外文翻譯--激光焊：Ag-Pd-Au-Cu合金顯微結(jié)構(gòu)和腐蝕狀態(tài)的研究在牙科領(lǐng)域的應(yīng)用【中英文文獻(xiàn)譯文】
外文翻譯--激光焊：Ag-Pd-Au-Cu合金顯微結(jié)構(gòu)和腐蝕狀態(tài)的研究在牙科領(lǐng)域的應(yīng)用【中英文文獻(xiàn)譯文】,中英文文獻(xiàn)譯文,外文,翻譯,激光,ag,pd,au,cu,合金,顯微結(jié)構(gòu),以及,腐蝕,侵蝕,狀態(tài),狀況,研究,鉆研,牙科,領(lǐng)域,應(yīng)用,利用,運(yùn)用,中英文,文獻(xiàn),譯文
西南交通大學(xué)本科畢業(yè)設(shè)計(jì)（英語文獻(xiàn)翻譯） 7
激光焊：Ag-Pd-Au-Cu合金顯微結(jié)構(gòu)和腐蝕狀態(tài)的研究在牙科領(lǐng)域的應(yīng)用
M．L．桑多斯*、H.A.accicri、vercik、guastaldi、Instituto de Qu?mica de Araraquara-UNESP, C.P. 355, 14800-900 Araraquara, 圣保羅, 巴西。
Received 10 June 2002; accepted 20 June 2002
摘要：
激光焊接方法被引進(jìn)牙科領(lǐng)域是在上世紀(jì)八十年代末期，其應(yīng)用更廉價(jià)和體積更小的設(shè)備，使用更簡單的技術(shù)，對該領(lǐng)域起到了極大的推動作用。使它能有如此廣泛應(yīng)用，是在于它將焊接過程從熱源轉(zhuǎn)換為高能量的光束，使得牙齒修補(bǔ)過程的變形降低到最小。Ag–Pd–Au–Cu合金應(yīng)用在牙齒修補(bǔ)上的理論在很早之前就提出來了，但是具體的應(yīng)用是在激光焊出現(xiàn)之后。顯微結(jié)構(gòu)分析是使用了光學(xué)顯微鏡，而抗腐蝕性是學(xué)習(xí)了傳統(tǒng)的電氣化學(xué)技術(shù)，在傳統(tǒng)電化學(xué)的基礎(chǔ)上，在口腔中模擬周圍的環(huán)境。
在焊接區(qū)發(fā)現(xiàn)一個(gè)結(jié)構(gòu)的變化：呈現(xiàn)一個(gè)源自高速冷卻的微細(xì)構(gòu)造。焊接母材在離開焊接區(qū)域處呈現(xiàn)了粗晶的微細(xì)構(gòu)造。電氣化學(xué)實(shí)驗(yàn)顯示了在焊縫和母材區(qū)域中出現(xiàn)動電位偏極化行為,在焊縫區(qū)呈現(xiàn)較高的抗腐蝕性。阻抗頻譜分析顯示成分和組織被扭曲的特點(diǎn)，呈現(xiàn)低頻區(qū)域。
D 2002 Elsevier 科學(xué) B.V. 版權(quán)所有。
關(guān)鍵字: Ag – Pd – Au – Cu; 激光; 腐蝕; 牙齒的合金
1、 導(dǎo)言
對替代合金中搜索符合牙醫(yī)的金屬，在這個(gè)過程中, 一些研究員已經(jīng)應(yīng)用Ag－Pd 使替換貴重金屬的合金, 嘗試減少費(fèi)用和改善機(jī)械的性能，并且提高抗腐性能。激光單色性、相干性、方向性極好，亮度極高。激光焊接技術(shù)采用聚焦的激光束，把很強(qiáng)的能量集中于一點(diǎn)，加熱焊縫，使局部的金屬融化，然后冷卻，凝固結(jié)合在一起。它具有以下的優(yōu)點(diǎn)：焊接熱源為光束，無需與焊接區(qū)直接接觸，可以
