萬鵬，曹達(dá)華，周瑜杰，楊玲，辛先峰，董闖

熱處理工藝對超音速火焰噴涂Al-Cu-Fe準(zhǔn)晶涂層性能影響

萬鵬1，曹達(dá)華1，周瑜杰1，楊玲1，辛先峰2，董闖2

（1.佛山市順德區(qū)美的電熱電器制造有限公司，廣東 佛山 528300； 2.大連理工大學(xué)，遼寧 大連 116024）

使用超音速火焰噴涂（HVOF）方法制備Al-Cu-Fe準(zhǔn)晶涂層，研究熱處理溫度對涂層中準(zhǔn)晶相含量和性能的影響以及封孔處理對涂層耐蝕性的改善。以304不銹鋼為基體和真空霧化Al-Cu-Fe準(zhǔn)晶粉末為熱噴涂材料，采用超音速火焰噴涂方法制備準(zhǔn)晶涂層，并進(jìn)行550～700 ℃熱處理。利用透射電鏡、掃描電鏡、光學(xué)顯微鏡、能譜分析儀和X射線衍射儀分析準(zhǔn)晶粉末和涂層的衍射花樣、微觀形貌、成分和相結(jié)構(gòu)。分別使用顯微硬度儀和電化學(xué)工作站對比測量304不銹鋼和準(zhǔn)晶涂層的硬度和耐蝕性能。粉末中二十面體準(zhǔn)晶相（I相）為主相，并伴生準(zhǔn)晶類似相（β相）。經(jīng)過超音速火焰噴涂后，涂層中I相和β相的含量分別為78.7%和21.3%，相組成與原始粉末接近。550 ℃和600 ℃熱處理1 h后，涂層中β相消失，I相占比進(jìn)一步上升，并伴隨Al2Cu（θ相）產(chǎn)生。隨著熱處理溫度繼續(xù)升高至650 ℃，β相開始重新析出；當(dāng)熱處理溫度升至700 ℃，β相占比增至13.5%。熱處理后準(zhǔn)晶涂層的最高硬度為674HV，為304不銹鋼硬度（182HV）的3.7倍。準(zhǔn)晶涂層經(jīng)過熱處理和表面封孔后，其在3.5%NaCl溶液中腐蝕的速率低于304不銹鋼。合適的熱處理溫度是制備高純準(zhǔn)晶涂層的關(guān)鍵因素，準(zhǔn)晶含量的提升有利于提高準(zhǔn)晶涂層的硬度和耐蝕性。

準(zhǔn)晶涂層；超音速火焰噴涂；熱處理；相組成；硬度；腐蝕

準(zhǔn)晶（Quasi-crystals）是一類同時(shí)具有長程有序原子排列和非晶體學(xué)旋轉(zhuǎn)對稱性的金屬間化合物[1-3]，呈現(xiàn)出一系列介于金屬與化合物之間獨(dú)特的性能，如高硬度[4]、低摩擦因數(shù)[5-6]、高耐磨性[7-8]、低表面能[9]和低導(dǎo)熱率[10]等，在耐磨、隔熱和防黏等領(lǐng)域有著巨大的應(yīng)用潛力。但準(zhǔn)晶同時(shí)具有常溫脆性和疏松的特點(diǎn)，在實(shí)際應(yīng)用中為解決這一難題并發(fā)揮其性能優(yōu)勢，一般采用在特定基體上制備準(zhǔn)晶薄膜或涂層[11-13]。常用的準(zhǔn)晶薄膜或涂層制備工藝為物理氣相沉積（PVD）[14-16]和熱噴涂[17-18]。PVD工藝制備的薄膜一般厚度較薄且沉積速率低；而熱噴涂工藝可以獲得較厚涂層，并與基體具有良好的結(jié)合力，且噴涂面積大、沉積速率高[19]。熱噴涂根據(jù)熱源的不同分為火焰噴涂、電弧噴涂和等離子噴涂。其中，超音速火焰噴涂（HVOF）采用航空煤油、丙烯、氫氣等作為燃料，與助燃劑氧氣在燃燒室燃燒并產(chǎn)生超音速高溫焰流，將噴涂粒子加熱至熔化或半熔化狀態(tài)，獲得結(jié)合強(qiáng)度高、致密性好的優(yōu)質(zhì)涂層[20-21]。與等離子噴涂相比，HVOF噴涂熱源溫度更低，可以有效防止準(zhǔn)晶顆粒氧化及準(zhǔn)晶態(tài)合金組元的燒蝕，利于制備高純度準(zhǔn)晶涂層[22]；同時(shí)，HVOF噴涂粒子速度更快，利于提升準(zhǔn)晶涂層的致密性和結(jié)合力。

