Al-Si-C系合金中多尺度SiCp的原位合成機制與強化行為的研究
發(fā)布時間：2019-01-11 08:29
【摘要】：本文基于液-固多相反應原理,采用碳質體法在Al-Si合金熔體中原位合成了多尺度β-SiCp,并以此制備出SiCp增強鋁基復合材料。首先,對Al-Si-C體系的熱力學和動力學分析,研究了鋁熔體中SiCp合成工藝條件,提出了多尺度SiCp的漸進式合成機制。其次,研究了鋁熔體中碳質體對SiCp形貌演變的遺傳影響,提出了原位合成SiCp的平行層狀生長和定向吸附堆垛機制,并采用基于密度泛函理論的第一性原理方法,計算分析了Al摻雜對SiC晶體結構和電子密度分布的影響,揭示了摻雜型SiCp化學鍵合與硬度的相關性。最后,基于對復合材料力學性能的分析,提出了原位合成多尺度SiCp增強Al-Si基復合材料的協(xié)同強化機制以及高溫骨架強化機制。具體來講,本文的主要研究內容有：(1)鋁熔體中多尺度SiCp原位合成機制本文系統(tǒng)研究了鋁熔體中Si濃度、碳含量、反應溫度以及保溫時間等因素對Al-Si-C反應體系中β-SiCp合成的影響,研究了原位合成SiCp的臨界反應條件。提出了原位合成多尺度SiCp的反應機制：即以Al4C3為中間過渡相的漸進式反應,由于受到Al4C3遺傳效應的影響,由此獲得的SiCp多為微米或亞微米尺度；另一種直接反應機制,即通過鋁熔體中溶解態(tài)[Si]與[C]的直接反應,合成納米尺度SiCp=對于反應體系中Cu等第三組元的影響進行研究,結果表明,Cu的添加使體系的固相線和液相線均降低,導致SiCp的原位合成溫度由約750℃降低至700℃左右,也使SiCp尺寸明顯減小,并能有效地提高復合材料的力學性能。另外,還研究了以α-SiO2作為Si源的Al-Si-SiO2-C反應體系的合成機理,并制備出原位SiCp和Al203復合增強鋁合金復合材料。(2)鋁熔體中摻雜型SiCp生長機制與化學結構的研究系統(tǒng)研究了Al-Si-C體系中SiCp形貌的演變規(guī)律,即隨著保溫時間的延長,SiCp由六角薄片狀逐漸演變成六棱臺狀,最終演變成不規(guī)則的多面體狀。晶體結構分析表明,SiC三個晶面的生長速率依次為：V{110}V{100}V{111},其平衡晶體形貌為表面自由能較低的六角薄片狀,Si與C原子優(yōu)先沿110和100晶向進行堆垛,其生長速率較快,而111晶向的生長速率最慢,最終被保留下來。鋁熔體中SiCp采用平行層狀生長和定向吸附堆垛的機制進行生長。隨著SiC中Al含量的降低,SiCp增強鋁基復合材料的布氏硬度由88.8HBW增加至109.2HBW,質量磨損率由0.371 mg/min降低至0.272mg/min。采用第一性原理理論計算了不同Al摻雜量時SiCp的化學結構,研究發(fā)現(xiàn),隨著SiCp中Al摻雜量的增加,其(011)晶面中原子排布發(fā)生變化,導致SiCp中共價鍵成分降低,碳原子周圍的電子云密度減小,摻雜型SiCp的硬度降低,建立了Al摻雜型SiC中化學鍵合與硬度之間的相關性。研究了碳質體的尺寸與種類對SiCp形貌的遺傳效應,結果表明,碳質體尺寸減小,有助于加快體系的反應速率,使其形貌更趨近于多面體形態(tài)；碳質體的形貌能夠在一定程度上對合成SiCp形貌產生遺傳影響。(3)原位合成SiCp對Al-Si系合金復合材料強化行為的研究本文采用特種碳質體制備了多尺度SiCp增強鋁合金復合材料,并測試了其洛氏硬度、耐磨性能以及熱膨脹性能,提出了多尺度SiCp的協(xié)同強化機制。采用熱等靜壓技術對復合材料進行改進,由此制備出組織致密的SiCp/ZL111復合材料,其硬度和高溫強度均提高較大。采用合金型碳質體制備了SiCp/Al-Si系合金復合材料,研究了熱處理態(tài)和熱擠壓態(tài)的高溫拉伸性能,結果發(fā)現(xiàn)：熱處理態(tài)SiCp復合材料在350℃的拉伸強度可達132MPa,并對其高溫強化機制進行了研究；熱擠壓處理破壞了復合材料中SiCp與金屬間化合物共同構筑的耐熱網狀骨架結構,大幅降低復合材料的高溫拉伸強度。
[Abstract]:In this paper, based on the principle of liquid-solid multi-phase reaction, multi-scale Al-SiCp is synthesized in the melt of Al-Si alloy by using a carbon-mass method, and the SiCp reinforced aluminum-based composite is prepared. First, the thermodynamic and kinetic analysis of the Al-Si-C system is analyzed, and the process conditions of SiCp synthesis in the aluminum melt are studied, and the progressive synthesis mechanism of multi-scale SiCp is put forward. Secondly, the genetic influence of the carbon mass in the aluminum melt on the evolution of the SiCp morphology was studied. The parallel layered growth and the directional adsorption stacking mechanism of SiCp synthesized in situ were put forward, and the first principle method based on the density functional theory was used. The effect of Al doping on the crystal structure and electron density distribution of SiC is calculated and the correlation between the chemical bond and hardness of the doped SiCp is revealed. Finally, based on the analysis of the mechanical properties of the composite, a synergistic strengthening mechanism and a high-temperature framework strengthening mechanism for the in-situ synthesis of the multi-scale SiCp-reinforced Al-Si-based composite are put forward. In particular, the main research contents of this paper are as follows: (1) In-situ synthesis of multi-scale SiCp in aluminum melt, the effect of Si concentration, carbon content, reaction temperature and heat preservation time on the synthesis of Al-SiCp in Al-Si-C reaction system is studied in this paper. The critical reaction conditions of in-situ synthesis of SiCp are studied. In this paper, the reaction mechanism of in-situ synthesis of multi-scale SiCp is put forward, that is, the gradual reaction of Al4C3 as the intermediate transition phase, because of the influence of the genetic effect of Al4C3, the obtained SiCp is in the micron or