透過玻璃窗進(jìn)行焊接； 熱影響區(qū)小，可以獲得精確的焊接接頭，在靠近烤瓷或樹脂貼面的部位和義齒鞍基處可以直接焊接；激光束不受磁場的影響；無需包埋．省時(shí)、快速，而且可以減少包埋過程產(chǎn)生的誤差；激光焊接的所有參數(shù)，如頻率、能量級等都行預(yù)先設(shè)置并自動操作，因此初學(xué)者容易掌握；污染小 。
激光焊接產(chǎn)生一束連貫的單色集中的高能量光線，它取代了以往在牙齒修補(bǔ)中使用的常規(guī)焊接方法。電化學(xué)在腐蝕研究中很重要的表現(xiàn)在于理解它的生物適應(yīng)性和生物的功能性，當(dāng)用于臨床時(shí)，是非常容易受到外界的侵蝕的。
這個(gè)研究觀測Ag–Pd–Au–Cu合金經(jīng)過激光焊接加工后，在模擬的口腔環(huán)境中使用前后顯微結(jié)構(gòu)的變化和材料的抗腐蝕性。
2、根據(jù)實(shí)驗(yàn)：
圖1 通過光譜學(xué)顯示所研究材料的礦物成分——在一個(gè)1cm長，直徑0.27cm樣品的焊接接頭上。
激光焊接使用的設(shè)備是Dentaurum DL 20002S，它利用結(jié)晶態(tài)的ND作為光線的來源，光線的能量大約是6.08KW/ms，焊接能量約為85.12J。試樣是手工放置在有氬氣作為保護(hù)氣體的腔室中，并且大約2/3的表面被60％的激光光線滲透。
一個(gè)精確的圓盤模型是用來獲取Ag–Pd–Au–Cu合金的測試樣品和區(qū)域的組成，不僅僅是焊接區(qū)域,一些1000- buehler machine 是用來區(qū)分在激光焊焊接處理后焊接區(qū)域的母材。
焊縫區(qū)和母材裸露在外的集合表面的面積大約0.057cm。這些裸露的表面在利用表面經(jīng)過硝酸處理的，氧化鋁粒度為0.3~1AM，180~1000目的金剛砂紙打磨拋光后，使用光學(xué)方法進(jìn)行金相分析。
工作電極是從用于金相分析的試樣中來準(zhǔn)備的。開路電路相對電動勢的測量應(yīng)用在電氣化學(xué)的嘗試中，還有動電位的兩極化和電氣化學(xué)的阻抗。
每個(gè)電化電池包含一電化電池包含0.15mol（0.9%）NaCl氣溶液，使用飽和汞電極做參比系統(tǒng)和一個(gè)粗糙的圓柱當(dāng)作輔助電極。
電阻抗的測量使用該分析儀的頻率響應(yīng)solatron1255連接到一電化學(xué)截面solartron1287，并且一個(gè)10mv的振幅應(yīng)用于一個(gè)從100KHz到6MHz不等的頻率通道，從而獲得50%的頻率，這一切都是由Zplot軟件所控制的。
3、結(jié)果和討論
圖1雙性的融合微觀結(jié)構(gòu) 圖2 焊接區(qū)域的微觀結(jié)構(gòu)
圖2介紹粗粒的二相雙性的融合微觀結(jié)構(gòu)在該基底金屬的區(qū)域。
圖3顯示焊接區(qū)域使用激光焊接從高溫迅速冷卻后的微觀結(jié)構(gòu)。后面是快速冷卻使得在焊接期間微觀結(jié)構(gòu)不能夠回復(fù)到初始的兩相雙性結(jié)構(gòu)。
顯微觀察一般包括掃描電鏡和金相分析等。掃描電鏡分析是將斷口試件置于掃描電鏡下觀察其晶體結(jié)構(gòu)、斷裂特征、熔深、氣孔、熱影響區(qū)大小等。金相分析是先把焊接試件做成金相磨片，經(jīng)酸蝕、清洗、吹干后置于金相顯微鏡下，觀察其焊區(qū)組織結(jié)構(gòu)，熔深、熔化區(qū)及熱影響區(qū)大小等。Chai等惻在焊件的金相分析中發(fā)現(xiàn)，焊接組顯示出劈裂的脆性裂口形狀，而對照組則為杯狀、圓錐狀現(xiàn)象的韌性裂口．，這從微觀上反映焊件的韌性降低：在研究激光鈦焊接時(shí)發(fā)現(xiàn)激光，焊件的熱影響區(qū)晶粒較小，出現(xiàn)僅一馬氏體結(jié)構(gòu)，而在直徑為3 mm的焊接接頭均未完全焊透。