當(dāng)前準(zhǔn)晶涂層研究和應(yīng)用仍面臨兩個(gè)突出問題：一方面由于準(zhǔn)晶相的形成條件要求嚴(yán)格，在準(zhǔn)晶涂層制備過程中，噴涂粉末成分偏移、噴涂工藝或基材選擇不當(dāng)?shù)纫蛩貢?huì)導(dǎo)致準(zhǔn)晶相轉(zhuǎn)變?yōu)闇?zhǔn)晶類似相和其他晶體相，進(jìn)而影響涂層性能[23-24]。傅迎慶等[25]采用爆炸噴涂制備了Al-Cu-Cr準(zhǔn)晶涂層，當(dāng)噴涂能量增加時(shí)，利于獲得高硬度的致密涂層，但也會(huì)引發(fā)低熔點(diǎn)合金組元Al的氧化燒損加劇，涂層中類似相比例增加，準(zhǔn)晶相比例降低。另一方面，熱噴涂涂層是由扁平化熔融粒子搭界而成，涂層表面不可避免地存在一定的孔隙[26]。通常情況下，隨著涂層孔隙率的增加，其耐蝕性能下降[27]。本文采用HVOF工藝制備Al-Cu-Fe準(zhǔn)晶涂層，一方面通過熱處理工藝提升涂層中的準(zhǔn)晶相比例，另一方面采用表面封孔的方式改善涂層的耐蝕性能，并研究了準(zhǔn)晶涂層中物相、微觀組織及涂層硬度、電化學(xué)性能隨熱處理溫度的變化規(guī)律。

1 試驗(yàn)

1.1 成分設(shè)計(jì)和粉末制備

根據(jù)“團(tuán)簇加連接原子”模型設(shè)計(jì)理論，選用/=1.86的[Al-Cu-Fe]二十面體結(jié)構(gòu)成分，即原子比Al63Cu25Fe12成分[28]。采用氣霧化法制粉，將Al、Cu和Fe純料按比例配制好，放入真空感應(yīng)煉爐中熔煉合金鑄錠，再將錠子放入氣霧化設(shè)備中加熱，在保護(hù)氣氛下，將鑄錠加熱到融熔狀態(tài)，利用氣體壓力將融熔態(tài)的準(zhǔn)晶合金制成粉末。利用機(jī)械振動(dòng)篩篩分出粒度為15～50 μm的Al-Cu-Fe合金粉末，用于超音速火焰噴涂。

1.2 材料及涂層制備

試樣基體選用304不銹鋼材料，先對基體除油、除銹，確?；w表面無污染，然后再用剛玉顆粒對基體進(jìn)行噴砂處理，增加基體表面粗糙度。采用鄭州立佳超音速火焰噴涂系統(tǒng)HV-8000，該系統(tǒng)使用航空煤油為燃料，在噴槍的燃燒室與氧氣混合燃燒，經(jīng)拉瓦爾噴嘴加速后，形成超音速火焰束流。送粉器在氮?dú)鈮毫ο聦?zhǔn)晶合金粉末送入燃燒室，粉末顆粒被加熱至熔化或半熔化狀態(tài)，并加速噴射到基體上沉積成致密的涂層結(jié)構(gòu)。噴涂參數(shù)如表1所示。采用氬氣氣氛的熱處理爐，熱處理溫度為550～700 ℃，保溫時(shí)間為1 h。封孔劑采用氟樹脂乳液，將樣品表面浸沒于封孔劑中5 min后進(jìn)行表面干燥，再經(jīng)過380 ℃保溫10 min進(jìn)行固化燒結(jié)。

表1 超音速火焰噴涂Al-Cu-Fe準(zhǔn)晶涂層工藝參數(shù)

Tab.1 High-velocity oxy-fuel spraying parameters for Al-Cu-Fe quasi-crystalline coatings

