低温大载荷冲击下纯铜和工业纯铁的微观组织与性能研究
发布时间：2018-11-09 07:28
【摘要】：与传统粗晶材料相比,块体超细晶(UFG)材料由于具有更加出色的力学性能和物理性能,成为当前材料领域的研究热点之一。强烈塑性变形(SPD)由于具有良好的晶粒细化能力,成为当前块体超细晶材料制备最常用的方法之一。近些年来,一些低温强烈塑性变形技术如低温轧制、低温多向锻造、低温高压扭转、低温等通道转角挤压等成功应用于块体超细晶材料的制备。与中高温强烈塑性变形相比,低温能够有效抑制动态回复过程,促进材料内部位错的有效积累,诱导机械孪晶的产生,从而提高晶粒细化的效率,在较低的应变量下得到超细晶组织。低温大载荷冲击变形是一种潜在的用来制备块体超细晶材料的新方法。与常见的强烈塑性变形方法相比,工艺简单、无需特殊的设备,有望制备大尺寸的块体超细晶材料,具有良好的工业应用前景。但目前关于低温大载荷冲击变形制备块体超细晶材料的研究还十分有限。因此,系统的开展块体金属材料在低温大载荷冲击下的微观结构演变与性能研究十分有意义。本文利用金相分析、TEM、XRD、显微硬度、极化曲线等表征手段系统研究了具有FCC结构纯铜和具有BCC结构的工业纯铁两种金属材料在低温大载荷冲击变形后的微观组织演变和腐蚀性能以及随后退火处理对微观组织结构和性能的影响。主要研究成果如下：(1)开展纯铜低温大载荷冲击变形实验,并成功制备出具有板条状结构的块体超细晶纯铜材料。当应变量为2.21时,从横截面观察晶粒为等轴状,尺寸为150-450 nm；从纵截面观察为板条状,宽度为30-220nm。微观组织研究表明,纯铜低温大载荷冲击晶粒细化是位错胞演变机制、动态再结晶机制和孪晶细化机制三者协同作用的结果；(2)经过190℃退火60min后,纯铜发生再结晶,高密度位错消失,晶界清晰平直,晶粒在横截面上仍为等轴状,尺寸变为200-450 nm；纵截面上仍为板条状,宽度为70-100nm,此外纵截面上还观察到大量的退火纳米孪晶,孪晶的宽度为10～100 nm；(3)经过低温大载荷冲击后,纯铜在0.5 M NaCl溶液中的腐蚀速率降低；经过190℃退火60 min后,试样的腐蚀速率进一步降低；(4)开展工业纯铁低温大载荷冲击变形实验,并成功制备出具有板条状结构的块体超细晶工业纯铁材料。当应变量为2.21时,从横截面观察晶粒为等轴状,尺寸为100-300nm；从纵截面观察为板条状,宽度为100-350nm。微观组织研究表明,工业纯铁低温大载荷冲击晶粒细化主要是由晶粒破碎机制和位错胞细化机制协同作用来完成的。此外,渗碳体的存在也对工业纯铁的晶粒细化起到一定的促进作用；(5)经过500℃退火60 min以后,工业纯铁内部位错密度明显降低,晶粒轮廓清晰,晶粒在横截面上仍为等轴状,尺寸变为120-310nm；纵截面上仍为板条状,宽度变为80～350nm。与纯铜不同的是,退火处理后没有观察到退火孪晶组织；(6)经过低温大载荷冲击后,工业纯铁在0.5 M NaCl溶液中的腐蚀速率降低,钝化电流减小,钝化区间变宽,钝化能力得到明显改善；经过500℃退火60 min后,虽然腐蚀速率增大,但钝化区间进一步增加,钝化电流更加平稳,说明退火处理后工业纯铁的钝化能力得到进一步改善,钝化膜更加稳定。
[Abstract]:Compared with the traditional coarse-crystal material, the bulk ultra-fine crystal (UFG) material has become one of the hot spots in the current material field due to its excellent mechanical properties and physical properties. The strong plastic deformation (SPD) is one of the most common methods for preparing the ultra-fine crystal material of the present block due to its good grain refining ability. In recent years, some low-temperature strong plastic deformation techniques such as low-temperature rolling, low-temperature multi-way forging, low-temperature high-pressure torsion, low-temperature equal-channel corner extrusion and the like are successfully applied to the preparation of bulk superfine crystal materials. Compared with the high-temperature and strong plastic deformation, the low-temperature can effectively inhibit the dynamic recovery process, promote the effective accumulation of the internal dislocation of the material, and induce the generation of the mechanical columnar crystal, thereby improving the grain refining efficiency, and obtaining the superfine crystal tissue at a lower corresponding variable. The low-temperature and large-load impact deformation is a potential new method for preparing the bulk ultra-fine crystal material. Compared with the common strong plastic deformation method, the method has the advantages of simple process, no need of special equipment, and is expected to prepare the bulk superfine crystal material with large size and has good industrial application prospect. However, the research on the preparation of bulk ultra-fine crystal material with low-temperature and large-load impact deformation is very limited. Therefore, the microstructure evolution and performance of the bulk metallic material of the system under the impact of low temperature and large load are of great significance. In this paper, gold phase analysis, TEM, XRD and microhardness were used. The microstructure and corrosion properties of pure copper with FCC structure and the industrial pure iron with BCC structure and the effect of subsequent annealing on the microstructure and properties of the microstructure were studied by means of polarization curve and other characterization methods. The main research results are as follows: (1) the experiment of low-temperature and large-load impact deformation of pure copper is carried out, and the bulk ultra-fine crystal pure