【摘要】：純銅的導電和導熱性能高,是廣泛應用于電工器件和導熱器材的功能材料。然而,由于其強度和硬度較低,在使用過程中容易因力學性能不足而發(fā)生變形,并最終導致失效,因此大大限制了其在實際中的應用。針對以上問題,本論文以商用Cr粉作為增強相,制備Cr顆粒增強Cu基復合材料,通過雙步球磨(機械研磨 機械合金化)與放電等離子燒結制備高強高硬Cu-Cr復合材料,對拓寬Cu基復合材料的應用領域具有重要意義。首先,本文分別對商用Cu粉和Cr粉在干和濕兩種條件下進行機械研磨處理。結果表明,兩種條件下機械研磨后的Cu粉粒度均增大,濕磨能夠有效抑制其顆粒的顯著粗化,并使Cu粉由樹枝狀轉變?yōu)槠瑺罘垠w,而干磨則導致其嚴重粗化,形成粗大的球狀顆粒。對于Cr粉,在兩種條件下進行機械研磨均能夠實現(xiàn)其顆粒的細化,而干磨所獲得的Cr粉比濕磨更細,且干磨后Cr粉保持不規(guī)則形狀,濕磨后則轉變?yōu)槠瑺罘垠w。采用機械研磨能夠制備納米晶Cu粉和Cr粉。與濕磨相比,干磨所獲得的晶粒尺寸更小。本文對Cu粉和Cr粉的機械研磨機理進行了探究,并分析了在濕磨和干磨條件下兩種金屬粉末形態(tài)與結構的差異。其次,將預球磨Cu粉與原始Cr粉、原始Cu粉與預球磨Cr粉分別進行機械合金化處理,以制備Cu-8 at.%Cr復合粉末。為了進行對比,在相同實驗條件下對原始Cu粉與原始Cr粉進行機械合金化處理。實驗表明,相比未經預球磨處理以及單獨預球磨Cu粉,單獨預球磨Cr粉能夠制備更細小的復合粉末,同時能獲得較高的出粉率、更窄的粉末粒度分布、更小的晶粒尺寸以及更高的Cr固溶度,因此該復合粉末具有廣闊的應用前景。本文深入研究了Cu-Cr復合粉末的機械合金化機制,包括形態(tài)的轉變、晶粒的細化以及固溶度的變化,以分析預球磨處理對后續(xù)機械合金化過程中該復合粉末形態(tài)和結構的影響。最后,對所制備的Cu-8 at.%Cr復合粉末進行放電等離子燒結處理。采用掃描電子顯微鏡,透射電子顯微鏡和X射線衍射技術對燒結塊體復合材料的組織與結構進行分析。利用壓縮和維氏硬度試驗表征該材料的力學性能。結果顯示,相比未經預球磨處理以及單獨預球磨Cu粉,單獨預球磨Cr粉所制備的復合材料中Cu基體的晶粒較細小,其平均晶粒尺寸約為82 nm。該復合材料在保持一定的致密度和電學性能的前提下,具有較高的力學性能,其維氏硬度、壓縮屈服強度和壓縮率分別是327 HV、1049 MPa和10.4%。優(yōu)異的力學性能主要是由于Cr顆粒的彌散強化、Cu基體的細晶強化以及較強的Cu/Cr結合界面。
[Abstract]:Pure copper with high conductivity and thermal conductivity is widely used as functional materials for electrical devices and thermal conductive devices. However, because of its low strength and hardness, it is easy to deform due to the lack of mechanical properties in the process of use, and ultimately lead to failure, so its application in practice is greatly limited. To solve the above problems, the commercial Cr powder was used as the reinforcing phase to prepare the cr particle reinforced Cu matrix composites. The high strength and high hard Cu-Cr composites were prepared by double step ball milling (mechanical grinding and mechanical alloying) and spark plasma sintering (SPS). It is of great significance to widen the application field of Cu matrix composites. Firstly, the commercial Cu powder and Cr powder were milled under dry and wet conditions, respectively. The results show that the particle size of Cu powder increases after mechanical grinding under both conditions. Wet grinding can effectively inhibit the obvious coarsening of Cu powder and change Cu powder from dendritic to flake powder, while dry grinding results in serious coarsening. Forming coarse globular particles. For Cr powder, the particle size can be refined by mechanical grinding under both conditions, while the Cr powder obtained by dry grinding is finer than that obtained by wet grinding, and the Cr powder keeps irregular shape after dry grinding, and changes to flake powder after wet grinding. Nanocrystalline Cu and Cr powders can be prepared by mechanical grinding. The grain size of dry mill is smaller than that of wet mill. In this paper, the mechanism of mechanical grinding of Cu powder and Cr powder is studied, and the differences of morphology and structure of the two kinds of metal powder under wet and dry grinding conditions are analyzed. Secondly, Cu-8 at.%Cr composite powder was prepared by mechanical alloying of premilled Cu powder and original Cr powder, original Cu powder and premilled Cr powder. In order to compare, the original Cu powder and the original Cr powder were treated by mechanical alloying under the same experimental conditions. The experimental results show that compared with Cu powder without pre-milling and single pre-milling, Cr powder prepared by pre-milling alone can produce smaller composite powder and obtain higher powder yield and narrower particle size distribution. Because of the smaller grain size and higher Cr solubility, the composite powder has a broad application prospect. In this paper, the mechanism of mechanical alloying of Cu-Cr composite powder is studied in depth, including morphology transformation, grain refinement and the change of solid solubility, in order to analyze the effect of pre-milling on the morphology and structure of the composite powder during subsequent mechanical alloying. Finally, the Cu-8 at.%Cr composite powder was sintered by spark plasma sintering. The microstructure and structure of sintered bulk composites were analyzed by scanning electron microscope, transmission electron microscope and X-ray diffraction. The mechanical properties of the material were characterized by compression and Vickers hardness test. The results show that the grain size of Cu matrix prepared by single premilled Cr powder is smaller than that of Cu powder prepared without or without premilling. The average grain size of Cu matrix is about 82 nm. The composite has high mechanical properties on the premise of keeping certain densification and electrical properties. Its Vickers hardness, compressive yield strength and compression ratio are 327HV1049 MPa and 10.4 MPa, respectively. The excellent mechanical properties are mainly due to the dispersion strengthening of Cr particles and the fine grain strengthening of Cu matrix and the strong Cu/Cr bonding interface.
【學位授予單位】：華南理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB331

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