納米多晶鋁及其復(fù)合材料微觀變形機(jī)理的研究
發(fā)布時(shí)間：2018-11-10 15:59
【摘要】：顆粒增強(qiáng)金屬基復(fù)合材料具有優(yōu)異的性能,應(yīng)用領(lǐng)域非常廣泛。但是在實(shí)際生產(chǎn)加工過程中還存在很多問題,例如復(fù)合材料的強(qiáng)度或延展性達(dá)不到要求等,這就需要對金屬基復(fù)合材料的性能有進(jìn)一步認(rèn)識。當(dāng)前通過分子動力學(xué)方法對納米金屬及其復(fù)合材料的研究已經(jīng)受到越來越多的關(guān)注,在原子層面對納米金屬及其復(fù)合材料拉伸過程中的微觀結(jié)構(gòu)變化進(jìn)行分析,可以更清楚的了解納米金屬及其復(fù)合材料的力學(xué)性能以及變形機(jī)制。本文應(yīng)用分子動力學(xué)方法分別對金屬多晶Al和β-SiC/Al復(fù)合材料進(jìn)行拉伸行為的模擬,重點(diǎn)研究多晶Al和β-SiC/Al復(fù)合材料的力學(xué)性能和微觀變形機(jī)制。通過Voronoi方法建立了不同晶粒尺寸的多晶Al塊體模型,在此基礎(chǔ)上對其進(jìn)行拉伸模擬。弛豫后晶界處原子數(shù)比率會增加,并且隨著晶粒尺寸的減小,晶界處原子含量增加。多晶Al塊體截面的原子能量分布呈盆地狀,晶界處原子能量比內(nèi)部晶粒的要高。重點(diǎn)討論了不同晶粒尺寸對多晶Al塊體拉伸變形的影響,結(jié)合拉伸過程的能量變化情況分析了其變形機(jī)制。結(jié)果表明：隨著晶粒尺寸的減小,多晶Al塊體的屈服強(qiáng)度減小,遵循反Hall-Petch關(guān)系。晶粒尺寸較大的多晶Al塊體拉伸過程有位錯(cuò)原子產(chǎn)生,形成交叉位錯(cuò),位錯(cuò)擴(kuò)展到晶界,被晶界阻礙運(yùn)動,對材料起到強(qiáng)化作用,同時(shí)有晶界滑移和晶粒旋轉(zhuǎn)的發(fā)生；晶粒尺寸較小的多晶Al塊體拉伸過程主要是晶界處產(chǎn)生大量缺陷原子,裂紋會在大量缺陷原子處產(chǎn)生。此外,溫度的增加、應(yīng)變率的下降均使多晶Al塊體的屈服強(qiáng)度下降。建立了體積含量相同、SiC顆粒尺寸不同的多種β-SiC/Al復(fù)合材料模型,并開展拉伸模擬。通過統(tǒng)計(jì)復(fù)合材料弛豫后晶界原子數(shù)比率得知,SiC顆粒尺寸越小,晶界原子數(shù)含量越多。重點(diǎn)討論了該復(fù)合材料力學(xué)性質(zhì)的增強(qiáng)效果,并結(jié)合拉伸過程的能量曲線變化分析了材料的變形機(jī)制。結(jié)果表明：隨著SiC顆粒尺寸的減小,復(fù)合材料的屈服強(qiáng)度減小；β-SiC/Al復(fù)合材料的屈服強(qiáng)度和彈性模量與多晶Al比較均有所提高。β-SiC/Al復(fù)合材料在拉伸變形過程中,首先是基體Al在晶界處產(chǎn)生位錯(cuò)原子,并發(fā)生擴(kuò)展；應(yīng)變達(dá)到一定值,在基體Al上產(chǎn)生裂紋,裂紋靠近增強(qiáng)體SiC和基體Al之間的晶界處,而增強(qiáng)體SiC在拉伸過程不會遭到破壞。隨著溫度的增加、應(yīng)變率的下降,β-SiC/Al復(fù)合材料的屈服強(qiáng)度均減小。
[Abstract]:Particle-reinforced metal matrix composites have excellent properties and are widely used in many fields. However, there are still many problems in the process of production and processing, such as the strength or ductility of the composites can not meet the requirements, which requires further understanding of the properties of metal matrix composites. At present, more and more attention has been paid to the study of nano-metal and its composites by molecular dynamics. The microstructure of nano-metal and its composites during tensile process is analyzed at atomic level. The mechanical properties and deformation mechanism of nano-metal and its composites can be clearly understood. In this paper, the tensile behavior of metal polycrystalline Al and 尾-SiC/Al composites were simulated by molecular dynamics method, and the mechanical properties and microscopic deformation mechanism of polycrystalline Al and 尾-SiC/Al composites were studied. The polycrystalline Al block model with different grain size was established by Voronoi method, and the tensile simulation was carried out on the basis of the model. The atomic number ratio at grain boundary increases after relaxation, and the atomic content increases with the decrease of grain size. The atomic energy distribution of the polycrystalline Al block section is basin like, and the atomic energy at the grain boundary is higher than that of the inner grain. The effect of different grain sizes on the tensile deformation of polycrystalline Al bulk is discussed, and the deformation mechanism is analyzed according to the energy variation of the tensile process. The results show that the yield strength of polycrystalline Al blocks decreases with the decrease of grain size and follows the inverse Hall-Petch relationship. The larger grain size polycrystalline Al bulk tensile process produced dislocation atoms, formed the cross dislocation, the dislocation extended to the grain boundary, was hindered by the grain boundary movement, played the strengthening role to the material, at the same time, the grain boundary slippage and the grain rotation occurred. The tensile process of polycrystalline Al bulk with small grain size is mainly caused by a large number of defect atoms at grain boundaries and cracks at a large number of defect atoms. In addition, the yield strength of polycrystalline Al blocks decreases with the increase of temperature and the decrease of strain rate. Several 尾-SiC/Al composite models with the same volume content and different SiC particle size were established and the tensile simulation was carried out. It is found that the smaller the size of SiC particles, the more the number of atoms in grain boundary of composite materials after relaxation. The reinforcing effect of the mechanical properties of the composite is discussed emphatically, and the deformation mechanism of the composite is analyzed in combination with the change of the energy curve of the tensile process. The results show that the yield strength of the composite decreases with the decrease of SiC particle size. The yield strength and elastic modulus of 尾-SiC/Al composites are higher than that of polycrystalline Al composites. During the tensile deformation of 尾-SiC/Al composites, dislocation atoms are first produced at grain boundaries by matrix Al and propagated. When the strain reaches a certain value, cracks occur on the matrix Al, and the crack is near the grain boundary between the SiC and the matrix Al, while the SiC of the reinforcements will not be destroyed during the tensile process. With the increase of temperature and the decrease of strain rate, the yield strength of 尾-SiC/Al composites decreases.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB33;O614.31
