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AZ31镁合金在海洋大气环境中的腐蚀行为 总被引:2,自引:0,他引:2
通过室外大气暴露试验,研究了AZ31镁合金在万宁和青岛2个海洋大气环境试验站点1~5年的腐蚀规律,用失重法测定了腐蚀速率,并用SEM和XRD分析了5年后表面腐蚀形貌和腐蚀产物的组成。研究表明,AZ31镁合金暴露在海洋大气环境5年后的腐蚀动力学符合幂函数规律,万宁站的腐蚀速率高于青岛站,且腐蚀速率都随暴露时间的延长而降低,但青岛站腐蚀速率降低幅度更大,腐蚀产物膜对基体保护作用较万宁站强;AZ31镁合金暴露在万宁站和青岛站5年后的腐蚀速率分别为37.6和13.5μm·a-1,腐蚀产物以MgCl2,MgCO3,MgSO3,MgSO4,Mg5(CO3)4(OH)2·8H2O和Mg2(OH)3Cl·4H2O为主;AZ31镁合金在海洋大气环境中不耐腐蚀,表面布满点蚀坑,相对湿度对镁合金较长周期的腐蚀有显著影响。 相似文献
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磁场作用下合金元素在AZ31镁合金中的分布 总被引:8,自引:0,他引:8
研究了镁合金AZ31分别在无磁场及磁场作用条件下凝固的微观结构及合金元素的分布;对凝固过程中磁场的分布进行了数值模拟。结果表明,与无磁场处理凝固的镁合金组织比较,镁合金AZ31的凝固过程在磁场作用条件下合金元素在晶界上和晶内的分布有较大的变化,在较强静磁场作用下聚集在晶界上的共晶体组织明显减少,共晶组织形成的网络变得不连续,同时在晶内和晶界附近出现了大量近似球状的共晶质点,提高了合金元素在晶内的固溶度,有利于改善镁合金的综合性能。 相似文献
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B. S. Naik D. L. Chen X. Cao P. Wanjara 《Metallurgical and Materials Transactions A》2014,45(10):4333-4349
The present study was aimed at characterizing the microstructure, texture, hardness, and tensile properties of an AZ31B-H24 Mg alloy that was friction stir lap welded (FSLWed) at varying tool rotational rates and welding speeds. Friction stir lap welding (FSLW) resulted in the presence of recrystallized grains and an associated hardness drop in the stir zone (SZ). Microstructural investigation showed that both the AZ31B-H24 Mg base metal (BM) and SZ contained β-Mg17Al12 and Al8Mn5 second phase particles. The AZ31B-H24 BM contained a type of basal texture (0001)〈11 \( \overline{2} \) 0〉 with the (0001) plane nearly parallel to the rolled sheet surface and 〈11 \( \overline{2} \) 0〉 directions aligned in the rolling direction. FSLW resulted in the formation of another type of basal texture (0001)〈10 \( \overline{1} \) 0〉 in the SZ, where the basal planes (0001) became slightly tilted toward the transverse direction, and the prismatic planes (10 \( \overline{1} \) 0) and pyramidal planes (10 \( \overline{1} \) 1) exhibited a 30 deg + (n ? 1) × 60 deg rotation (n = 1, 2, 3, …) with respect to the rolled sheet normal direction, due to the shear plastic flow near the pin surface that occurred from the intense local stirring. With increasing tool rotational rate and decreasing welding speed, the maximum intensity of the basal poles (0001) in the SZ decreased due to a higher degree of dynamic recrystallization that led to a weaker or more random texture. The tool rotational rate and welding speed had a strong effect on the failure load of FSLWed joints. A combination of relatively high welding speed (20 mm/s) and low tool rotational rate (1000 rpm) was observed to be capable of achieving a high failure load. This was attributed to the relatively small recrystallized grains and high intensity of the basal poles in the SZ arising from the low heat input as well as the presence of a small hooking defect. 相似文献
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Liang Wu Grigoreta M. Stoica Hao-Hsiang Liao Sean R. Agnew E. Andrew Payzant Gongyao Wang Douglas E. Fielden Lijia Chen Peter K. Liaw 《Metallurgical and Materials Transactions A》2007,38(13):2283-2289
The fatigue behavior of magnesium-alloy, AZ31B, prestrained by equal-channel-angular pressing (ECAP) was studied as a function
of the accumulated plastic-strain level and the orientation of the samples (along and perpendicular to the ECAP pressing direction).
