張志彬 周志丹
摘 要:為了解決鋁基非晶合金在形成過程中容易析出α-Al晶體導(dǎo)致玻璃形成能力較低且不易評估的問題,設(shè)計(jì)了簡單易行的玻璃形成能力評估方法,對非晶AlNiZr合金成分進(jìn)行優(yōu)化。首先,制備9種不同組分的AlNiZr合金鑄錠;然后,在相同制備條件下,用單輥甩帶法制備不同組分的合金薄帶;最后,采用X射線衍射儀對薄帶進(jìn)行XRD表征,基于XRD結(jié)果擬合計(jì)算合金薄帶的非晶含量。結(jié)果表明:在合金組分Al100-x-yNixZry中,隨著Ni含量的增加玻璃形成能力提高,隨著Zr含量的增加玻璃形能力成降低;當(dāng)Zr含量為3%時(shí),進(jìn)一步增加Ni含量達(dá)到20%和25%,合金的玻璃形成能力降低,Al82Ni15Zr3具有更好的玻璃形成能力。通過對非晶AlNiZr合金成分的優(yōu)化,可以為不含稀土元素的鋁基合金的玻璃形成能力評估提供新的方法,拓展其在設(shè)備防護(hù)領(lǐng)域的應(yīng)用空間。
關(guān)鍵詞:非晶、微晶金屬材料;鋁基合金;非晶合金;玻璃形成能力;組分優(yōu)化;非晶含量
中圖分類號:TG139+.8;TB31?? 文獻(xiàn)標(biāo)識碼:A
doi:10.7535/hbkd.2021yx04011
收稿日期:2021-05-24;修回日期:2021-06-19;責(zé)任編輯:張士瑩
基金項(xiàng)目:國家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2018YFC1902400)
第一作者簡介:張志彬(1982—),男,河北邢臺人,高級工程師,博士,主要從事鋁基非晶材料及應(yīng)用基礎(chǔ)研究工作。
E-mail:eacbia@163.com
張志彬,周志丹.非晶AlNiZr合金成分的優(yōu)化[J].河北科技大學(xué)學(xué)報(bào),2021,42(4):410-414.ZHANG Zhibin,ZHOU Zhidan.Composition optimization of amorphous AlNiZr alloys[J].Journal of Hebei University of Science and Technology,2021,42(4):410-414.
Composition optimization of amorphous AlNiZr alloys
ZHANG Zhibin,ZHOU Zhidan
(National Innovation Institute of Defense Technology,Academy of Military Sciences of PLA,Beijing 100071,China)
Abstract:In order to solve the problem that the glass forming ability of Al-based amorphous alloy is not easy to be evaluated because of the easy precipitation of α-Al crystal in the glass forming process,a simple and feasible glass forming ability evaluation scheme was designedto optimize the composition of amorphous AlNiZr alloy.Firstly,nine kinds of AlNiZr alloy ingots with different compositions were prepared; Then,under the same preparation conditions,the alloy ribbons with different compositions were prepared by single-roll strip casting method; Finally,the ribbons were characterized by XRD,and the amorphous content of alloy ribbon was calculated based on the XRD results.The results show that the glass-forming ability of Al100-x-yNixZryincreases with the increase of Ni content and decreases with the increase of Zr content; When the Zr content is 3% and the Ni content is further increased to 20% and 25%,the glass-forming ability of the alloy is reduced,and Al82Ni15Zr3 alloy has better glass-forming ability.By optimizing the compositions of amorphous AlNiZr alloy,a new evaluation scheme of glass-forming ability can be provided for the Al-based alloy without rare earth elements,and its application space in the field of equipment protection can be expanded.
