純鎂室溫包套等通道轉(zhuǎn)角擠壓工藝設(shè)計(jì)及變形機(jī)制
發(fā)布時(shí)間：2018-11-26 09:15
【摘要】：鎂合金作為目前工程應(yīng)用中密度最輕的結(jié)構(gòu)材料，在汽車、電子、航空、航天等領(lǐng)域有重要的應(yīng)用價(jià)值。然而，鎂及鎂合金作為密排六方結(jié)構(gòu)的晶體，在室溫下只有有限的滑移系能夠開動(dòng)，所以鎂及鎂合金的室溫塑性和延展性極差，使得鎂及鎂合金在實(shí)際應(yīng)用中受到了很大的限制。細(xì)化晶粒是一種有效提高材料綜合性能的重要手段，它不僅能提高材料的塑性和延展性，同時(shí)還能進(jìn)一步提高材料的強(qiáng)度，使得材料的綜合性能得到一定的提高。等通道轉(zhuǎn)角擠壓變形是細(xì)化晶粒的一個(gè)有效手段。為避免材料在擠壓過(guò)程中開裂，鎂及絕大部分鎂合金的等通道轉(zhuǎn)角擠壓均需在200℃以上進(jìn)行，使得在變形過(guò)程中，晶粒細(xì)化的同時(shí)又伴隨一定程度的長(zhǎng)大，減弱了晶粒細(xì)化的效果。 為了充分發(fā)揮等通道轉(zhuǎn)角擠壓細(xì)化晶粒的作用，避免其高溫長(zhǎng)大，本實(shí)驗(yàn)室提出并開發(fā)了包套等徑角擠壓技術(shù)，實(shí)現(xiàn)了大塊純鎂及鎂合金在室溫下的多道次等通道轉(zhuǎn)角擠壓變形，使進(jìn)一步細(xì)化純鎂及鎂合金組織成為可能。在此基礎(chǔ)上，本文進(jìn)一步優(yōu)化了包套結(jié)構(gòu)，順利實(shí)現(xiàn)了純鎂室溫下更多道次（8道次）的等通道轉(zhuǎn)角擠壓，同時(shí)研究了純鎂在室溫包套等徑角擠壓過(guò)程中的變形機(jī)制。 該設(shè)計(jì)將經(jīng)過(guò)熱擠壓并退火處理后，，尺寸為867mm的純鎂進(jìn)行鐵套包覆，由此增大了純鎂在變形過(guò)程中所受三向壓應(yīng)力狀態(tài)，從而對(duì)純鎂起到了一定的保護(hù)作用，進(jìn)而對(duì)包套純鎂以Bc路徑、4mm/min的速度對(duì)其進(jìn)行了室溫八個(gè)道次的等通道轉(zhuǎn)角擠壓變形，從而使得純鎂組織晶粒尺寸得到了明顯細(xì)化。利用電子掃描顯微鏡（SEM）結(jié)合背散射取向成像技術(shù)（EBSD）和顯微硬度計(jì)對(duì)熱擠壓前后及退火處理后的純鎂和等通道轉(zhuǎn)角擠壓變形前后純鎂的組織、織構(gòu)、性能及變形機(jī)制做了分析，同時(shí)，在250℃下對(duì)包套純鎂做了一個(gè)道次的等通道轉(zhuǎn)角擠壓變形，并對(duì)其變形后的組織、性能和變形機(jī)制進(jìn)行了分析，與室溫下包套純鎂一道次等通道轉(zhuǎn)角擠壓后的組織、性能和變形機(jī)制做了對(duì)比。 純鎂在300℃下，經(jīng)過(guò)熱擠壓后，組織晶粒得到了明顯的細(xì)化，并形成了與擠壓方向約10°～15°的基面織構(gòu)，同時(shí)還有一些漫散的非基面織構(gòu)所形成，擠壓后的純鎂硬度有了明顯的增大。隨著對(duì)擠壓態(tài)純鎂的退火處理，織構(gòu)沒(méi)有發(fā)生明顯的變化，硬度值有所降低。 對(duì)課題組之前包套純鎂等通道轉(zhuǎn)角擠壓變形工藝進(jìn)行改進(jìn)后，成功實(shí)現(xiàn)了室溫純鎂八個(gè)道次的等通道轉(zhuǎn)角擠壓變形，獲得了表面無(wú)裂紋的純鎂試樣。通過(guò)在室溫下對(duì)純鎂的等通道轉(zhuǎn)角擠壓大塑性變形后，純鎂組織晶粒得到了明顯的細(xì)化，隨著擠壓道次的增加，純鎂組織變形量也在增加，從而更加的細(xì)化了純鎂組織的晶粒，當(dāng)經(jīng)過(guò)八個(gè)道次的室溫等通道轉(zhuǎn)角變形后，純鎂組織晶粒已經(jīng)得到了相當(dāng)顯著的細(xì)化，并且晶粒大小均勻，晶粒尺寸大約為幾百納米。隨著擠壓道次的增加，純鎂的硬度值也不斷的增大。 在250℃下對(duì)包套純鎂進(jìn)行一道次的等通道轉(zhuǎn)角擠壓變形后，與室溫下對(duì)包套純鎂進(jìn)行一道次等通道轉(zhuǎn)角擠壓變形后純鎂對(duì)比分析后發(fā)現(xiàn)：純鎂的組織晶粒要比在室溫下一道次等通道轉(zhuǎn)角擠壓后的純鎂組織晶粒大。然而，在兩種情況下，純鎂變形過(guò)程中的變形機(jī)制相同，都是主要以基面滑移為主，非基面滑移和孿生也同時(shí)發(fā)生。同時(shí)，在兩種條件下，所得到的純鎂硬度也幾乎相同。
[Abstract]:As the most light structural material in the current project, the magnesium alloy has important application value in the fields of automobile, electronics, aviation and aerospace. However, the magnesium and the magnesium alloy are used as the crystals of the hexagonal structure, and only a limited slip system can be started at room temperature, so that the room temperature plasticity and the ductility of the magnesium and the magnesium alloy are very poor, so that the magnesium and the magnesium alloy are greatly limited in the practical application. The refined crystal grain is an important means to effectively improve the comprehensive performance of the material, which not only can improve the plasticity and the ductility of the material, but also can further improve the strength of the material, so that the comprehensive property of the material can be improved. Equal channel angular pressing and deformation are an effective means to refine the crystal grains. In order to avoid the cracking of the material during the extrusion process, the equal channel corner extrusion of the magnesium and most of the magnesium alloy need to be carried out above 200 DEG C, so that during the deformation process, the grain refinement is accompanied by a certain degree of growth, and the effect of grain refining is reduced. In order to give full play to the effect of the equal channel angle extrusion to refine the crystal grain, and to avoid the high-temperature growth of the crystal grains, the laboratory puts forward and develops the diameter-angle extrusion technology such as the bag sleeve, and realizes the multi-channel angular pressing of the bulk pure magnesium and the magnesium alloy at room temperature the deformation is so as to further refine the pure magnesium and the magnesium alloy tissue to be On the basis of this, this paper further optimizes the structure of the package, and realizes the equal-channel angular extrusion of more times (8 times) at room temperature of pure magnesium, and also studies the deformation of pure magnesium in the process of extrusion of the room temperature package. The mechanism is that after hot extrusion and annealing treatment, the pure magnesium with the size of 867mm is coated with the iron sleeve, so that the three-way pressure stress state of the