摘要
Al_(2)O_(3)颗粒增强铝基复合材料具有众多优异性能,使其成为汽车轻量化和电子封装等行业的首选材料。但随着Al_(2)O_(3)体积分数的增加,复合材料强度和硬度提升而塑韧性明显降低。主要是因为Al_(2)O_(3)强化相润湿性差而发生团聚现象。在Al-12Si粉末中添加不同含量的Fe_(2)O_(3)(1%与3%)粉末制坯。采用高压凝固(0.02,2.5和3 GPa)将坯料烧结。复合材料中Fe_(2)O_(3)与Al发生置换反应制得纳米级Al_(2)O_(3)颗粒。结果表明:复合材料由α-Al,β-Si,Fe_(2)O_(3)和新生成的Al_(2)O_(3)衍射峰组成,呈现“网状晶界+块状硅+基体”形貌。通过对“网状晶界”分析,发现网状晶界是由纳米级的Al_(2)O_(3)颗粒、部分未参与反应的Fe_(2)O_(3)以及反应生成的Fe相组成。在XRD图谱中无Fe相衍射峰是由于生成的Fe相含量较少并且其在Al中有一定的固溶度。另外,凝固的压力越高网状晶界越密集,Fe_(2)O_(3)含量越高网状晶界越明显。对比复合材料热膨胀系数第一次与第二次加热结果发现。第一次加热时,由于高压固溶的硅析出热膨胀系数(CTE)曲线有峰值出现。另外,由于Fe_(2)O_(3)自身的CTE值也较铝合金的小,加入Fe_(2)O_(3)含量高的材料的热膨胀系数反而较小。在第二次加热时,由于第一次加热后缓慢冷却,所以均无热膨胀系数峰值出现。并且第二次加热最大热膨胀系数值较第一次降低75%。
Al_(2)O_(3) particle reinforced aluminum matrix composites exhibit excellent properties,such as high strength,high hardness,wear resistance and low coefficient of thermal expansion,making them the preferred material in aerospace,automotive light weight and electronic packaging industries.In the production,with the increase of Al_(2)O_(3) volume in the matrix,the strength and hardness of the composites were increased,while the plastic toughness was decreased.The main reason was that the wettability of Al_(2)O_(3) strengthening phase is poor,which leads to agglomeration when entering the matrix.In this paper,the nanometer Al_(2)O_(3) particle reinforced Al matrix composites were prepared by in-situ high-pressure solidification(0.02,2.5 and 3 GPa)to refine Al_(2)O_(3) particles and make them distribute.In these composites,Al_(2)O_(3) particles were produced in-situ by the substitution reactions of Fe_(2)O_(3) and Al.Compared with Al matrix composites which were directly added Al_(2)O_(3) particles,the composites of in-situ Al_(2)O_(3) particle possessed the characteristics of excellent interface bonding,good compatibility and nano-sized particles.Then the microstructure of the composites was analyzed by scanning electron microscope(SEM),X-ray diffraction(XRD)and energy dispersive spectrometer(EDS),and the effects of microstructure on density and thermal expansion of the composites were discussed.The results showed that Fe_(2)O_(3)/Al-12Si composites were composed ofα-Al,β-Si,Fe_(2)O_(3) and new product Al_(2)O_(3).The microstructure showed that the composites were mainly composed of"nano network grain boundary+bulk silicon+matrix".Through EDS analysis of the"network grain boundary",it was found that the network grain boundary was composed of nano-sized Al_(2)O_(3) particles,some Fe_(2)O_(3) particles were not involved in the reaction and Fe phase produced by the reaction.The non-Fe diffraction peak in XRD was due to the low content of Fe phase produced and a certain solid solubility in Al.Additionally,with the increase of the pressure,the network boundaries became denser,and the higher Fe_(2)O_(3) content was,the more obvious the network grain boundaries were.In summary,the solidification process could be briefly described as follows:when the sample was heated under high pressure,and the melting point of Al was low beginning to melt and the reaction of Fe_(2)O_(3) in contact with the surrounding was accelerated.However,the displacement of atoms was limited under extremely high pressure,and Fe_(2)O_(3) could not be supplemented in time.On the other hand,the product of Al_(2)O_(3) at the melt front increased the resistance at the melt front.The final Al_(2)O_(3) ceramic phase and some unreacted Fe_(2)O_(3) were distributed at grain boundaries.Al_(2)O_(3) phase and part of Fe_(2)O_(3) that did not participate in the reaction were distributed at the grain boundary.The coefficient of thermal expansion(CTE)of Fe_(2)O_(3)/Al-12Si composites in the first heating process was different from that in the second heating process.During the first heating,the CTE of the Fe_(2)O_(3)/Al-12Si composites could be divided into three regions according to the temperature and the peak appears.The peak value was caused by the precipitation of solid solution Si in the matrix during heating.In addition,because CTE value of Fe_(2)O_(3) was also smaller than that of Al alloy,CTE value of composites with 1%Fe_(2)O_(3) content was 33.84×10^(-6)K^(-1)at 740 K,which was higher than that of the composites with 3%Fe_(2)O_(3) content of 32.83×10^(-6)K^(-1).During the second heating,no peak of the coefficient of thermal expansion occurred due to the slow cooling after the first heating,and the maximum thermal expansion coefficient of the second heating was 75%lower than that of the first heating.
作者
陈志鹏
朱冬冬
王刚
董多
王晓红
Chen Zhipeng;Zhu Dongdong;Wang Gang;Dong Duo;Wang Xiaohong(Anhui Key Laboratory of High Performance Nonferrous Metals,School of Materials Science and Engineering,Anhui Polytechnic University,Wuhu 241000,China;School of Mechanical Engineering,Quzhou University,Quzhou 324000,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2024年第4期477-486,共10页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51801112,51704001,52071188)
安徽省自然科学基金项目(2008085J23)
浙江省自然科学基金项目(LQ20E010003)
安徽省人才工程基金项目(Z17550020001)资助。