對于焊件抗腐蝕性能研究，評價(jià)方法很多，其中恒電位陽極極化技術(shù)是一種有效的耐腐蝕性體外評價(jià)方法，其優(yōu)點(diǎn)是靈敏、快速、可定量、能模擬真實(shí)情況，結(jié)合浸泡后試件機(jī)械性能的測定可以較全面地評價(jià)材料的耐腐蝕性。一些作者測試經(jīng)過激光焊接的純鈦和Ti_6Al_4V合金在空氣及人工唾液環(huán)境下疲勞和耐腐蝕試驗(yàn)，得出在兩種環(huán)境下焊件疲勞強(qiáng)度均下降，但無論在空氣還是在人工唾液中焊件抗腐蝕性能均有不同程度的提高。
圖3焊接區(qū)域電位和時(shí)間的關(guān)系 圖4陽極的極化曲線
圖4顯示了ag–pd–au–cu合金母材和激光焊接區(qū)域電位和時(shí)間的關(guān)系。穩(wěn)定電位觀察是在兩者的區(qū)域浸入三小時(shí)之后，激光焊接存在一個(gè)穩(wěn)定的電位在50mv左右。一些研究人員發(fā)現(xiàn)，通常合金的開路電位是隨著合金中貴金屬的濃度增加而升高的。
圖5顯示該極化曲線關(guān)于該陽極性能存在差異。出現(xiàn)的區(qū)域相當(dāng)于第一個(gè)超鈍化區(qū)，反之亦然。Ecor指出激光焊區(qū)域存在較高的耐腐蝕性。
圖5極化曲線性能存在的差異
該阻抗回覆發(fā)生于該開路電位、獲得在該穩(wěn)態(tài)因?yàn)樵摶捉饘賲^(qū)域、存在該出現(xiàn)獨(dú)自扭曲半圓在高處頻率。
附著體義齒與傳統(tǒng)義齒相比，具有美觀、舒適、有利基牙健康等優(yōu)點(diǎn)，但傳統(tǒng)制作方法復(fù)雜，技術(shù)要求高，且其部件為半成品，經(jīng)鑄造、拋光等工藝后精度降低，影響附著體義齒的質(zhì)量。本研究將精密機(jī)械加工技術(shù)引入口腔修復(fù)領(lǐng)域用于成品附著體的制作；探討將激光焊接技術(shù)用于附著體與義齒連接的理想焊接參數(shù)并應(yīng)用于臨床，旨在降低附著體義齒的制作成本，提高義齒精度，簡化制作步驟，促進(jìn)附著體的普及使用。 成品、半成品附著體進(jìn)行分析、研究和臨床應(yīng)用，制訂加工圖形，利用精密加工技術(shù)，制作出成品栓體栓道精密附著體，并對其精度進(jìn)行測試。應(yīng)用激光焊接技術(shù)將附著體陰陽兩部分分別焊接到義齒的活動和固定部分，并對齒科常用修復(fù)金屬激光焊接的焊接強(qiáng)度、焊接深度、熔焊區(qū)組織結(jié)構(gòu)變化以及激光焊接對烤瓷冠金瓷界面影響進(jìn)行測試分析。通過將成品附著體應(yīng)用于臨床，驗(yàn)證附著體及激光焊接的相關(guān)性能。
焊接過程就是一個(gè)復(fù)雜的過程，其中包含著相變。相變熱模型在數(shù)學(xué)上是一個(gè)強(qiáng)非線性問題，使計(jì)算發(fā)生困難。采用在熔化帶內(nèi)調(diào)整比熱來近似計(jì)算。為了得到好的收斂解，激活牛頓一拉普森方法的線性搜索。