1.3 性能表征

采用FEI Talos F200X型透射電鏡（TEM）對粉末和涂層的衍射花樣進(jìn)行表征。采用日立TM4000plus掃描電鏡（SEM）、能譜分析儀（EDS）及ZEISS Axioscope A1光學(xué)顯微鏡觀察粉末和涂層的微觀形貌及成分分析。采用日本理學(xué)Smartlab SE型X射線衍射儀（XRD）進(jìn)行物相分析。利用MTS萬能拉伸試驗(yàn)機(jī)進(jìn)行拉伸試驗(yàn)，按照GB/T 8642《熱噴涂抗拉結(jié)合強(qiáng)度的測定》進(jìn)行測定涂層與基體的結(jié)合強(qiáng)度。采用WilsonVH1202維式顯微硬度儀測量涂層硬度，隨機(jī)選取樣品表面5個(gè)位置進(jìn)行測試，采用0.2 kg載荷和頂角為136°的金剛石方形錐壓入材料表面并保壓30 s，用載荷值除以材料壓痕凹坑的表面積得到維氏硬度值。采用電化學(xué)工作站測量涂層和基材的耐蝕性能，電解質(zhì)為3.5%NaCl溶液。

2 結(jié)果與分析

2.1 粉末分析

氣霧化法制備的Al-Cu-Fe準(zhǔn)晶粉末表面形貌的SEM照片如圖1所示。經(jīng)過統(tǒng)計(jì)，粉末粒徑范圍為15～50 μm，平均粒徑為25 μm，粉末球形度高，利于提高超音速火焰噴涂時(shí)粉末的流動(dòng)性。由于氣霧化過程中冷卻速度不同，準(zhǔn)晶合金粉末的表面含少量的衛(wèi)星顆粒[17]。

圖2為超音速火焰噴涂所采用Al-Cu-Fe準(zhǔn)晶粉末的XRD圖譜，從圖中可知準(zhǔn)晶粉末中二十面體準(zhǔn)晶相（I相）為主相，并伴生準(zhǔn)晶類似相（β相）。通過統(tǒng)計(jì)I相和β相的衍射峰面積占比，計(jì)算得到準(zhǔn)晶粉末中I相的含量為77%，β相的含量為23%。圖3a和圖3b分別為Al-Cu-Fe準(zhǔn)晶粉末的TEM明場像和衍射圖，粉末的衍射斑點(diǎn)具有5次對稱的非晶體學(xué)旋轉(zhuǎn)對稱的特性，進(jìn)一步證明了粉末中含有二十面體準(zhǔn)晶結(jié)構(gòu)。

2.2 涂層分析

圖4為超音速火焰噴涂制備的Al-Cu-Fe準(zhǔn)晶涂層截面微觀形貌，涂層厚度為330 μm，涂層無裂紋但含有一定量的孔隙。形成Al-Cu-Fe涂層孔隙的原因主要有兩個(gè)：（1）超音速火焰噴涂過程中，準(zhǔn)晶粒子經(jīng)過高溫變形、相互交錯(cuò)和堆積而成的層狀結(jié)構(gòu)，由于粒子變形不充分，在堆疊過程中形成孔隙[26]；（2）采用EDS元素分析，Al、Cu和Fe的平均原子數(shù)分?jǐn)?shù)分別為60.2%、25.5%和14.3%，基本符合設(shè)計(jì)成分（Al63Cu25Fe12），其中Al的燒蝕為4%左右。由于Al元素的熔點(diǎn)低，在高溫焰流下部分氣化，當(dāng)氣體來不及從粒子內(nèi)逸出時(shí)，在涂層內(nèi)部形成孔隙。

圖1 Al-Cu-Fe準(zhǔn)晶粉末的SEM照片

圖2 Al-Cu-Fe準(zhǔn)晶粉末的XRD圖譜

圖3 Al-Cu-Fe準(zhǔn)晶粉末TEM明場像（a）和衍射圖（b）

圖4 Al-Cu-Fe準(zhǔn)晶涂層的截面微觀形貌

采用拉伸試驗(yàn)機(jī)，對黏直徑25 mm的準(zhǔn)晶涂層樣品，測得涂層的抗拉力為17 607 N，換算得到準(zhǔn)晶涂層的結(jié)合力為36 MPa。文獻(xiàn)研究表明[28]，準(zhǔn)晶材料的室溫脆性在高溫下完全消失，具有類似于超塑性的極高塑性。超音速火焰噴涂先將準(zhǔn)晶粒子加熱至熔融或半熔融狀態(tài)，再以數(shù)倍音速的速度撞擊到噴砂處理的基材上，形成高強(qiáng)度機(jī)械結(jié)合。