Keywords:
amorphous and microcrystalline metal materials;Al-based alloy;amorphous alloy;glass-forming ability;component optimization;amorphous content
與傳統(tǒng)合金相比,非晶合金沒有晶界,不存在孿晶和位錯等缺陷,因此具有較好的強(qiáng)度和耐腐蝕性能[1-4]。近30年來,非晶合金的應(yīng)用得到了飛速發(fā)展[5-9]。在工業(yè)化應(yīng)用領(lǐng)域推廣較好的是鐵基非晶合金[10],這主要得益于其高飽和磁感應(yīng)強(qiáng)度、高磁導(dǎo)率、高玻璃形成能力,以及制備成本低等優(yōu)勢。鋁基非晶合金具有較高的強(qiáng)度質(zhì)量比,在航空航天領(lǐng)域應(yīng)用前景廣闊[11-12]。然而,鋁基非晶合金的玻璃形成能力較差,非晶態(tài)制備困難,嚴(yán)重制約了其發(fā)展進(jìn)程。
早在1965年,PREDECKI等[13]首次制備了非晶態(tài)的Al-Si合金,隨后又開發(fā)了一系列的二元鋁基非晶合金,如Al-Ge,Al-Cr和Al-Cu[14]等。然而受當(dāng)時(shí)技術(shù)制約,非晶合金中會含有部分晶體相。1981年,INOUE等[15]和SUZUKI等[16]在二元鋁基非晶基礎(chǔ)上,添加元素制備了完全非晶的Al-(Fe,Co)-B和Al-Fe-(Si,Ge)三元鋁基非晶合金,但這2種合金具有較大脆性,當(dāng)時(shí)并未引起人們的足夠重視。直至1987年,研究人員才制備出具有高韌性的Al-Ni-Si非晶合金[17]。隨后,鋁基非晶合金引起了國際社會的廣泛關(guān)注,各國學(xué)者陸續(xù)制備了拉伸強(qiáng)度高達(dá)1 000 MPa、具有較高比強(qiáng)度和韌性的鋁基非晶合金[18-23]。由于制備過程中鋁基非晶合金容易析出α-Al晶體,因而大大降低了其玻璃形成能力[24-26]。為了提高鋁基合金的玻璃形成能力,科研人員進(jìn)行了大量工作,如在二元鋁基合金中摻入稀土元素等[27-29]。隨著深入研究不同元素對鋁基合金玻璃形成能力的影響,鋁基合金組分也從三元擴(kuò)展到了五元。目前所報(bào)道的玻璃形成能力最高的鋁基合金組分是Al-Ni-Y-Co-La五元合金,其全非晶棒材的直徑可達(dá)2.5 mm[30]。含有稀土的多元鋁基合金能夠提高玻璃形成能力,但是其組分復(fù)雜,且含量不易控制。近年來,隨著稀土元素在電池、半導(dǎo)體和軍工領(lǐng)域的廣泛應(yīng)用,提升了含有稀土元素鋁基非晶合金的制備成本。有研究表明:鋁基非晶合金中,含有部分納米晶能夠在保持合金韌性的同時(shí),增加合金的硬度[15,31];通過熱噴涂技術(shù),可以較容易制備含有納米晶的鋁基非晶涂層[32-36]。對于金屬涂層形態(tài)而言,其厚度往往只有幾百微米,突破了塊體非晶合金中尺寸的限制,弱化了對合金玻璃形成能力的要求。不少學(xué)者在探究鋁基非晶合金在表面防護(hù)領(lǐng)域的應(yīng)用中,選擇了不含稀土元素的三元組分[26,32,34]。然而,不含稀土元素鋁基合金的玻璃形成能力差,很難用常規(guī)方法測量其玻璃轉(zhuǎn)變溫度(Tg),三元鋁基合金中各元素對合金玻璃形成能力影響的相關(guān)研究也較少。