激光焊接是快速加熱和快速冷卻過程，由于溫度梯度極高，所以材料在激光作用下，傳熱和組織轉(zhuǎn)變都有自己的特點(diǎn):固相區(qū)滿足傳導(dǎo)傳熱，液相區(qū)滿足對流傳熱，固液界面是運(yùn)動界面。在組織轉(zhuǎn)變中，材料隨著溫度的升高，發(fā)生奧氏體及固液氣相變轉(zhuǎn)化，由于材料降溫極快，所以材料隨著溫度下降，發(fā)生氣液固及奧氏體到馬氏體相變，幾乎不發(fā)生奧氏體到其它組織的轉(zhuǎn)變;由于這些特點(diǎn)導(dǎo)致數(shù)值模擬有如下難點(diǎn):首先，得到隨溫度變化的熱物性參數(shù)非常困難;其次，熔池內(nèi)溫度無法測量，溫度場結(jié)果無法實(shí)驗(yàn)驗(yàn)證:針對這些難點(diǎn)，本文采用等效熱傳導(dǎo)系數(shù)法替代對流傳熱。
4、結(jié)論
近年來，有學(xué)者對鈦的焊接方法進(jìn)行研究，并將各種焊接方法進(jìn)行比較。Roggensaek等就比較了鈦的激光焊和等離子焊，結(jié)果發(fā)現(xiàn)兩種方法焊接后的抗疲勞強(qiáng)度無差別；但是等離子焊件接頭在極限負(fù)荷下較早出現(xiàn)疲勞，顯微硬度高于激光焊；有明顯的熱改變和熱反應(yīng)區(qū)，激光焊熱改變小；兩種焊接方法均適合焊接鈦合金，但激光焊接優(yōu)于等離子焊。Manieone等比較了激光焊和紅外銅焊法對鈦的焊接效果，發(fā)現(xiàn)激光焊接的焊接區(qū)金屬結(jié)合界面均勻。沒有微孔，金相學(xué)分析含有鈦元素。而紅外銅焊的金屬界面分界明顯，焊接區(qū)含有鎳和銅。兩者的熱反應(yīng)區(qū)均有顯微結(jié)構(gòu)變化，顯微硬度均升高。激光焊接區(qū)只有鈦元素，比紅外焊接法更理想。Neo等比較了激光焊和鎢極惰性氣體保護(hù)焊兩種焊接方法對鈦的抗拉伸機(jī)械性能的影響，發(fā)現(xiàn)后者焊件經(jīng)過熱處理后屈服強(qiáng)度和彈性模量明顯高于其他組，激光焊件的屈服強(qiáng)度和極限抗張強(qiáng)度明顯降低，兩者的伸長量均明顯低于母材。有學(xué)者用4種焊接方法焊接純鈦，即激光焊、電子束焊、使用Ag—Ti焊料的銅焊和電弧焊。對焊件的顯微結(jié)構(gòu)分析表明，激光焊接區(qū)結(jié)構(gòu)是相當(dāng)完整的與母材相同的等軸晶粒，熱反應(yīng)區(qū)??；銅焊的焊接區(qū)晶粒增大并發(fā)生形態(tài)改變：電子束焊晶粒增大和形態(tài)改變程度均大于銅焊，受影響的晶粒位于整個(gè)熔焊
區(qū)，熱反應(yīng)區(qū)大；電弧焊的晶粒結(jié)構(gòu)受到破壞，形成薄層針狀的晶體結(jié)構(gòu)，使焊件的抗疲勞強(qiáng)度降低，抗拉伸能力增強(qiáng)。比較結(jié)果可以看出激光焊接的熱反應(yīng)區(qū)最小且焊后結(jié)構(gòu)最接近母材。隨著鈦的優(yōu)良性質(zhì)被廣大口腔工作者所認(rèn)識，鈦將逐漸取代現(xiàn)有口腔修復(fù)的其他金屬材料。從近幾年來對鈦及鈦合金焊接方法的研究和各種焊接方法焊接效果的比較來看，激光焊的焊接質(zhì)量最好，是目前臨床上比較滿意的焊接方法，具有很好的應(yīng)用前景。
該焊接部位存在改善微觀結(jié)構(gòu)、快速冷卻，在基底金屬焊接部位顯示一種融合粗粒的微觀結(jié)構(gòu)。ag–pd–au–cu合金存在高度耐腐蝕性為了該基底金屬和因?yàn)樵摷す夂竻^(qū)域.AgCl可能的組織于鈍化膜形式存在?？傊?，該區(qū)域的研究存在線性阻抗反應(yīng)在低頻區(qū)，包括不均勻的擴(kuò)散在內(nèi)。
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[4] J. Basualto, C. Barcelo′ , A. Gaete, Rev. Metal. (馬德里) 32 (1996) ：314– 320.