2.3 涂層熱處理

圖5為準(zhǔn)晶涂層經(jīng)不同溫度熱處理后的XRD圖譜，并計(jì)算準(zhǔn)晶涂層中各個(gè)晶相的比例，如表2所示。未熱處理的涂層中I相占比為78.7%，β相占比為21.3%，涂層的相組成與原始粉末接近。經(jīng)過550 ℃和600 ℃熱處理后，涂層中β相消失，I相占比進(jìn)一步上升，并伴隨Al2Cu（θ相）產(chǎn)生。隨著熱處理溫度繼續(xù)升高至650 ℃，β相開始重新析出；當(dāng)熱處理溫度升至700 ℃，β相占比增至13.5%。說明超音速火焰噴涂制備的Al-Cu-Fe準(zhǔn)晶涂層形成準(zhǔn)晶相的最佳熱處理?xiàng)l件為550～650 ℃，在此溫度區(qū)間內(nèi)準(zhǔn)晶涂層中二十面體準(zhǔn)晶相占比高于90%。

圖5 準(zhǔn)晶涂層未熱處理及經(jīng)過不同溫度熱處理后的XRD圖譜

表2 不同溫度熱處理后準(zhǔn)晶涂層中I、β和θ的含量

Tab.2 The relative amount of I, β and θ phases for quasi-crystalline coatings annealed at different temperatures mol.%

圖6為600 ℃熱處理后的Al-Cu-Fe涂層的TEM明場像（圖6a）和衍射圖（圖6b），此區(qū)域的衍射斑點(diǎn)具有準(zhǔn)晶的5次對稱特征，表明涂層中含有二十面體準(zhǔn)晶相。

圖7為熱處理前后準(zhǔn)晶涂層的表面形貌?？梢钥闯?，未熱處理的準(zhǔn)晶涂層（圖7a）中大孔（圖中箭頭所示）的孔徑為30～40 μm；600 ℃熱處理后準(zhǔn)晶涂層（圖7b）中大孔（圖中箭頭所示）的孔徑降至15～25 μm，同時(shí)涂層的孔隙率有所降低，說明熱處理過程中準(zhǔn)晶涂層發(fā)生致密化過程。

2.4 涂層性能表征

圖8為304不銹鋼和準(zhǔn)晶涂層的維氏硬度對比，其中304不銹鋼的硬度為182HV，未熱處理準(zhǔn)晶涂層的硬度為487HV，未熱處理準(zhǔn)晶涂層的硬度是304不銹鋼的2.6倍。這是由于準(zhǔn)晶材料的力學(xué)性能與金屬間化合物類似，其結(jié)合鍵除具有金屬鍵外，還有較強(qiáng)的共價(jià)鍵成分，因此硬度比304不銹鋼高。經(jīng)過550～650 ℃熱處理后，準(zhǔn)晶涂層的硬度為586～ 674HV，此時(shí)涂層中I相占比大于90%；而隨著熱處理溫度繼續(xù)增加至700 ℃，準(zhǔn)晶涂層的硬度下降至555HV，此時(shí)準(zhǔn)晶涂層中β相不斷增加，I相占比下降。結(jié)果表明，消除準(zhǔn)晶涂層中的β相有利于提高涂層硬度。