pure magnesium in the deformation process is increased, so that the pure magnesium plays a certain protective role, At the speed of the Bc path and the speed of 4mm/ min, the equal-channel angular pressing and deformation of eight channels at room temperature were carried out, so that the grain size of the pure magnesium was obtained. The microstructure, structure, properties and deformation mechanism of pure magnesium before and after hot extrusion and before and after hot extrusion and after annealing treatment were made by means of electron scanning microscope (SEM) and back-scatter-oriented imaging (EBSD) and microhardness tester. At the same time, at the same time, at the same time, the pure magnesium of the package is subjected to a channel angular extrusion deformation at 250 DEG C, and the microstructure, the performance and the deformation mechanism after the deformation are analyzed, and the tissue, the performance and the deformation machine after the passage angle extrusion with the pure magnesium at room temperature and the like are carried out compared with that of pure magnesium at the temperature of 300 DEG C, after hot extrusion, the grain of the tissue is obviously refined, and the base surface is formed in the direction of about 10-15 DEG with the extrusion direction, With the annealing treatment of the pure magnesium in the extruded state, there was no obvious change in the texture. and the hardness value is reduced, and after the improvement of the extrusion deformation process of the passage angle of the pure magnesium and the like before the research group, the equal-channel corner extrusion deformation of the eight channels of the room temperature pure magnesium is successfully realized, A pure magnesium sample with no crack on the surface is obtained. After the plastic deformation of the equal-channel corner of pure magnesium at room temperature, the grain of the pure magnesium alloy is obviously refined. With the increase of the extrusion channel time, the deformation amount of the pure magnesium alloy is also increased, the crystal grains of the pure magnesium organization are refined, and when the channel angles such as the room temperature and the like of the eight channels are deformed, the grain of the pure magnesium organization has been greatly refined, and the grain size is uniform, the grain size is about a few hundred nanometers. The hardness value of the magnesium is also continuously increased. When the pure magnesium of the bag is subjected to the equal-pass angular pressing and deformation at the temperature of 250 DEG C, the pure magnesium of the bag is subjected to a secondary equal-passage corner at the same temperature with the room temperature After the comparative analysis of pure magnesium after extrusion, it was found that the microstructure of pure magnesium should be more than that at room temperature. However, in both cases, the deformation mechanism in the process of pure magnesium deformation is mainly based on the base surface. The non-base slip and twinning also occur at the same time, at the same time, under both conditions
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG379
本文編號(hào)：2358111
[Abstract]:As the most light structural material in the current project, the magnesium alloy has important application value in the fields of automobile, electronics, aviation and aerospace. However, the magnesium and the magnesium alloy are used as the crystals of the hexagonal structure, and only a limited slip system can be started at room temperature, so that the room temperature plasticity and the ductility of the magnesium and the magnesium alloy are very poor, so that the magnesium and the magnesium alloy are greatly limited in the practical application. The refined crystal grain is an important means to effectively improve the comprehensive performance of the material, which not only can improve the plasticity and the ductility of the material, but also can further improve the strength of the material, so that the comprehensive property of the material can be improved. Equal channel angular pressing and deformation are an effective means to refine the crystal grains. In order to avoid the cracking of the material during the extrusion process, the equal channel corner extrusion of the magnesium and most of the magnesium alloy need to be carried out above 200 