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Study On The Microwave Joining Of Alumina Ceramic And Its Interface

Posted on:2011-01-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:S LiFull Text:PDF
GTID:1101360308954603Subject:Materials science
Abstract/Summary:PDF Full Text Request
95-Al2O3 ceramics were successfully joined by microwave selective heating in industrial microwave furnace. In this paper, temperature-rising characteristics of Al power, nano-Si powder, Al-Si alloy powder and 95-Al2O3 ceramic in a self-making microwave heating system were experimentally investigated, based on which the wetting properties and the interfacial bonding properties of Al powder, Al-Si alloy powder and nano-Si powder to 95-Al2O3 ceramics were studied. Combination the advantages of Al-Si alloy powder and nano-Si powder, ZTM ceramic composites with micro-expansive effects, consisted of ZrO2, Al-Si alloy, Al2O3,SiO2 and Y2O3 for raw materials, were successfully prepared. The ZTM ceramic composites contain the different absorbing microwave elements at different temperature. 95-Al2O3 ceramics were effectively joined by using Al power, nano-Si powder, Al-Si alloy powder and ZTM powder containing Al-Si alloy powder. The results indicate that:Al powders which are less than 100μm, nano-Si powders and Al-Si alloy powders, used as active component, absorb microwave strongly and rise in temperature over the fusion temperature. Microwave selective heating can be performed at targeted regions during joining 95-Al2O3 ceramics with the above intermediates.95-Al2O3 ceramics were effectively joined by using Al power. During microwave joining process, microwave raises the Al powder to fusion temperature, at which Al-Si alloy powder melt immediately to form molten metal. The molten metal spread over the surface of 95-Al2O3 ceramics after breaking the oxide shell into fragments. Increasing the microwave power and the impressed pressure promote the joint's forming.At the following microwave heating process: 1KW/20min→2KW/20min→3KW/20min→0KW, 95-Al2O3 ceramics were effectively joined by using nano-Si powder as interlayer. During microwave joining process, nano-Si powder absorb microwave and be heated to high temperature combining with oxidation, fusion, spreading and penetrating. The joints are formed by liquid phase. Microwave heat-treatment promotes the elemental diffusion. Al2O3 ceramic joints were obtained with unobvious bond line, homogeneous microstructure finally following the oxidazing of the interlayer. When the content of Mg is less than 5wt%, Mg will facilitate the interfacial reaction and promote the forming of joint.95-Al2O3 ceramics were effectively joined by using the Al-Si alloy powder at 2KW/20min→0KW. During microwave joining process, micrwowav raises the Al-Si alloy to fusion temperature, at which Al-Si alloy powder melt immediately to form molten metal. The molten metal fills the interfacial gaps and the in-situ oxidation of Al-Si on the interface facilitates joint formation. Because of the volumetric expansion caused by the oxidation reactions and combination reaction at the interface are too strongly to control the heating process, the flawless joint is too difficult to obtain.At the following microwave heating process: 1KW/20min→2KW/20min→3KW/20min→2KW/20min→1KW/20min→0KW, 95-Al2O3 ceramics were effectively joined by using the ZTM ceramic composites with 20wt%ZrO2, 23.7wt%Al-Si, 33wt%Al2O3, 22.3wt%SiO2 and 1wt%Y2O3 as the interlayer. Al2O3 ceramic joints were obtained with unobvious bond line, homogeneous microstructure and high micro-hardness at the interface. The bond strength, which is 324±36MPa, is near to the matrix strength. The joining mechanism of joint formation are associated with the liquid joining, in-situ oxidation reaction joining, solid reaction joining, interfacial combination reaction joining and rapid inter diffusion across the interface. At the same time, pressure promotes the formation of the joint.
Keywords/Search Tags:Microwave joining, Ceramic joining, Selective heating, Alumina, Inter-diffusion
PDF Full Text Request
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