submicron scale, and the other is a direct reaction mechanism. In other words, by the direct reaction of the dissolved state[Si] and[C] in the aluminum melt, the effect of the nano-scale SiCp = on the third group of elements such as Cu in the reaction system was studied. The results showed that the addition of Cu reduced the solidus and liquidus of the system. the in-situ synthesis temperature of the SiCp is reduced from about 750 DEG C to about 700 DEG C, the size of the SiCp is obviously reduced, and the mechanical property of the composite material can be effectively improved. In addition, the synthesis mechanism of Al-Si-SiO2-C reaction system with Si-SiO2 as Si source was also studied, and the in-situ SiCp and Al203 composite reinforced aluminum alloy composites were prepared. (2) The evolution of SiCp in the Al-Si-C system was studied by the study of the growth mechanism and chemical structure of the doped SiCp in the aluminum melt. The crystal structure analysis shows that the growth rate of the three crystal planes of SiC is: V {110} V {100} V {111}, the balance crystal has a hexagonal sheet shape with lower surface free energy, Si and C atoms take precedence along 110 and 100 crystal, the growth rate is high, and the growth rate of 111 crystal is the slowest. is finally retained. SiCp in the aluminum melt is grown by a mechanism that is parallel to the layered growth and the directional adsorption of the stack. With the decrease of Al content in SiC, the Brinell hardness of SiCp reinforced aluminum-based composite was increased from 81.8HBW to 109.2HBW, and the mass wear rate was reduced from 0.371 mg/ min to 0.272mg/ min. The chemical structure of SiCp in different Al doping levels is calculated by the first principle theory, and it is found that, with the increase of the Al doping amount in SiCp, the atomic arrangement of the (011) crystal plane is changed, which leads to the reduction of the covalent component in the SiCp, and the electron cloud density around the carbon atom is reduced. The hardness of the doped SiCp is reduced, and the correlation between the chemical bond and the hardness in the Al-doped SiC is established. The genetic effect of the size and species of the carbon plastids on the morphology of SiCp is studied. The results show that the reduction of the size of the carbon mass can help to accelerate the reaction rate of the system, and make the morphology of the carbon plastids closer to the shape of the polyhedron. The morphology of the carbon plastids can have a certain degree of genetic influence on the morphology of the synthesized SiCp. (3) In-situ synthesis of SiCp to the reinforced behavior of Al-Si-based alloy composites, a multi-scale SiCp reinforced aluminum alloy composite was prepared by using special carbon plastids, and its Rockwell hardness, wear resistance and thermal expansion performance were tested, and a multi-scale SiCp co-strengthening mechanism was proposed. The composite material was improved by hot isostatic pressing, and the hardness and high temperature strength of the composite SiCp/ ZL111 composite were improved. The high-temperature tensile properties of SiCp/ Al-Si system are studied by using the alloy-type carbon plastids. The results show that the tensile strength of the heat-treated SiCp composite at 350.degree. C. can reach 132MPa, and the high-temperature strengthening mechanism is studied. the hot extrusion treatment destroys the heat-resistant net-like framework structure which is constructed by the SiCp and the intermetallic compound in the composite material, and greatly reduces the high-temperature tensile strength of the composite material.