筆者以Al-Ni-Zr合金為研究體系,設(shè)計(jì)不同的合金組分,通過單輥法制備合金薄帶,根據(jù)薄帶的非晶含量評估不同組分合金的玻璃形成能力,分析Ni元素和Zr元素對Al-Ni-Zr合金的影響。
1 實(shí)驗(yàn)部分
1.1 主要材料與設(shè)備
單質(zhì)Al,Ni和Zr,純度≥99.95%(質(zhì)量分?jǐn)?shù),下同),北京普瑞新材科技有限公司提供。
旋轉(zhuǎn)式真空銅模熔鑄系統(tǒng),型號NMS-DRⅡ,成都中科新材料科技有限公司提供;真空熔體超速急冷系統(tǒng),型號為NMS-GPⅡ,成都中科新材料科技有限公司提供;X射線衍射儀,D8型號,德國布魯克AXS公司提供;機(jī)械泵;分子泵。
1.2 制備合金鑄錠
采用單質(zhì)Al,Ni和Zr,通過真空電弧熔煉制備Al100-x-yNixZry(x=5,10和15,y=3,6和9;x=20和25,y=3;若不特別說明,分子式下標(biāo)均指代原子數(shù))組分的合金錠。熔煉設(shè)備采用旋轉(zhuǎn)式真空銅模熔鑄系統(tǒng),熔煉前打開循環(huán)水冷系統(tǒng)維持腔體溫度為15~20 ℃,清理銅坩堝、爐內(nèi)壁和鎢極雜質(zhì),將單質(zhì)去皮后按照設(shè)計(jì)組分配比置于坩堝中,其中將低密度的Al單質(zhì)放置在底層。關(guān)閉爐門,先后用機(jī)械泵和分子泵抽真空,爐內(nèi)真空度低于3×10-3 Pa時(shí)再充入氬氣,重復(fù)抽真空步驟以確保爐內(nèi)無氧氣及其他雜質(zhì)。開始熔煉后,先小電流引弧,隨后增大電流熔化金屬單質(zhì),于熔融狀態(tài)下開啟磁力攪拌,迅速實(shí)現(xiàn)合金化。熔液凝固后通過翻面進(jìn)行重熔,再次合金化。反復(fù)5次合金化過程,制得均勻的母合金錠。
1.3 制備合金薄帶
采用真空熔體超速急冷系統(tǒng),通過單輥甩帶法制備鋁基合金薄帶。清理爐腔并拋光銅輥,直至表面光滑如鏡面,隨后將去除表面氧化皮的合金錠破碎后進(jìn)行清洗。稱取約3 g,置于底部孔徑為0.9 mm的石英管中,將石英管置于銅線圈中,距離銅輥0.02 mm,關(guān)閉爐門。預(yù)熱擴(kuò)散泵,依次進(jìn)行抽低真空和高真空操作,使?fàn)t內(nèi)真空度達(dá)到5×10-3 Pa,隨后充入氬氣,重復(fù)抽真空操作確保爐腔內(nèi)無雜質(zhì)氣體。隨后緩慢充入氬氣,調(diào)整石英管內(nèi)、外壓差為0.02 Pa。進(jìn)入甩帶階段,打開電機(jī),將銅輥轉(zhuǎn)速調(diào)至38 m/s,打開整流器,調(diào)節(jié)電流為46 A,通過銅線圈加熱合金。待合金熔化后,打開電磁閥將熔融合金噴射到高速旋轉(zhuǎn)的銅輥表面,熔液快速凝固并被甩出形成合金薄帶。
1.4 樣品表征
用X射線衍射儀分析薄帶的相組成,儀器以CuKα為射線源,步長為0.02°,掃描速率為2°/min。依據(jù)基于薄帶的XRD衍射圖譜,擬合計(jì)算非晶含量[37],此方法在非晶涂層領(lǐng)域應(yīng)用廣泛[32,38-40]。
2 結(jié)果與討論
圖1所示為薄帶的XRD衍射圖。