本文編號：2322893
[Abstract]:Particle-reinforced metal matrix composites have excellent properties and are widely used in many fields. However, there are still many problems in the process of production and processing, such as the strength or ductility of the composites can not meet the requirements, which requires further understanding of the properties of metal matrix composites. At present, more and more attention has been paid to the study of nano-metal and its composites by molecular dynamics. The microstructure of nano-metal and its composites during tensile process is analyzed at atomic level. The mechanical properties and deformation mechanism of nano-metal and its composites can be clearly understood. In this paper, the tensile behavior of metal polycrystalline Al and 尾-SiC/Al composites were simulated by molecular dynamics method, and the mechanical properties and microscopic deformation mechanism of polycrystalline Al and 尾-SiC/Al composites were studied. The polycrystalline Al block model with different grain size was established by Voronoi method, and the tensile simulation was carried out on the basis of the model. The atomic number ratio at grain boundary increases after relaxation, and the atomic content increases with the decrease of grain size. The atomic energy distribution of the polycrystalline Al block section is basin like, and the atomic energy at the grain boundary is higher than that of the inner grain. The effect of different grain sizes on the tensile deformation of polycrystalline Al bulk is discussed, and the deformation mechanism is analyzed according to the energy variation of the tensile process. The results show that the yield strength of polycrystalline Al blocks decreases with the decrease of grain size and follows the inverse Hall-Petch relationship. The larger grain size polycrystalline Al bulk tensile process produced dislocation atoms, formed the cross dislocation, the dislocation extended to the grain boundary, was hindered by the grain boundary movement, played the strengthening role to the material, at the same time, the grain boundary slippage and the grain rotation occurred. The tensile process of polycrystalline Al bulk with small grain size is mainly caused by a large number of defect atoms at grain boundaries and cracks at a large number of defect atoms. In addition, the yield strength of polycrystalline Al blocks decreases with the increase of temperature and the decrease of strain rate. Several 尾-SiC/Al composite models with the same volume content and different SiC particle size were established and the tensile simulation was carried out. It is found that the smaller the size of SiC particles, the more the number of atoms in grain boundary of composite materials after relaxation. The reinforcing effect of the mechanical properties of the composite is discussed emphatically, and the deformation mechanism of the composite is analyzed in combination with the change of the energy curve of the tensile process. The results show that the yield strength of the composite decreases with the decrease of SiC particle size. The yield strength and elastic modulus of 尾-SiC/Al composites are higher than that of polycrystalline Al composites. During the tensile deformation of 尾-SiC/Al composites, dislocation atoms are first produced at grain boundaries by matrix Al and propagated. When the strain reaches a certain value, cracks occur on the matrix Al, and the crack is near the grain boundary between the SiC and the matrix Al, while the SiC of the reinforcements will not be destroyed during the tensile process. With the increase of temperature and the decrease of strain rate, the yield strength of 尾-SiC/Al composites decreases.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB33;O614.31
【共引文獻(xiàn)】
相關(guān)期刊論文 前1條
1 謝根全,龍述堯;考慮小尺度效應(yīng)影響的金屬納米絲彈性模量的計(jì)算[J];蘇州科技學(xué)院學(xué)報(bào)(工程技術(shù)版);2005年02期
，本文編號：2322893
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