【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TG146.21
本文編號：2406909
[Abstract]:In this paper, based on the principle of liquid-solid multi-phase reaction, multi-scale Al-SiCp is synthesized in the melt of Al-Si alloy by using a carbon-mass method, and the SiCp reinforced aluminum-based composite is prepared. First, the thermodynamic and kinetic analysis of the Al-Si-C system is analyzed, and the process conditions of SiCp synthesis in the aluminum melt are studied, and the progressive synthesis mechanism of multi-scale SiCp is put forward. Secondly, the genetic influence of the carbon mass in the aluminum melt on the evolution of the SiCp morphology was studied. The parallel layered growth and the directional adsorption stacking mechanism of SiCp synthesized in situ were put forward, and the first principle method based on the density functional theory was used. The effect of Al doping on the crystal structure and electron density distribution of SiC is calculated and the correlation between the chemical bond and hardness of the doped SiCp is revealed. Finally, based on the analysis of the mechanical properties of the composite, a synergistic strengthening mechanism and a high-temperature framework strengthening mechanism for the in-situ synthesis of the multi-scale SiCp-reinforced Al-Si-based composite are put forward. In particular, the main research contents of this paper are as follows: (1) In-situ synthesis of multi-scale SiCp in aluminum melt, the effect of Si concentration, carbon content, reaction temperature and heat preservation time on the synthesis of Al-SiCp in Al-Si-C reaction system is studied in this paper. The critical reaction conditions of in-situ synthesis of SiCp are studied. In this paper, the reaction mechanism of in-situ synthesis of multi-scale SiCp is put forward, that is, the gradual reaction of Al4C3 as the intermediate transition phase, because of the influence of the genetic effect of Al4C3, the obtained SiCp is in the micron or submicron scale, and the other is a direct reaction mechanism. In other words, by the direct reaction of the dissolved state[Si] and[C] in the aluminum melt, the effect of the nano-scale SiCp = on the third group of elements such as Cu in the reaction system was studied. The results showed that the addition of Cu reduced the solidus and liquidus of the system. the in-situ synthesis temperature of the SiCp is reduced from about 750 DEG C to about 700 DEG C, the size of the SiCp is obviously reduced, and the mechanical property of the composite material can be effectively improved. In addition, the synthesis mechanism of Al-Si-SiO2-C reaction system with Si-SiO2 as Si source was also studied, and the in-situ SiCp and Al203 composite reinforced aluminum alloy composites were prepared. (2) The evolution of SiCp in the Al-Si-C system was studied by the study of the growth mechanism and chemical structure of the doped SiCp in the aluminum melt. The crystal structure analysis shows that the growth rate of the three crystal planes of SiC is: V {110} V {100} V {111}, the balance crystal has a hexagonal sheet shape with lower surface free energy, Si and C atoms take precedence along 110 and 100 crystal, the growth rate is high, and the growth rate of 111 crystal is the slowest. is finally retained. SiCp in the aluminum melt is grown by a mechanism that is parallel to the layered growth and the directional adsorption of the stack. With the decrease of Al content in SiC, the Brinell hardness of SiCp reinforced aluminum-based composite was increased from 81.8HBW to 109.2HBW, and the mass wear rate was reduced from 0.371 mg/ min to 0.272mg/ min. The chemical structure of SiCp in different Al doping levels is calculated by the first principle theory, and it is found that, with the increase of the Al doping amount in SiCp, the atomic arrangement of the (011) crystal plane is changed, which leads to the reduction of the covalent component in the SiCp, and the electron cloud density around the carbon atom is reduced. The hardness of the doped SiCp is reduced, and the correlation between the chemical bond and the hardness in the Al-doped SiC is established. The genetic effect of the size and species of the carbon plastids on the morphology of SiCp is studied. The results show that the reduction of the size of the carbon mass can help to accelerate the reaction rate of the system, and make the morphology of the carbon plastids closer to the shape of the polyhedron. The morphology of the carbon plastids can have a certain degree of genetic influence on the morphology of the synthesized SiCp. (3) In-situ synthesis of SiCp to the reinforced behavior of Al-Si-based alloy composites, a multi-scale SiCp reinforced aluminum alloy composite was prepared by using special carbon plastids, and its Rockwell hardness, wear resistance and thermal expansion performance were tested, and a multi-scale SiCp co-strengthening mechanism was proposed. The composite material was improved by hot isostatic pressing, and the hardness and high temperature strength of the composite SiCp/ ZL111 composite were improved. The high-temperature tensile properties of SiCp/ Al-Si system are studied by using the alloy-type carbon plastids. The results show that the tensile strength of the heat-treated SiCp composite at 350.degree. C. can reach 132MPa, and the high-temperature strengthening mechanism is studied. the hot extrusion treatment destroys the heat-resistant net-like framework structure which is constructed by the SiCp and the intermetallic compound in the composite material, and greatly reduces the high-temperature tensile strength of the composite material.
【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TG146.21
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