高硅铝合金钎焊碳化硅陶瓷的接头微观组织和性能研究

发布时间：2018-04-12 13:22

本文选题：SiC陶瓷 + 真空钎焊　；参考：《合肥工业大学》2017年硕士论文

【摘要】：SiC/SiC复合材料由于高温强度高、热膨胀系数低、化学稳定性和抗辐照能力好等特点被认为是核反应堆用高温部件的理想候选材料。然而,要获得大尺寸的SiC/SiC复合材料复杂构件,需要通过材料连接来实现。本文采用具有较低中子吸收截面系数的高硅铝合金钎料对SiC块体进行了真空钎焊试验。研究了硅含量对钎料的显微组织、力学性能及在SiC表面的润湿性的影响,在优化硅含量的基础上,研究了添加第三元素(Ti、Cr)对钎料及接头性能的影响。研究结果表明:(1)Al-40Si、Al-50Si和Al-60Si(wt.%)这三种钎料的微观组织均由初生Si及Al+Si共晶组织组成,并且随着Si含量的增多,初生Si的尺寸及数量均增大,合金的显微硬度也随之增加。合金的抗压强度随着Si含量的增加而减少,说明共晶组织含量越多,钎料合金抗压能力越强。三种钎料均对SiC具有良好的润湿性,而Al-50Si钎料在SiC表面的润湿角最小,说明Al-50Si是用于SiC连接的较佳成分。Al-50Si钎料钎焊连接SiC接头的剪切强度为73.76 MPa。(2)在Al-50Si钎料中加入Ti(2,6,10,14 wt.%)进行合金化改性,得到的钎料组织中除了初生Si及Al+Si共晶组织之外,还有TiSi2相。Al-50Si-xTi钎料中的Ti可减少初生Si的尺寸和数量,使组织更加均匀。随着Ti含量的增加,合金的硬度和抗压强度均逐渐增大。用含Ti的Al-50Si钎料连接SiC陶瓷的接头剪切强度均高于不加Ti的接头,并且在Ti的加入量为6 wt.%时,获得的钎焊接头剪切强度最高,为138.98 MPa。接头剪切断口断裂方式主要由脆性断裂和韧性断裂两种方式结合。(3)在Al-50Si钎料中加入Cr(2,6,10,14wt.%)进行钎料改性,合金微观组织由初生Si、Al+Si共晶组织和CrSi2组成。随着Cr含量的增加,初生Si的含量不断减少,板条状初生Si逐渐细化。合金的硬度和抗压强度随着Cr含量的增加而增大。用含Cr的Al-50Si钎料连接SiC陶瓷的接头剪切强度均高于不加Cr的接头,在Cr含量为10 wt.%时,接头的剪切强度可达186.52 MPa。接头剪切断口断裂方式主要由脆性断裂和韧性断裂两种方式结合。
[Abstract]:SiC/SiC composites are considered to be ideal candidates for high temperature components for nuclear reactors due to their high temperature strength, low thermal expansion coefficient, good chemical stability and good radiation resistance.However, in order to obtain large-scale SiC/SiC composite complex components, it is necessary to achieve by means of material connection.The vacuum brazing test of SiC block was carried out by using high silicon aluminum alloy filler metal with low neutron absorption cross section coefficient.The effects of silicon content on microstructure, mechanical properties and wettability of SiC were studied.The results show that the microstructure of the three brazing alloys is composed of primary Si and Al-Si eutectic structure. With the increase of Si content, the size and quantity of primary Si increase and the microhardness of the alloy increases.The compressive strength of the alloy decreases with the increase of Si content, which indicates that the higher the eutectic structure content, the stronger the compressive strength of the brazing alloy.All the three solders have good wettability to SiC, and Al-50Si solders have the smallest wetting angle on SiC surface.There is also Ti in TiSi2 phase. Al-50Si-xTi solder can reduce the size and quantity of primary Si and make the microstructure more uniform.The hardness and compressive strength of the alloy increase with the increase of Ti content.The shear strength of Al-50Si solder joining SiC ceramics with Ti is higher than that without Ti, and the highest shear strength of 138.98 MPA is obtained when Ti content is 6 wt.%.The fracture mode of joint shear fracture is mainly made up of brittle fracture and ductile fracture. The brazing alloy is modified by adding CrP2O6101014wt. into Al-50Si solder. The microstructure of the alloy is composed of primary Si-Al-Si eutectic structure and CrSi2.With the increase of Cr content, the content of primary Si decreases and the laminated primary Si gradually refines.The hardness and compressive strength of the alloy increase with the increase of Cr content.The shear strength of the joints with Al-50Si solder containing Cr is higher than that of the joints without Cr. The shear strength of the joints can reach 186.52 MPA when Cr content is 10 wt.%.The fracture mode of joint shear fracture is mainly composed of brittle fracture and ductile fracture.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG407

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