氧化钇稳定氧化锆掺杂钨基合金的组织和性能研究
发布时间：2019-04-11 20:34
【摘要】：钨合金广泛应用在国防,医疗,航天等领域,可以用来制作硬质合金、铸模、穿甲弹芯、电解触头和电极等产品。氧化锆(ZrO_2)是一种化学性质非常稳定的材料,硬度和熔点极高,具有优良的热性能、机械性能、电性能及较高的耐磨损、耐腐蚀性,在机械子工业、航空工业等许多领域得到广泛应用。结合ZrO_2和W的优异性能,可以提升钨合金的室温和高温力学性能,因此开发出一种新型的ZrO_2掺杂钨合金材料成为一项重要研究。通过液-液的掺杂方式,即分别采用水热法和共沸蒸馏法结合传统粉末冶金的方法制备了氧化锆掺杂钨合金粉末,并通过压制成型,垂熔烧结,旋锻加工等工序制备出钨合金材料。对合金制备过程中不同阶段的物质元素组成,相结构转变,微观组织形貌进行分析,以及对合金性能进行分析。在水热法制备粉体过程中,pH值和ZrO_2的掺杂量对前驱粉体的形貌和粒径有着显著影响。当pH=0.5时,颗粒最为细小。ZrO_2的掺杂量增加,前驱粉体易发生结块团聚现象。煅烧后粉体由单斜相氧化钨(m-WO3)和单斜相氧化锆(m-ZrO_2)组成。还原后复合粉体主要由立方相钨(c-W)和单斜相氧化锆(m-ZrO_2)构成。随着ZrO_2掺杂量的增加,钨合金粉体粒径逐渐减小。采用共沸蒸馏法同样能够制备出颗粒细小,分布均匀的ZrO_2掺杂钨合金粉末。水热法与共沸蒸馏法制备出的粉体形貌相同,粒径有微小差异,均为亚微米级颗粒。因共沸蒸馏法易于批量化制备,本文采用共沸蒸馏法制备粉体进行后续烧结加工。经过垂熔烧结得到的烧结态钨合金,ZrO_2颗粒在基体上弥散分布,颗粒尺寸~1.2μm。氧化锆在烧结过程中发生m-ZrO_2→c-ZrO_2的晶型转变,冷却至常温后,其仍然为立方相。添加稳定剂Y_2O_3可以在常温时将ZrO_2稳定成立方晶型。烧结态钨合金晶粒尺寸约为25.0μm,旋锻使晶粒得到细化,晶粒尺寸为15.0μm。经过高温退火,晶粒发生长大至40.0μm~80.0μm。不同状态下钨合金的晶粒尺寸均随着氧化锆掺杂量的增加而减小,这是由于分布于基体晶界处的ZrO_2颗粒能够抑制晶粒向外扩散生长,起到细化晶粒的作用。随着氧化锆掺杂量的增加,钨合金致密度和硬度也在不断提高。这是因为掺杂ZrO_2能够细化晶粒,进而提高其致密度和硬度。经过旋锻加工,烧结态中缺陷可以得到改善,所以其硬度有所上升。经过高温退火后,发生再结晶,导致晶粒不断长大,所以降低了其硬度。随着氧化锆掺杂量的增加,钨合金的抗压强度不断升高。高温退火后,由于晶粒重新长大,抗压强度下降。通过SEM观察ZrO_2掺杂钨合金在室温下均为脆性断裂断口。其断口形状随着氧化锆掺杂量的不同有所改变。分布于晶界处ZrO_2颗粒的在一定程度上阻碍其沿晶断裂,提高了其屈服强度。高温压缩性能测试中,随着温度的不断升高,氧化锆掺杂钨合金棒材和纯钨棒的抗压强度不断减小。在1000℃~1200℃之间,Zr O2掺杂钨合金的抗压强度均高于纯钨棒;温度高于1200℃时,纯钨的抗压强度逐渐高于氧化锆掺杂钨合金。这是因为此温度下,钨基体与氧化锆颗粒的界面结合能力不断弱化,导致钨合金整体压缩性能下降。当在温度一定,高温压缩应变速率不同的情况下,应变速率为1/s时,其真实应力明显高于应变速率为0.01/s和0.005/s下的真实应力。应变速率越高,其抗压强度就越大,材料的塑性变形能力降低。
[Abstract]:The tungsten alloy is widely used in the fields of national defense, medical treatment, aerospace and the like, and can be used for making products such as hard alloy, casting mold, armour-piercing core, electrolytic contact and electrode. The iron oxide (ZrO _ 2) is a very stable material with very high hardness and melting point, and has excellent thermal property, mechanical property, electrical property and high wear resistance and corrosion resistance, and is widely applied in many fields such as the mechanical sub-industry, the aviation industry and the like. In combination with the excellent properties of ZrO _ 2 and W, the room temperature and high-temperature mechanical properties of the tungsten alloy can be improved, and a new type of ZrO _ 2-doped tungsten alloy material has been developed as an important research. The tungsten oxide-doped tungsten alloy powder is prepared by the method of liquid-liquid doping, that is, by adopting a hydrothermal method and an azeotropic distillation method in combination with a conventional powder metallurgy method, and a tungsten alloy material is prepared through the processes of press molding, vertical fusion sintering, rotary forging and the like. The material composition, phase structure transition, microstructure and microstructure of the alloy during the preparation of the alloy are analyzed, and the properties of the alloy are analyzed. In the preparation of the powder by the hydrothermal method, the pH value and the doping amount of ZrO _ 2 have a significant effect on the morphology and the particle size of the precursor powder. When the pH = 0.5, the particles are the most fine. The doping amount of ZrO _ 2 is increased, and the agglomeration and agglomeration of the precursor powder are easy to occur. The powder is composed of monoclinic tungsten oxide (m-WO3) and monoclinic phase oxide (m-ZrO _ 2). The composite powder is mainly composed of cubic phase tungsten (c-W) and monoclinic phase oxide (m-ZrO _ 2). With the increase of the doping amount of ZrO _ 2, the particle size of