本文選題：電沉積　切入點(diǎn)：層狀納米晶　出處：《上海電力學(xué)院》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：納米晶材料在力學(xué)性能方面表現(xiàn)出高強(qiáng)度,但在變形過(guò)程中通常展現(xiàn)出令人失望的較低的塑性,這也嚴(yán)重限制了納米晶材料在工程上的應(yīng)用。納米晶材料的低塑性也是歸因于其本質(zhì)上缺乏有效地位錯(cuò)運(yùn)動(dòng),這使得納米晶材料在變形時(shí)不能形成較大的加工硬化能力來(lái)維持塑性變形。研究表明,通過(guò)構(gòu)造含有晶粒尺寸呈現(xiàn)雙峰或多峰分布的復(fù)合結(jié)構(gòu)可以有效地改善納米晶材料的應(yīng)變硬化能力�；谏鲜鏊悸�,本文通過(guò)采用大電流密度(23A/dm2)和小電流密度(1.5A/dm2)交替變化的直流電沉積法,制備出了由大晶粒層和小晶粒層交替變化的塊體層狀納米結(jié)構(gòu)鎳。通過(guò)X射線衍射儀(XRD),掃描電子顯微鏡(SEM),透射電子顯微鏡(TEM)對(duì)鍍層的晶體結(jié)構(gòu)和形貌進(jìn)行了分析。結(jié)果表明,在1.5A/dm2電流密度下,鍍層具有(200)擇優(yōu)生長(zhǎng)織構(gòu),晶粒尺寸約為267nm,處于超細(xì)晶范疇;在23A/dm2電流密度下,鍍層無(wú)生長(zhǎng)織構(gòu),晶粒呈現(xiàn)隨機(jī)生長(zhǎng),晶粒尺寸約為45nm,處于納米晶范疇。通過(guò)持續(xù)拉伸模式,在拉伸速率4.17×10-2s-1下,層狀納米晶鎳的抗拉強(qiáng)度(ζUTS)和延伸率(δETF)達(dá)到1290MPa,12.5%。與納米晶和超細(xì)晶Ni相比,延伸率顯著提高,且保持一個(gè)適中的強(qiáng)度。加工硬化速率被保持到8%的真應(yīng)變,說(shuō)明層狀納米晶Ni的加工硬化能力得到加強(qiáng)。掃描電鏡結(jié)果顯示,層狀納米晶鎳與超細(xì)晶和納米晶Ni的形貌分別相對(duì)應(yīng),表現(xiàn)出層狀的韌窩和隆起結(jié)構(gòu)。為了研究層厚比對(duì)層狀納米結(jié)構(gòu)Ni的力學(xué)性能影響,制備了一系列不同層厚比的層狀納米晶Ni。通過(guò)拉伸數(shù)據(jù)表明,當(dāng)硬層和軟層的比值為1:1時(shí)(即時(shí)間間隔為1h-4min),此時(shí)有最佳的力學(xué)性能,抗拉強(qiáng)度和延伸率達(dá)到1415MPa,12.3%,加工硬化速率維持到真應(yīng)變9.2%。通過(guò)在一個(gè)寬的應(yīng)變速率持續(xù)拉伸模式下(0.417s-1-4.17×10-5s-1),層狀納米晶Ni(時(shí)間間隔1h-4min)表現(xiàn)出強(qiáng)的應(yīng)變速率敏感性(m:0.018,V:19b3)。對(duì)制備的層狀納米結(jié)構(gòu)Ni進(jìn)行間歇應(yīng)力釋放拉伸實(shí)驗(yàn)(應(yīng)變速率4.17×10-2s-1),延伸率提高到14.6%,說(shuō)明不同的變形模式,對(duì)納米晶材料的力學(xué)性能有很大的影響。間歇的應(yīng)力釋放緩解了在持續(xù)拉伸過(guò)程中局部的應(yīng)力集中從而提高了納米層狀晶Ni均勻變形的能力。
[Abstract]:Nanocrystalline materials exhibit high strength in mechanical properties, but in the process of deformation usually shows a disappointingly low plasticity, which severely limits the application of nanocrystalline materials in engineering. With low plasticity of nanocrystalline materials is also attributed to the nature of the lack of effective dislocation motion, which makes the in the deformation of nanocrystalline materials can form when work hardening ability to maintain large plastic deformation. The results show that the grain size is constructed containing composite structure of Shuangfeng or multi peak distribution can effectively improve the strain hardening ability of nanocrystalline materials. Based on the above ideas, this paper adopts the high current density (23A/dm2) and small the current density (1.5A/dm2) DC electrodeposition method alternately, prepared by the large grain layer and small grain layer alternating blocks of layered nanostructured nickel. By means of X ray diffraction (XRD), scanning electron The electron microscope (SEM), transmission electron microscopy (TEM) morphology and