[5] P.I. Bra°nemark, G. Zarb, T. Albrektsson, 牙科組織修補(bǔ)物的綜合分析 1989 (芝加哥).
[6] K.J. Kamimoto, Jpn. Prosthodont. Soc. 31 (1987) ：1143–1156.
[7] P.C.R.D. Souza, J.C. Dinato,冷軋鋼. Beatrice, A.C. Guastaldi,M.A. Bottino, Rev. Assoc. Paul. Cir. Dent. 54 (2000) 470– 475.
[8]金屬手冊(ASM),原料特性10, (1992) ：297–320.
[9] zplot、版本1.2∶電化學(xué)的阻抗軟件、charlottesville∶scribner聯(lián)合、1995、操作說明書。
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[11] 作者. Acciari, E.N. Codaro, A.C. Guastaldi, Mater. Lett. 36
(1998) 148–151.
[12]加拿大醫(yī)學(xué)會Brett, H.A. Acciari, A.C. Guastaldi, Mater. 科學(xué)論壇 in press.
[13] 作者 Acciari, A.C. Guastaldi,加拿大醫(yī)學(xué)會. Brett, Electrochim. Acta 46 (2001) 3887– 3893.
[14] L. Lemaitre, M. Moors, A.P. Van Peteghem, J. Oral Rehabil. 16 (1989) 543.
Laser weld: microstructure and corrosion study of Ag–Pd–Au–Cu alloy of the dental application
M.L. Santos*, H.A. Acciari, L.C.O. Vercik, A.C. Guastaldi Instituto de Qu?′mica de Araraquara-UNESP, C.P. 355, 14800-900 Araraquara, Sa?o Paulo, Brazil Received 10 June 2002; accepted 20 June 2002
Abstract
The laser welding process was introduced into dentistry by the end of the 1980s, resulting on a great impulse to that area with the development of cheaper and smaller equipment, using simpler technique. This allowed greater use of that process on the confection of prostheses compared to the brazing process since the heat source for that process is a concentrated light beam of high power, which minimizes distortion problems on the prosthetic pieces. Ag–Pd–Au–Cu alloy used on the confection of dental implant prostheses was observed before and after subjection to the laser welding process.
The microstructure was analyzed with the use of optic microscopy and the corrosion resistance was studied by the traditional electrochemical techniques and by electrochemical impedance, under environmental conditions simulating the aggressiveness found in the mouth cavity. A structural change was detected on the weld area, which presented a refined microstructure deriving from the high-speed cooling.
The base metal out of the weld area presented a fusion coarse microstructure. The electrochemical essays showed differences on the potentiodynamic polarization behavior in both weld and metal base areas, indicating superior corrosion resistance in the
weld area. The impedance spectra were characterized by capacitive distorted components, presenting linear impedance in the low frequencies area. D 2002 Elsevier Science B.V. All rights reserved.