圖1 a)為Ni固定為5%時(shí),不同Zr含量(3%,6%和9%)的鋁基合金薄帶的XRD衍射圖。從圖1 a)可以看出:各合金均由復(fù)雜晶體相組成,幾乎不含非晶相;當(dāng)Zr含量為9%時(shí),由于含量較高,存在明顯的Zr偏析,因此Al10Ni5Zr9合金中有Zr單質(zhì)相,此外合金中還有α-Al,Al3Ni,Al9.83Zr0.17和Al3Zr相;當(dāng)Zr含量降至6%時(shí),合金中的Zr單質(zhì)相消失,合金相的組成為α-Al和Al3Ni相;當(dāng)Zr含量為3%時(shí),晶體峰開始寬化,說明合金開始具有非晶化的傾向,主要相的組成為α-Al,Al3Ni和少量Al2NiZr6。圖1 b)為Ni含量為10%的合金薄帶的XRD衍射圖??梢钥闯觯篫r含量為9%時(shí),合金有明顯的α-Al相和少量Al3Ni相,另外在42°附近有一個較小的“饅頭峰”,該峰是非晶相的特征。對比Zr含量為6%和3%合金薄帶的XRD圖譜可知,隨著Zr含量的減少,晶體特征峰強(qiáng)度減弱,而非晶的“饅頭峰”更加凸顯。圖1 c)為Ni固定為15%時(shí)的合金薄帶的XRD衍射圖。當(dāng)Zr含量為9%時(shí),相較相同Zr含量而Ni為10%時(shí)的XRD衍射圖,合金的非晶特征更為明顯;當(dāng)Zr含量降至6%時(shí),合金XRD圖譜中的晶體特征峰基本消失,只有較明顯的非晶峰;Zr含量進(jìn)一步降低至3%時(shí),除了沒有晶體峰以外,其代表非晶相的“饅頭峰”顯得更加寬泛。
依據(jù)圖1中的XRD圖譜,通過擬合計(jì)算,可以得到不同組分的合金薄帶的非晶含量,如圖2所示。
相同條件下制備的鋁基合金薄帶,非晶含量越高則表示玻璃形成能力越強(qiáng)。在圖2所示的合金組分的范圍內(nèi),隨著Ni含量的增加,玻璃形成能力增大。隨著Zr含量的升高,玻璃形成能力降低。由此可知,Al82Ni15Zr3組分合金的玻璃形成能力較高。為進(jìn)一步優(yōu)化合金組分,可以增加Ni含量或者減少Zr含量。由于Zr含量已經(jīng)很少,進(jìn)一步優(yōu)化的空間很小,因此確定Zr的最佳含量為3%??梢酝ㄟ^進(jìn)一步增加Ni含量來比較其合金薄帶的非晶含量。
圖3所示為Zr含量為3%,Ni含量為15%,20%和25%時(shí)的合金薄帶的XRD衍射圖。
從圖3可以看出,當(dāng)Ni含量為20%時(shí),合金XRD圖中開始有出現(xiàn)晶體峰的傾向。當(dāng)Ni含量增至25%時(shí),從對應(yīng)的XRD衍射圖可以看出,合金已經(jīng)沒有非晶特征,合金存在Ni元素偏析且存在其他合金化合物,如Al3Ni和NiZr2等。當(dāng)Ni含量大于15%時(shí),合金的玻璃形成能力開始下降,由此可以確定具有最大玻璃形成能力的合金組分為Al82Ni15Zr3。
3 結(jié) 語
1)以Al-Ni-Zr為研究體系,針對AlNiZr合金玻璃形成能力不易評估的問題,設(shè)計(jì)了簡單的玻璃形成能力評估方法,對比了不同組分AlNiZr合金的玻璃形成能力。
2)通過對9組合金組分進(jìn)行研究,得出了Ni和Zr元素對合金的影響:隨著Ni含量的逐步增加,合金的玻璃形成能力越來越大;隨著Zr含量的增加,合金的玻璃形成能力越來越小。
3)固定Zr含量為3%,當(dāng)Ni含量超過15%后,合金的玻璃形成能力開始減小。通過優(yōu)化可知,具有最佳玻璃形成能力的合金組分為Al82Ni15Zr3。
4)本文為不含稀土元素的鋁基合金的玻璃形成能力評估提供了新方法,該方法也有望應(yīng)用于Zr基、Fe基等其他體系合金玻璃形成能力的評估中。在今后的工作中,可以基于AlNiZr合金組分,加入其他元素的微合金,探尋具有更高玻璃形成能力的多元鋁基非晶合金。
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