圖6 600 ℃熱處理后的Al-Cu-Fe涂層TEM明場像（a）和衍射圖（b）

圖7 準(zhǔn)晶涂層未熱處理（a）和600 ℃熱處理后（b）的表面形貌

圖8 304不銹鋼（a）、未熱處理（b）及550 ℃（c）、 600 ℃（d）、650 ℃（e）、700 ℃（f）熱處理后的準(zhǔn)晶涂層的維氏硬度

表3為304不銹鋼與不同工藝熱處理后的準(zhǔn)晶涂層的耐蝕性對比，其中corr為材料在3.5%NaCl溶液中的自腐蝕電流密度。從表3可知，304不銹鋼的自腐蝕電流密度為1.39×10?6A/cm2，而未熱處理的準(zhǔn)晶涂層的自腐蝕電流密度為1.69×10?5A/cm2。表明未熱處理的準(zhǔn)晶涂層的耐蝕性遠(yuǎn)低于304不銹鋼，一方面是由于涂層存在準(zhǔn)晶相（I相）和準(zhǔn)晶類似相（β相）形成電偶腐蝕；另一方面是涂層中存在孔隙，NaCl溶液中的Cl?具有離子半徑小、穿透能力強(qiáng)的特點(diǎn)，會(huì)優(yōu)先從孔隙中侵入，加速涂層腐蝕。熱處理后的準(zhǔn)晶涂層的自腐蝕電流密度為2.26×10?6A/cm2，比未熱處理的準(zhǔn)晶涂層降低了1個(gè)數(shù)量級，表明涂層的耐蝕性明顯提升。原因有兩點(diǎn)：（1）準(zhǔn)晶涂層中I相占比從78.7%（未熱處理）提升至90.2%（600 ℃熱處理），降低了I相與雜質(zhì)相之間電偶腐蝕的影響；（2）熱處理后準(zhǔn)晶涂層的孔隙率降低、致密度增加，有效減少了孔隙腐蝕。由于熱處理無法完全消除涂層中的孔隙，為了進(jìn)一步提高準(zhǔn)晶涂層的耐蝕性，采用氟樹脂涂料對熱處理后的準(zhǔn)晶涂層表面進(jìn)行封孔處理，經(jīng)測試涂層的自腐蝕電流密度降低至1.07× 10?6A/cm2，表明其在3.5%NaCl溶液中的腐蝕速率低于304不銹鋼。

表3 304不銹鋼與不同工藝熱處理的準(zhǔn)晶涂層的耐蝕性對比

Tab.3 Corrosion resistance comparison between 304 stainless steel and quasi-crystalline coatings with different post-treatment parameters

3 結(jié)論

1）真空霧化制備的準(zhǔn)晶粉末中二十面體準(zhǔn)晶相（I相）為主相，并伴生準(zhǔn)晶類似相（β相）。

2）經(jīng)過超音速火焰噴涂后，涂層中I相和β相的含量分別為78.7%和21.3%，相組成與原始粉末接近。550 ℃和600 ℃熱處理1 h后，涂層中β相消失，I相占比進(jìn)一步上升，并伴隨Al2Cu（θ相）產(chǎn)生。隨著熱處理溫度繼續(xù)升高至650 ℃，β相開始重新析出；當(dāng)熱處理溫度升至700 ℃，β相占比增至13.5%。

3）未熱處理準(zhǔn)晶涂層的硬度為487HV，550～ 700 ℃熱處理后準(zhǔn)晶涂層的最高硬度為674HV，是304不銹鋼硬度（182HV）的3.7倍。準(zhǔn)晶I相硬度高于β相，消除準(zhǔn)晶涂層中的β相有利于提高涂層硬度。

4）600 ℃熱處理的準(zhǔn)晶涂層的自腐蝕電流密度比未熱處理的準(zhǔn)晶涂層降低了1個(gè)數(shù)量級，而且經(jīng)過進(jìn)一步表面封孔處理后，其在3.5%NaCl溶液中的腐蝕速率低于304不銹鋼。

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Impact of Annealing Treatment on the Properties of High-velocity Oxy-fuel Sprayed Al-Cu-Fe Quasi-crystalline Coating

1,1,1,1,2,2

(1. Foshan Shunde Midea Electrical Heating Appliances Manufacturing Co., Ltd., Guangdong Foshan 528300, China; 2. Dalian University of Technology, Liaoning Dalian 116024, China)

Quasi-crystals, being brittle and porous in bulk form, are usually prepared as coatings, especially using thermal spraying for practical applications. However, due to the strict requirements for the formation of quasi-crystalline phases, powder composition, oxidization, spraying parameter, and heat treatment condition are all involved, which makes the preparation of high purity quasi-crystalline coatings quite difficult. Among the many thermal spraying techniques, high-velocity oxy-fuel spraying (HVOF) should be a good choice for such a purpose as it has a low heat-source temperature and a high particle projection speed, which can effectively avoid the oxidation of quasi-crystalline particles, reduce the ablation of the component metals of quasi-crystalline alloys, and improve the compactness and bonding strength of the coatings. In this article, high purity quasi-crystalline coatings are prepared using HVOF process. Besides the spraying process, heat treatments are specially focused to unveil the effects of different post-annealings on the content of quasi-crystalline phase, microstructure, hardness, and corrosion resistance of the prepared coatings.