Keywords: Ag–Pd–Au–Cu; Laser; Corrosion; Dental alloys
1. Introduction
In search for alternative metal alloys for odontological purposes, some researchers have applied the AgPd alloy to substitute the gold alloys, trying to reduce costs and to improve mechanical properties and corrosion resistance [1–4]. Due to some difficulty in obtaining adaptation in prosthetic pieces, mainly the larger ones such as metallic structures molten into one piece, called cast monoblocks, the use of welding is necessary since this technique accepts the work with segments of the prosthesis, which makes possible a balanced force distribution and the best suitable adaptation, occurring in an accurate passive way
[4,5].
The process of laser welding produces a coherent, monochromatic, concentrated light beam of high power, and it has been applied to substitute the brazing in odontological prostheses welding. The laser welding process was introduced into dentistry by the end of the 1980s, resulting on agreat impulse to the area with the development of cheaper and smaller equipment due to its advantages and wide application, which made possible to use welding in a wide variety of metals and prostheticpieces [6].
The use of electrochemical techniques in the corrosion study is important for the understanding of its performance, biocompatibility and biofunctionality, when clinically applied, for these are constantly exposed to aggressive environments.
This research observes Ag–Pd–Au–Cu alloy microstructure behavior and the material’s resistance to corrosion under environmental conditions simulating the aggressiveness found in the mouth cavity, when used on dental implant prostheses before and after
subjected to the laser welding process.
2. Experimental
Table 1 presents the mineral composition of the studied material, using Wave Dispersive Spectroscopy—WDS. The cylindrical test specimens, with 0.27-cm diameter and 1.0-cm length, have been subjected to the welding process on butt joints [7]. The welding machine, Dentaurum DL 20002S, used for the laser welding, uses a crystal NdYAG as source of laser, and the beam power was approximately 6.08 kW in 14 ms, originating a welding energy of approximately 85.12 J. The test specimens were manually placed in the chamber, with shield atmosphere of argon, and spots of lap welding, in approximately 2/3 of the surfaces, were applied in the whole section of the joint, with 60% of beam penetration. A precise disc model 15 HC DIAMOND was used to obtain the test specimens of Ag–Pd–Au–Cu alloy with area comprehending only the welding area, and an ISOMET 1000-BUEHLER machine was used to separate the base metal from the welding area after the laser process. The exposed geometric
areas of the welding cord and of the base metal were 0.057 cm2. The metallographic analysis of the exposed surface of the base metal and the welding area was done with optic microscopy, after polish
with emery cloth from 180 to 1000 mesh, alumina with granulation 1 and 0.3 Am and nitro-muriatic acid application [8]. The work electrodes were prepared from the test specimens used on the metallographic analysis. Measures of open circuit potential versus
time were used in the electrochemical essays, as well as potentiodynamic polarization and electrochemical impedance. An electrochemical cell containing NaCl 0.15 mol l _ 1 (0.9%) airy solution with three electrodes was also used, with the saturated calomel electrode (SCE) as reference system and a graffiti cylinder as auxiliary electrode. Electrochemical measures of corrosion were done with a potentiometer Solartron SI1287. Potentiodynamic
polarization curves were observed at 0.001 V s _ 1 immediately. Impedance measures were done with the analyzer of frequency response, Solartron 1255, connected to an electrochemical interface, Solartron 1287, and an amplitude of 10 mV was applied to a frequency channel that varied from 100 kHz to 6 MHz,obtaining five points for each frequency decade, controlled
by the software Zplot [9]. The software Zveiw [10] was responsible for the adjustments
3. Results and discussion
Fig. 1 presents a coarse biphasic fusion microstructure in the base metal area.
Fig. 2 illustrates a refined dendritical microstructure in the laser weld area, deriving from the high speedy cooling imposed by the laser weld because of a located fusion process, followed by a quick cooling during the welding, which does not allow the microstructure to return to its initial biphasic structure.
Fig. 3 shows the open circuit potential versus time curves for the base metal and laser weld areas of the Ag–Pd–Au–Cu alloy. The stabilization of the potential was observed 3 h after immersion for both areas, and the laser weld presented a stabilization potential 50 mV higher. Some AgPd alloy researchers have observed that, usually, an alloy open circuit potential increases with the increase of the noble metals concentration[1].
show minute details the observation
Show minute details the observation to include to scan to give or get an electric shock the mirror and golds generally mutually analytical wait.