the tungsten alloy powder gradually decreases. By adopting the azeotropic distillation method, the ZrO _ 2 doped tungsten alloy powder with fine particles and uniform distribution can be prepared. The morphology of the powder prepared by the hydrothermal method and the azeotropic distillation method is the same, and the particle size is slightly different, and is all the sub-micron grade particles. In this paper, an azeotropic distillation method is used to prepare the powder for subsequent sintering. The crystal form of m-ZrO _ 2-c-ZrO _ 2 in the sintering process of the sintered tungsten alloy and the ZrO _ 2 particles which were obtained by the vertical-melting sintering and the particle size of ~ 1.2. m. The crystal form of m-ZrO _ 2-c-ZrO _ 2 in the sintering process was changed, and it was still the cubic phase after cooling to normal temperature. The addition of the stabilizer Y _ 2O _ 3 can stabilize the ZrO _ 2 at normal temperature. The grain size of the sintered tungsten alloy was about 25.0. m u.m, and the grain size was 15.0um. After high-temperature annealing, the grain size was raised to 40.0. m The ZrO _ 2 particles, which are distributed at the grain boundary of the matrix, can inhibit the growth of the crystal grains from the outside and play a role in refining the crystal grains. With the increase of the doping amount of the tungsten oxide, the density and the hardness of the tungsten alloy are also increasing. This is because the doped ZrO _ 2 can refine the crystal grains and further improve the density and the hardness of the crystal. The defects in the sintered state can be improved through the rotary forging process, and the hardness thereof is increased. After high-temperature annealing, the recrystallization is carried out, resulting in the growth of the grains, and the hardness thereof is reduced. The compressive strength of the tungsten alloy is increasing with the increase of the doping amount of the tungsten oxide. After high-temperature annealing, the compressive strength decreased due to the re-growth of the grains. The fracture of ZrO _ 2 doped tungsten alloy at room temperature was observed by SEM. The fracture shape of which changes with the doping amount of the oxide. The ZrO _ 2 particles, which are distributed at the grain boundary, prevent the grain from breaking along the crystal to a certain extent, and the yield strength thereof is improved. In the high-temperature compression performance test, the compressive strength of the tungsten oxide-doped tungsten alloy bar and the pure tungsten rod decreases with the increase of the temperature. The compressive strength of the Zr _ 2-doped tungsten alloy is higher than that of the pure tungsten rod at the temperature of 1000-1200 DEG C, and the compressive strength of the pure tungsten is gradually higher than that of the tungsten oxide-doped tungsten alloy when the temperature is higher than 1200 DEG C. This is because the interface bonding ability of the tungsten matrix and the tungsten oxide particles is continuously weakened at this temperature, resulting in a decrease in the overall compression performance of the tungsten alloy. When the strain rate is 1/ s, the true stress is obviously higher than the true stress at the strain rate of 0.01/ s and 0.005/ s when the temperature is constant and the high-temperature compressive strain rate is different. The higher the strain rate, the greater the compressive strength and the lower the plastic deformation capacity of the material.