crystal structure of the coatings were analyzed. The results show that in the current density of 1.5A/dm2 coating, with (200) preferred growth texture, grain size is about 267nm, in the ultrafine grained category; in the current density of 23A/dm2 coating, no growth texture, grain show the random growth, the grain size is about 45nm, in the nanocrystalline category. Through continuous stretching mode, the stretching rate of 4.17 * 10-2s-1, the tensile strength of layered nanocrystalline nickel (zeta UTS) and elongation (delta ETF) reached 1290MPa, 12.5%. and nano crystal compared and ultra-fine Ni, elongation significantly increased and maintain a moderate strength. The work hardening rate is maintained until the true strain of 8%, that the work hardening ability of layered nanocrystalline Ni was strengthened. Scanning electron microscopy showed that the morphology of nanocrystalline nickel layer with ultrafine grained and nanocrystalline Ni respectively Should exhibit a layered dimple and uplift structure. In order to influence the mechanical properties of the layer thickness ratio of layered nano structure of Ni, the preparation of a series of different thickness ratios of layered nanocrystalline Ni. by tensile data show that when the ratio of the hard layer and the soft layer is 1:1 (i.e. the time interval is 1h-4min). This is the best mechanical properties, tensile strength and elongation reach 1415MPa, 12.3%, to maintain the true strain hardening rate of 9.2%. through a wide strain rate tensile mode (0.417s-1-4.17 * 10-5s-1), layered nanocrystalline Ni (interval 1h-4min) exhibited strong strain rate sensitivity (m:0.018. V:19b3). The layered nanostructured Ni prepared by intermittent release of stress (tensile strain rate of 4.17 * 10-2s-1), the elongation rate increased to 14.6%, indicating the different deformation modes, have great influence on the mechanical properties of nanocrystalline materials. Intermittent The stress release relieves the local stress concentration in the continuous stretching process and thus improves the ability of the homogeneous deformation of the nanocrystalline Ni.

【學(xué)位授予單位】：上海電力學(xué)院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TB383.1;TQ138.13

【參考文獻(xiàn)】

相關(guān)期刊論文 前5條

1 曹卉;芮執(zhí)元;羅德春;剡昌鋒;陳文科;;加載速率對(duì)單晶γ-TiAl裂紋擴(kuò)展影響的分子動(dòng)力學(xué)模擬[J];材料科學(xué)與工程學(xué)報(bào);2016年02期

2 黃大志;沈理達(dá);陳勁松;朱軍;;塊體金屬納米晶材料制備技術(shù)研究現(xiàn)狀[J];熱加工工藝;2014年02期

3 屠振密;胡會(huì)利;于元春;高鵬;;電沉積納米晶材料制備方法及機(jī)理[J];電鍍與環(huán)保;2006年04期

4 徐洲 ,王秀喜 ,梁海弋 ,吳恒安;納米單晶與多晶銅薄膜力學(xué)行為的數(shù)值模擬研究[J];物理學(xué)報(bào);2004年11期

5 喬桂英,荊天輔,高明,王艷,高聿為,韓東升;高速噴射電沉積塊體納米晶Co-Ni合金[J];金屬熱處理學(xué)報(bào);2004年01期

，

本文編號(hào)：1574331