DEG C, so that during the deformation process, the grain refinement is accompanied by a certain degree of growth, and the effect of grain refining is reduced. In order to give full play to the effect of the equal channel angle extrusion to refine the crystal grain, and to avoid the high-temperature growth of the crystal grains, the laboratory puts forward and develops the diameter-angle extrusion technology such as the bag sleeve, and realizes the multi-channel angular pressing of the bulk pure magnesium and the magnesium alloy at room temperature the deformation is so as to further refine the pure magnesium and the magnesium alloy tissue to be On the basis of this, this paper further optimizes the structure of the package, and realizes the equal-channel angular extrusion of more times (8 times) at room temperature of pure magnesium, and also studies the deformation of pure magnesium in the process of extrusion of the room temperature package. The mechanism is that after hot extrusion and annealing treatment, the pure magnesium with the size of 867mm is coated with the iron sleeve, so that the three-way pressure stress state of the pure magnesium in the deformation process is increased, so that the pure magnesium plays a certain protective role, At the speed of the Bc path and the speed of 4mm/ min, the equal-channel angular pressing and deformation of eight channels at room temperature were carried out, so that the grain size of the pure magnesium was obtained. The microstructure, structure, properties and deformation mechanism of pure magnesium before and after hot extrusion and before and after hot extrusion and after annealing treatment were made by means of electron scanning microscope (SEM) and back-scatter-oriented imaging (EBSD) and microhardness tester. At the same time, at the same time, at the same time, the pure magnesium of the package is subjected to a channel angular extrusion deformation at 250 DEG C, and the microstructure, the performance and the deformation mechanism after the deformation are analyzed, and the tissue, the performance and the deformation machine after the passage angle extrusion with the pure magnesium at room temperature and the like are carried out compared with that of pure magnesium at the temperature of 300 DEG C, after hot extrusion, the grain of the tissue is obviously refined, and the base surface is formed in the direction of about 10-15 DEG with the extrusion direction, With the annealing treatment of the pure magnesium in the extruded state, there was no obvious change in the texture. and the hardness value is reduced, and after the improvement of the extrusion deformation process of the passage angle of the pure magnesium and the like before the research group, the equal-channel corner extrusion deformation of the eight channels of the room temperature pure magnesium is successfully realized, A pure magnesium sample with no crack on the surface is obtained. After the plastic deformation of the equal-channel corner of pure magnesium at room temperature, the grain of the pure magnesium alloy is obviously refined. With the increase of the extrusion channel time, the deformation amount of the pure magnesium alloy is also increased, the crystal grains of the pure magnesium organization are refined, and when the channel angles such as the room temperature and the like of the eight channels are deformed, the grain of the pure magnesium organization has been greatly refined, and the grain size is uniform, the grain size is about a few hundred nanometers. The hardness value of the magnesium is also continuously increased. When the pure magnesium of the bag is subjected to the equal-pass angular pressing and deformation at the temperature of 250 DEG C, the pure magnesium of the bag is subjected to a secondary equal-passage corner at the same temperature with the room temperature After the comparative analysis of pure magnesium after extrusion, it was found that the microstructure of pure magnesium should be more than that at room temperature. However, in both cases, the deformation mechanism in the process of pure magnesium deformation is mainly based on the base surface. The non-base slip and twinning also occur at the same time, at the same time, under both conditions
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG379
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