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.411
本文编号：2456723
[Abstract]:The tungsten alloy is widely used in the fields of national defense, medical treatment, aerospace and the like, and can be used for making products such as hard alloy, casting mold, armour-piercing core, electrolytic contact and electrode. The iron oxide (ZrO _ 2) is a very stable material with very high hardness and melting point, and has excellent thermal property, mechanical property, electrical property and high wear resistance and corrosion resistance, and is widely applied in many fields such as the mechanical sub-industry, the aviation industry and the like. In combination with the excellent properties of ZrO _ 2 and W, the room temperature and high-temperature mechanical properties of the tungsten alloy can be improved, and a new type of ZrO _ 2-doped tungsten alloy material has been developed as an important research. The tungsten oxide-doped tungsten alloy powder is prepared by the method of liquid-liquid doping, that is, by adopting a hydrothermal method and an azeotropic distillation method in combination with a conventional powder metallurgy method, and a tungsten alloy material is prepared through the processes of press molding, vertical fusion sintering, rotary forging and the like. The material composition, phase structure transition, microstructure and microstructure of the alloy during the preparation of the alloy are analyzed, and the properties of the alloy are analyzed. In the preparation of the powder by the hydrothermal method, the pH value and the doping amount of ZrO _ 2 have a significant effect on the morphology and the particle size of the precursor powder. When the pH = 0.5, the particles are the most fine. The doping amount of ZrO _ 2 is increased, and the agglomeration and agglomeration of the precursor powder are easy to occur. The powder is composed of monoclinic tungsten oxide (m-WO3) and monoclinic phase oxide (m-ZrO _ 2). The composite powder is mainly composed of cubic phase tungsten (c-W) and monoclinic phase oxide (m-ZrO _ 2). With the increase of the doping amount of ZrO _ 2, the particle size of the tungsten alloy powder gradually decreases. By adopting the azeotropic distillation method, the ZrO _ 2 doped tungsten alloy powder with fine particles and uniform distribution can be prepared. The morphology of the powder prepared by the hydrothermal method and the azeotropic distillation method is the same, and the particle size is slightly different, and is all the sub-micron grade particles. In this paper, an azeotropic distillation method is used to prepare the powder for subsequent sintering. The crystal form of m-ZrO _ 2-c-ZrO _ 2 in the sintering process of the sintered tungsten alloy and the ZrO _ 2 particles which were obtained by the vertical-melting sintering and the particle size of ~ 1.2. m. The crystal form of m-ZrO _ 2-c-ZrO _ 2 in the sintering process was changed, and it was still the cubic phase after cooling to normal temperature. The addition of the stabilizer Y _ 2O _ 3 can stabilize the ZrO _ 2 at normal temperature. The grain size of the sintered tungsten alloy was about 25.0. m u.m, and the grain size was 15.0um. After high-temperature annealing, the grain size was raised to 40.0. m The ZrO _ 2 particles, which are distributed at the grain boundary of the matrix, can inhibit the growth of the crystal grains from the outside and play a role in refining the crystal grains. With the increase of the doping amount of the tungsten oxide, the density and the hardness of the tungsten alloy are also increasing. This is because the doped ZrO _ 2 can refine the crystal grains and further improve the density and the hardness of the crystal. The defects in the sintered state can be improved through the rotary forging process, and the hardness thereof is increased. After high-temperature annealing, the recrystallization is carried out, resulting in the growth of the grains, and the hardness thereof is reduced. The compressive strength of the tungsten alloy is increasing with the increase of the doping amount of the tungsten oxide. After high-temperature annealing, the compressive strength decreased due to the re-growth of the grains. The fracture of ZrO _ 2 doped tungsten alloy at room temperature was observed by SEM. The fracture shape of which changes with the doping amount of the oxide. The ZrO _ 2 particles, which are distributed at the grain boundary, prevent the grain from breaking along the crystal to a certain extent, and the yield strength thereof is improved. In the high-temperature compression performance test, the compressive strength of the tungsten oxide-doped tungsten alloy bar and the pure tungsten rod decreases with the increase of the temperature. The compressive strength of the Zr _ 2-doped tungsten alloy is higher than that of the pure tungsten rod at the temperature of 1000-1200 DEG C, and the compressive strength of the pure tungsten is gradually higher than that of the tungsten oxide-doped tungsten alloy when the temperature is higher than 1200 DEG C. This is because the interface bonding ability of the tungsten matrix and the tungsten oxide particles is continuously weakened at this temperature, resulting in a decrease in the overall compression performance of the tungsten alloy. When the strain rate is 1/ s, the true stress is obviously higher than the true stress at the strain rate of 0.01/ s and 0.005/ s when the temperature is constant and the high-temperature compressive strain rate is different. The higher the strain rate, the greater the compressive strength and the lower the plastic deformation capacity of the material.
【学位授予单位】：河南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.411
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