驗(yàn)證成分設(shè)計(jì)理論的準(zhǔn)確性。 研究結(jié)果表明，Al-Mg-Zn-Sn-Cu系合金中Mg元素與Sn元素首先結(jié)合生成Mg2Sn相，多余的Sn元素在晶間富集。Al，Cu，Zn三種元素在原子含量相差不大時(shí)，會生成Al4.2Cu3.2Zn0.7相，但當(dāng)相差太多時(shí)，會生成更穩(wěn)定的金屬間化合物，如CuAl2等。高熵效應(yīng)使合金獲得了較好的力學(xué)性能。其中，Al7MgSnCu4.6Zn6.4合金的強(qiáng)度與硬度均較高，它比強(qiáng)度達(dá)到2.245×105(N/m2)/(kg/m3)，而冷卻速度較快的試樣的硬度為270.75HV。 對于Al-Mg-Zn-Sn-Cu-Ti系合金， Mg和Ti不共存于同一相中。其中，Al7Mg3.6Cu1.2Zn7Ti1.2合金由一種HCP相和兩種FCC相組成。它的比強(qiáng)度很高，達(dá)到1.491×105(N/m2)/(kg/m3)，而密度僅為3.84g/cm3。合金的硬度也很高，在冷卻速度較慢的試樣中，達(dá)到434.3HV。 對于Al-Mg-Ca-Li-M系合金，由于其主要成分都是一些輕質(zhì)金屬，所以合金的密度較低。AlMgCa0.5LiCu合金的密度為2.63g/cm3，而AlMgCa0.5LiZn合金的密度為2.65g/cm3，它們都接近于Al合金的密度。其中，，AlMgCa0.5LiCu合金具有較高的比強(qiáng)度，為1.15×105(N/m2)/(kg/m3)。 通過上述結(jié)果的分析認(rèn)為，設(shè)計(jì)高熵合金的成分時(shí)，不僅要考慮合金總體的混合焓值，還要考慮到合金中各組分之間的混合焓值以及各元素的原子半徑大小，這樣可以避免過多的金屬間化合物生成或者大量的成分偏析。
[Abstract]:High entropy alloy is a new kind of alloy which has attracted much attention in recent years. The existing high-entropy alloys are mainly composed of transition metal elements such as Co-Cr-Fe, Ni, mn and so on, which are selected as the main elements. In this paper, the light weight and high entropy alloy with high specific strength is prepared by selecting the metal elements with low density, such as Al _ 2O _ 3, mg, Ti, Ca, Li, as main elements. According to the theory of solid solution formation of high-entropy alloy, the formula of eight combinations of gold is designed and melted by vacuum induction furnace. The steel die with diameter 20mm and copper die with diameter of 5mm were cast two kinds of specimens with different cooling rate respectively. The phase composition and microstructure of the alloy were analyzed by XRDX SEM and EDS. The mechanical properties of the alloy were tested by universal testing machine. The density of the alloy was measured by Archimedes method and the specific strength was calculated. The chemical composition analysis of the alloy was carried out to verify the accuracy of the composition design theory. The results showed that the mg element and Sn element in the Al-Mg-Zn-Sn-Cu system alloy first combined to form Mg2Sn phase. The superfluous Sn element in the intergranular enrichment. The three elements, Al4.2Cu3.2Zn0.7 phase, will form when the atomic content is not different, but when the difference is too much, it will produce more stable intermetallic compounds, such as CuAl2 and so on. The high entropy effect makes the alloy obtain better mechanical properties. The strength and hardness of Al-7MgSnCu4.6Zn6.4 alloy are both high, and its specific strength is 2.245 脳 10 ~ 5 N / m ~ (2 / m ~ (-2) / kg 路m ~ (3), while the hardness of the sample with faster cooling rate is 270.75 HV. For Al-Mg-Zn-Sn-Cu-Ti alloy, mg and Ti do not coexist in the same phase. The Al _ 7mg _ (3.6) Cu _ (1.2) Zn _ (7) Ti _ (1.2) alloy consists of one HCP phase and two FCC phases. Its specific strength is very high, reaching 1.491 脳 10 ~ 5 N / m ~ (2) / m ~ (2) 路kg ~ (-3) 路m ~ (3), but the density is only 3.84 g / cm ~ (3). The hardness of Al-Mg-Ca-Li-M alloy is also very high, and the hardness of Al-Mg-Ca-Li-M alloy is 434.3 HV in the sample with slow cooling rate. For Al-Mg-Ca-Li-M alloy, the main composition is some light metal, So the density of AlMgCa0.5LiCu alloy is 2.63g / cm ~ 3, and that of AlMgCa0.5LiZn alloy is 2.65g / cm ~ 3, which is close to that of Al alloy. AlMgCa0.5LiCu alloy has a high specific strength of 1.15 脳 10 ~ (5) N / m ~ (2) / m ~ (2) 路kg ~ (-3) 路m ~ (3). Through the analysis of the above results, it is concluded that not only the total enthalpy value of the alloy should be taken into account in designing the composition of the high-entropy alloy, but also the total enthalpy of the alloy should be considered. The enthalpy of each component in the alloy and the atomic radius of each element can be taken into account in order to avoid the formation of too many intermetallic compounds or the segregation of a large number of components.
【學(xué)位授予單位】：沈陽航空航天大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG132

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