Scanning to give or get an electric shock the mirror analysis is to will break the oral test piece to place in scan to give or get an electric shock the mirror observation
Its crystal structure, split the characteristic,deep, pore, hot influence area Size etc..The gold is mutually analytical to try the piece to the welding to make into the gold first to whet mutually Slice, through the sour eclipse, clean, blow the stem to postpose is mutually the microscope in the gold next,Observe its area organization structure, the is deep and melts the area and hot influence areas
Size etc..Chai etc. the is in the gold of the piece of mutually analytically detection, Connect the set displays the brittleness open wound shape of split the , but matched control then is .
The tenacity open wound of the cup form, the cone form phenomenon., this is from the tiny view last reflection
The tenacity of the piece of lower:Discover the laser while study the laser welding
The hot influence area grain of the piece of is smaller, appearing only one horse surname body structure,
But deal with contact for the welding of the 3 mms at the diameter all the not yet finished whole is deeply
The polarization curves on Fig. 4 present differences on the anodic behavior, with the occurrence of an area corresponding to the first transpassive region
close to + 0.07 V (SCE) on the laser weld. The numbers obtained for the corrosion potentials, Ecor, indicate that the laser weld area presents higher
corrosion resistance.The impedance responses originated in the open
circuit potential, obtained in the steady state for the base metal area, present the occurrence of one distorted semicircle at high frequencies (Fig. 5).
The equivalent electrical circuit model better adjustable to the characteristics of the resulting spectrum is composed of a parallel association of RTC and
CPE, which represents the electrochemical behavior of the interface in the high frequencies area, include-including only one charge transfer process. In the low frequencies areas, the spectrum is controlled by the
occurrence of a straight line, and a new Rp and CPEp composition was used to represent the formation of a permeable nature interface since this dispersion, observed during the frequency variation, may have been originated from the formation of pits on the surface, thus confirmed by the optic microscopy analysis after the corrosion essays (not showed) and by the significant decrease on the polarization resistance number from around 10 kV cm2 to 100 V cm2 (Table 2). According to the
correspondent impedance diagrams obtained with the Bode format, fair concordance between the experimental and calculated numbers is observed.
The use of one CPE to substitute the double electrical layer is due to a correction of the distortions caused by the uniformity in the current
distribution caused by the geometry of the electrodic surface [11–13]. A diffusion process represented
by a straight line on the complex plane and by the distortion degree, ac0.5 (Table 2), is observed at low frequencies.
The laser welded joint area presented two distorted semicircles within the studied frequency channel (Fig. 6). For that reason, an equivalent electrical circuit model with two series RC terms was proposed. On the laser weld, Rp2 was considerably higher than Rp1 (Table 3), with the occurrence of a passive nature layer, formed from the corrosion
products themselves.
Fig. 6 also presents the corresponding Bode formats.
According to the variation of the phase angle versus frequency, the first maximum point is observed close to 20j. Lemaitre et al. [14] have observed that a phase angle of 22.5j, half of 45j (free diffusion of the
species in solution), may indicate diffusion due to some specific type of pore, which can be taken into account in this case because of this alloy’s permeable nature.
4. Conclusions
The weld area presented refined microstructure, deriving from the high speedy cooling, while the base metal out of the weld area showed a fusion coarse microstructure.
The Ag–Pd–Au–Cu alloy presented high corrosion resistance both for the base metal and for the laser weld areas. AgCl probably forms the passiveness films occurring in both circumstances.
In general, all the areas studied presented linear impedance response at low frequencies, including a non-uniform diffusion. The Ag–Pd–Au–Cu laser alloy impedance responses were adjusted by an equivalent electrical circuit model involving two series RC terms with
Rp2{Rp1 and the Rp numbers varied from 10 to 103 V cm2.
On the base metal area of the Ag–Pd–Au–Cu alloy, the impedance responses at low frequencies were interpreted from a model that considers the occurrence of a pore layer.
