【摘要】：擴散焊接技術屬于壓焊的一種,與傳統焊接方式相比,具有焊接接頭質量好、焊接溫度低、引起組織性能劣化程度小等優(yōu)點。而且擴散焊接可以實現物理化學性能差別較大的異種材料之間的焊接,甚至可以焊合相互不溶解或在熔焊時會產生脆性金屬間化合物的異種材料,同時因此有著很好的應用前景。表面納米化技術是一種比較新的表面改性技術,與傳統改性技術相比也有著無可比擬的優(yōu)勢,比如技術簡單、形成的納米層不易剝落分離、不改變基體狀態(tài)等。特別是金屬材料經表面納米化后表現出很多優(yōu)異的性能,比如表面強度、硬度提高;耐腐蝕性和耐磨性提高;疲勞性能改善;表面原子擴散的能力增強等。利用納米材料的高擴散性,將表面納米化技術與擴散焊技術相結合,可以得到顯著提升材料擴散焊接接頭質量的效果。為了論證表面納米化技術對擴散焊接接頭組織和性能的影響,本文以純銅為研究對象,利用表面機械滾壓技術對純銅試樣進行表面納米化處理,并利用光學和掃描電子顯微鏡、顯微硬度計、萬能試驗機等測試手段,分析了表面納米化技術對純銅表層性能的影響,并從擴散焊接接頭的顯微組織特征、顯微硬度、剪切強度等方面,分析了表面納米化技術對純銅擴散焊接接頭質量的影響,并通過添加鎳中間層來研究鎳原子在純銅試樣中的擴散行為。本文首先利用表面機械滾壓(SMR)技術,對純銅試樣進行表面納米化處理,結果表明,隨著滾壓次數的增加,純銅表層晶粒逐漸被細化,變形區(qū)域也逐漸加深。在處理20次后,純銅表層的晶粒達到納米級別,晶粒尺寸從表層至心部呈梯度分布,純銅試樣表層的顯微硬度值也顯著提高,是基體的1.5倍。通過在300℃、400℃和500℃下分別對未經表面納米化處理的純銅母材和經表面納米化處理的純銅試樣進行擴散焊接試驗,結果表明,相同溫度下,經過表面納米化處理的純銅試樣焊縫結合程度好,焊縫接頭界面處晶粒較為細小且顯微硬度值較高,而且焊接接頭的剪切強度明顯高于未經表面納米化處理的純銅母材試樣的。隨著溫度從300℃升到400℃,兩種試樣的剪切強度都有所增高,但500℃時,由于組織劣化,剪切強度不再增加,甚至有所下降。添加鎳中間層后,300℃時,鎳中間層中銅鎳原子的相互擴散很少,隨著溫度的升高,鎳中間層逐漸消失,500℃時,銅鎳原子的相互擴散更加充分。
[Abstract]:Compared with the traditional welding method, the diffusion welding technology has the advantages of good welding quality, low welding temperature and small deterioration of microstructure and properties. Moreover, diffusion welding can be used to weld dissimilar materials with different physical and chemical properties, or even to weld dissimilar materials that are insoluble to each other or produce brittle intermetallic compounds during fusion welding. At the same time, it has a good application prospect. Surface nanocrystalline technology is a relatively new surface modification technology. Compared with traditional surface modification technology, it has unparalleled advantages, such as simple technology, the formation of nano-layer is not easy to peel off, do not change the state of the matrix, and so on. Especially after surface nanocrystalline, metal materials show many excellent properties, such as surface strength, hardness improvement, corrosion resistance and wear resistance improvement, fatigue performance improvement, surface atomic diffusion ability enhanced, and so on. By using the high diffusivity of nanomaterials and combining the surface nanocrystalline technology with the diffusion welding technology, the quality of the diffusion welded joints of the materials can be significantly improved. In order to demonstrate the effect of surface nanocrystalline technology on the microstructure and properties of diffusion welded joints, the surface nanocrystalline treatment of pure copper samples was carried out by surface mechanical rolling technique, and optical and scanning electron microscopy (SEM) were used to investigate the effect of surface nanocrystallization on the microstructure and properties of diffusion welded joints. The influence of surface nanocrystalline technology on the surface properties of pure copper was analyzed by means of microhardness tester and universal tester, and the microstructure, microhardness and shear strength of diffusion welded joints were analyzed. The effect of surface nanocrystalline technology on the quality of pure copper diffusion welded joints was analyzed, and the diffusion behavior of nickel atoms in pure copper samples was studied by adding nickel interlayer. In this paper, surface nanocrystalline treatment of pure copper samples is carried out by surface mechanical rolling (SMR) technique. The results show that with the increase of rolling times, the surface grains of pure copper are gradually refined and the deformation area is gradually deepened. After 20 times of treatment, the grain size of the surface layer of pure copper reaches nanometer level, and the grain size is gradient distribution from the surface layer to the center. The microhardness of the surface layer of pure copper sample also increases significantly, 1.5 times as much as that of the matrix. The diffusion welding experiments were carried out at 300 鈩，

本文編號：2148795