copper material with the plate-like structure is successfully prepared. When the variable is 2.21, the grain is equiaxed from the cross-section, the size is 150-450 nm, and the width is 30-220nm from the longitudinal section. The microstructure of pure copper shows that the grain refinement is the result of the synergistic effect of the dislocation cell evolution mechanism, the dynamic recrystallization mechanism and the crystal grain refining mechanism. (2) After annealing for 60min at 190.degree. C., the recrystallization of the pure copper occurs, the high-density dislocation disappears, the grain boundary is clear and straight, the crystal grains are still equiaxed in the cross section, the size is changed to 200-450 nm, the longitudinal section is still a strip-shaped, the width is 70-100nm, and a large amount of the annealed nanocrystalline is also observed on the longitudinal section, and the width of the columnar crystal is 10-100 nm; and (3) after the low-temperature large-load impact, The corrosion rate of pure copper in 0.5M NaCl solution is reduced; after annealing for 60 min at 190.degree. C., the corrosion rate of the sample is further reduced; and (4) industrial pure iron low-temperature large-load impact deformation experiment is carried out, and the bulk ultra-fine crystal industrial pure iron material with the plate-like structure is successfully prepared. When the variable is 2.21, the grain is equiaxed from the cross-section, the size is 100-300nm, and the width is 100-350nm from the longitudinal section. The micro-structure research shows that the grain refinement of the low-temperature and large-load impact of the industrial pure iron is mainly accomplished by the synergistic effect of the grain breaking mechanism and the dislocation cell refining mechanism. In addition, the presence of the cementite has a certain catalytic effect on the grain refinement of the industrial pure iron; (5) after annealing at 500 DEG C for 60 minutes, the dislocation density of the industrial pure iron is obviously reduced, the grain outline is clear, and the grains are still equiaxed in the cross section, and the size thereof is 120-310nm; the longitudinal section is still strip-shaped, and the width thereof is 80-350nm. and after the low-temperature and large-load impact, the corrosion rate of the industrial pure iron in the solution of 0.5 M NaCl is reduced, the passivation current is reduced, the passivation interval is widened, and the passivation capacity is obviously improved; After annealing at 500 鈩，
本文编号：2319749
[Abstract]:Compared with the traditional coarse-crystal material, the bulk ultra-fine crystal (UFG) material has become one of the hot spots in the current material field due to its excellent mechanical properties and physical properties. The strong plastic deformation (SPD) is one of the most common methods for preparing the ultra-fine crystal material of the present block due to its good grain refining ability. In recent years, some low-temperature strong plastic deformation techniques such as low-temperature rolling, low-temperature multi-way forging, low-temperature high-pressure torsion, low-temperature equal-channel corner extrusion and the like are successfully applied to the preparation of bulk superfine crystal materials. Compared with the high-temperature and strong plastic deformation, the low-temperature can effectively inhibit the dynamic recovery process, promote the effective accumulation of the internal dislocation of the material, and induce the generation of the mechanical columnar crystal, thereby improving the grain refining efficiency, and obtaining the superfine crystal tissue at a lower corresponding variable. The low-temperature and large-load impact deformation is a potential new method for preparing