The chemical composition Al63Cu25Fe12of the icosahedral quascrystal in Al-Cu-Fe system is first selected according to the cluster-plus-glue-atom model and the electron-per-atom ratio (/),/=1.86. The pure Al, Cu and Fe metals are then melted into ingots in a vacuum induction furnace and the ingots are further atomized to make powders with particle size in the range of 15-50 μm, the average particle size with high sphericity is 25 μm. Lijia HV-8000 HVOF system is adopted to prepare quasi-crystalline coatings. The spraying parameters are as follows: the speed of spray gun is 300 mm/s, the spraying distance is 300 mm, the flow rate of aviation kerosene is 19 L/h, the flow rate of oxygen is 1 850 scfh (1 scfh=28.3 L/h), and the powder feed rate is 30-35 g/min. The as-deposited coatingsare finally annealed at 550-700 ℃ for 1 hour in argon atmosphere. The surface of annealed sample is immersed in the sealing agent for 5 min and then curedat 380 ℃ for 10 min. FEI Talos F200X transmission electron microscopy (TEM) is used to characterize the diffraction patterns. Hitachi TM4000 plus scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and ZEISS optical microscope are used to observe the microstructure and composition, respectively. Smartlab SE X-ray diffractometer (XRD) is used for phase analysis. The bonding strength is measured by MTS universal tensile testing machine. The hardness is measured by WilsonVH1202 microhardness tester. The electrochemical workstation is used to measure the corrosion resistance in 3.5wt.% NaCl solution.

Icosahedral quasi-crystal phase (I phase) is the main phase (about 77%) of the powder, as evidenced by five-fold diffraction patterns, accompanied by approximant phase β. After HVOF deposition,I phase and β phase of the as-deposited coating are 78.7% and 21.3%, respectively. The thickness of thecoating is 330 μm and the bonding strength is 36 MPa. After heat treatments at 550 ℃ and 600 ℃ for 1 hour, β phase disappears and the proportion of I phase increases further, accompanied by the formation of Al2Cu (θ phase). After heat treatments at 650 ℃ for 1 hour, β phase precipitates again. When the heat treatment temperature rises to 700 ℃, β phase proportion increases to 13.5%. After heat treatments, the highest hardness of the quasi-crystalline coating is 674HV, which is 3.7 times that of 304 stainless steel (182HV). The corrosion rate in NaCl solution of the quasi-crystalline coating after heat treatment and surface sealing is lower than that of 304 stainless steel.

In summary, high purity quasi-crystalline coatings with high compactness and good bonding strength can be prepared by high-velocity oxy-fuel spraying. Proper heat treatment temperature is the key factor to obtain high purity quasi-crystallinephase. The increase of quasi-crystalline content is beneficial to improve the hardness and corrosion resistance of the coatings.

quasi-crystalline coating; high velocity oxy-fuel spraying; heat treatment; phase structure; hardness; corrosion

TG174.442

A

1001-3660(2023)02-0422-08

10.16490/j.cnki.issn.1001-3660.2023.02.041

2022–01–07；

2022–04–02

2022-01-07；

2022-04-02

順德區(qū)科技計(jì)劃項(xiàng)目（201911220001）

Shunde District Science and Technology Project (201911220001)

萬鵬（1990—），男，博士，主要研究方向?yàn)楸砻婀こ獭?/p>

WAN Peng (1990-), Male, Doctor, Research focus: surface engineering.

萬鵬, 曹達(dá)華, 周瑜杰, 等. 熱處理工藝對超音速火焰噴涂Al-Cu-Fe準(zhǔn)晶涂層性能影響[J]. 表面技術(shù), 2023, 52(2): 422-429.

WAN Peng, CAO Da-hua, ZHOU Yu-jie, et al. Impact of Annealing Treatment on the Properties of High-velocity Oxy-fuel Sprayed Al-Cu-Fe Quasi-crystalline Coating[J]. Surface Technology, 2023, 52(2): 422-429.

責(zé)任編輯：萬長清