The dentistry material laser welding method and other welding methodses compare In recent years, have the scholar to the of welding method carry on the research,Combine to carry on various welding method comparison.The Roggensaek waits the old comparison Laser and etc.s ion of the , as a result discover two kinds of methods Tired strength indiscrimination of anti- connect behind;But etc. the ion piece deal with contact
Carry in the extreme limit under compare to appear early tired, show minute details the degree of hardness high in laser
Have obviously of hot the change responds the area with heat, the laser hot change Small Two kinds of welding methods are all in keeping with to weld the metal alloy, but laser Connect better than etc. ion .Manieone etc. compared the laser and Welding result of the red and outside copper method to , discover the of the laser welding Connect the area metals combines the interface even.Has no tiny bore, the gold learns the analysis mutually
Imply the chemical element of .But the metals interface boundary of the red and outside copper is obvious, Weld the area implies the and coppers.Both of hot reaction area all show minute details the knot.
The variety, show minute details the degree of hardness to all go up.The laser welding area onlies have the dollar of Vegetable, more more ideal than red outside welding method.Neo etc. deleted to compare the laser
The and the pole sloth air protections are two kinds of weld the method to the of anti-Pull the influence of stretch the machine function, discover that the latter piece is through hot processing
Accept defeat the strength and flexible mold quantities behind obvious high in other set, laser
The piece accepts defeat the strength and a strength of the extreme limit anti-s to lower obviously, both of the elongation quantity is obvious all low in female material.There is scholar use 4 kinds of welding method
Welding pure , namely laser , electron beam , usage Ag- Ti Copper and the electricity s of anticipate.Show the microstructural analysis watch to the piece of Clear, the laser welding area structure is a very complete and female material same Wait the stalk grain, the hot reaction area is small;The welding area the grain of the copper enlarge
Erupt to living the appearance change:The electron beam grain enlarge and appearance change.
The degree is is all big in the copper , the grain of that is subjected to the influence locates the whole Area, the hot reaction area is big;A structure of that gives or get an electric shock the is subjected to the breakage,Become the crystal structure of the thin layer needle form, make the tired strength of the anti- of the piece of Lower, the anti- pulls to stretch the ability to build up.
More the result can see a laser Welding of structure near to most the female material after the hot reaction area least.
Was along with the good property of the recognize by the large mouth cavity worker Know, the will replace other metals material of the existing mouth cavity repair gradually Anticipate.
From weld the research of method to the and metal alloy of in the last few years.
The comparison that various welding method welds the result to see, the of the laser Connect the quantity best, is clinical currently up more satisfied welding square Method, have the good and applied foreground.
References
[1] L. Niemi, R.I. Holland, J. Dent. Res. 63 (1984) 1014– 1018.
[2] C.J. Goodacre, J. Prosthet. Dent. 62 (1989) 34– 37.
[3] J.M. Meyer, L. Reclaru, J. Mater. Sci., Mater. Med. 6 (1995)
534– 540.
[4] J. Basualto, C. Barcelo′ , A. Gaete, Rev. Metal. (Madrid) 32
(1996) 314– 320.
[5] P.I. Bra°nemark, G. Zarb, T. Albrektsson, Tissue-Integrated
Prostheses Osseointegration in Clinical Dentistry, 1989 (Chicago).
[6] K.J. Kamimoto, Jpn. Prosthodont. Soc. 31 (1987) 1143–1156.
[7] P.C.R.D. Souza, J.C. Dinato, C.R.S. Beatrice, A.C. Guastaldi,
M.A. Bottino, Rev. Assoc. Paul. Cir. Dent. 54 (2000) 470– 475.
[8] Metals Handbook (ASM), Materials Characterization 10,(1992) 297–320.
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Manual.
[11] H.A. Acciari, E.N. Codaro, A.C. Guastaldi, Mater. Lett. 36
(1998) 148–151.
[12] C.M.A. Brett, H.A. Acciari, A.C. Guastaldi, Mater. Science
Forum, in press.
[13] H.A. Acciari, A.C. Guastaldi, C.M.A. Brett, Electrochim. Acta
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