the bulk ultra-fine crystal material. Compared with the common strong plastic deformation method, the method has the advantages of simple process, no need of special equipment, and is expected to prepare the bulk superfine crystal material with large size and has good industrial application prospect. However, the research on the preparation of bulk ultra-fine crystal material with low-temperature and large-load impact deformation is very limited. Therefore, the microstructure evolution and performance of the bulk metallic material of the system under the impact of low temperature and large load are of great significance. In this paper, gold phase analysis, TEM, XRD and microhardness were used. The microstructure and corrosion properties of pure copper with FCC structure and the industrial pure iron with BCC structure and the effect of subsequent annealing on the microstructure and properties of the microstructure were studied by means of polarization curve and other characterization methods. The main research results are as follows: (1) the experiment of low-temperature and large-load impact deformation of pure copper is carried out, and the bulk ultra-fine crystal pure copper material with the plate-like structure is successfully prepared. When the variable is 2.21, the grain is equiaxed from the cross-section, the size is 150-450 nm, and the width is 30-220nm from the longitudinal section. The microstructure of pure copper shows that the grain refinement is the result of the synergistic effect of the dislocation cell evolution mechanism, the dynamic recrystallization mechanism and the crystal grain refining mechanism. (2) After annealing for 60min at 190.degree. C., the recrystallization of the pure copper occurs, the high-density dislocation disappears, the grain boundary is clear and straight, the crystal grains are still equiaxed in the cross section, the size is changed to 200-450 nm, the longitudinal section is still a strip-shaped, the width is 70-100nm, and a large amount of the annealed nanocrystalline is also observed on the longitudinal section, and the width of the columnar crystal is 10-100 nm; and (3) after the low-temperature large-load impact, The corrosion rate of pure copper in 0.5M NaCl solution is reduced; after annealing for 60 min at 190.degree. C., the corrosion rate of the sample is further reduced; and (4) industrial pure iron low-temperature large-load impact deformation experiment is carried out, and the bulk ultra-fine crystal industrial pure iron material with the plate-like structure is successfully prepared. When the variable is 2.21, the grain is equiaxed from the cross-section, the size is 100-300nm, and the width is 100-350nm from the longitudinal section. The micro-structure research shows that the grain refinement of the low-temperature and large-load impact of the industrial pure iron is mainly accomplished by the synergistic effect of the grain breaking mechanism and the dislocation cell refining mechanism. In addition, the presence of the cementite has a certain catalytic effect on the grain refinement of the industrial pure iron; (5) after annealing at 500 DEG C for 60 minutes, the dislocation density of the industrial pure iron is obviously reduced, the grain outline is clear, and the grains are still equiaxed in the cross section, and the size thereof is 120-310nm; the longitudinal section is still strip-shaped, and the width thereof is 80-350nm. and after the low-temperature and large-load impact, the corrosion rate of the industrial pure iron in the solution of 0.5 M NaCl is reduced, the passivation current is reduced, the passivation interval is widened, and the passivation capacity is obviously improved; After annealing at 500 鈩，
本文编号：2319749
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