The material was processed via route B
C
, at 200 °C, for 1, 2, and 8 passes, with and without a back pressure (BP) applied on the billet during ECAP. The low-cycle
fatigue behavior of the AZ31B alloy is shown to be anisotropic and texture dependent. Due to the initial texture orientation,
the specimens loaded parallel to the ECAP pressing direction have a longer fatigue life than the samples loaded perpendicular
to it. The low-cycle fatigue life of the AZ31B alloy is enhanced by ECAP. The fatigue-property improvement is discussed in
light of the grain-size refinement, enhanced ductility, and texture evolution.
This article is based on a presentation given in the symposium entitled “Deformation and Fracture from Nano to Macro: A Symposium
Honoring W.W. Gerberich’s 70th Birthday,” which occurred during the TMS Annual Meeting, March 12–16, 2006 in San Antonio,
Texas and was sponsored by the Mechanical Behavior of Materials and Nanomechanical Behavior Committees of TMS. 相似文献
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Michal Gzyl Andrzej Rosochowski Raphael Pesci Lech Olejnik Evgenia Yakushina Paul Wood 《Metallurgical and Materials Transactions A》2014,45(3):1609-1620
Incremental equal channel angular pressing (I-ECAP) is a severe plastic deformation process used to refine grain size of metals, which allows processing very long billets. As described in the current article, an AZ31B magnesium alloy was processed for the first time by three different routes of I-ECAP, namely, A, BC, and C, at 523 K (250 °C). The structure of the material was homogenized and refined to ~5 microns of the average grain size, irrespective of the route used. Mechanical properties of the I-ECAPed samples in tension and compression were investigated. Strong influence of the processing route on yield and fracture behavior of the material was established. It was found that texture controls the mechanical properties of AZ31B magnesium alloy subjected to I-ECAP. SEM and OM techniques were used to obtain microstructural images of the I-ECAPed samples subjected to tension and compression. Increased ductility after I-ECAP was attributed to twinning suppression and facilitation of slip on basal plane. Shear bands were revealed in the samples processed by I-ECAP and subjected to tension. Tension–compression yield stress asymmetry in the samples tested along extrusion direction was suppressed in the material processed by routes BC and C. This effect was attributed to textural development and microstructural homogenization. Twinning activities in fine- and coarse-grained samples have also been studied. 相似文献
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M. Gao Z. M. Wang X. Y. Li X. Y. Zeng 《Metallurgical and Materials Transactions A》2012,43(1):163-172
Laser keyhole welding of Ti-6Al-4V titanium alloy to AZ31B magnesium alloy was developed, and the correlations of process
parameters, joint properties, and bonding mechanism were studied. The results show that the offset from the laser beam center
on AZ31B side to the edge of the weld seam plays a big role in the joint properties by changing the power density irradiated
at the Ti–Mg initial interface. The optimal range of the offset is 0.3 to 0.4mm in the present study. Some lamellar and granular
Ti-rich mixtures are observed in the fusion zone, which is formed by intermixing melted Ti-6Al-4V with liquid AZ31B. The maximum
ultimate tensile strength of the joints reaches 266 MPa. Furthermore, the fracture surface consists of scraggly remaining
weld metal and smooth Ti surface. The higher the failure strength, the smaller the proportion of smooth Ti surface to whole
interface is. Finally, the bonding mechanism of the interfacial layer is summarized by the morphologies and test results of
fracture surfaces. 相似文献
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Wrought magnesium alloys are interesting materials for automotive and aeronautical industries due to their low density in comparison to steel and aluminium alloys, making them ideal candidates when designing a lower weight vehicle. However, due to their hexagonal close‐packed (hcp) crystal structure, magnesium alloys exhibit low formability at room temperature. For that reason, in this study a high velocity forming process, electromagnetic forming (EMF), was used to study the formability of AZ31B magnesium alloy sheet at high strain rates. In the first stage of this work, specimens of AZ31B magnesium alloy sheet have been characterised by uniaxial tensile tests at quasi‐static and dynamic strain rates at room temperature. The influence of the strain rate is outlined and the parameters of Johnson‐Cook constitutive material model were fit to experimental results. In the second stage, sheets of AZ31B magnesium alloy have been biaxially deformed by electromagnetic forming process using different coil and die configurations. Deformation values measured from electromagnetically formed parts are compared to the ones achieved by conventional forming technologies. Finally, numerical study using an alternative method for computing the electromagnetic fields in the EMF process simulation, a combination of Finite Element Method (FEM) for conductor parts and Boundary Element Method (BEM) for insulators, is shown. 相似文献
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采用等离子喷涂方法在AZ31B镁合金表面制备Al_2O_3、Al_2O_3-13%TiO2(AT13)和Al_2O_3-20%TiO_2(AT20)三种陶瓷涂层;对比研究陶瓷层的微观组织结构、孔隙率、结合强度及电化学腐蚀性能。结果表明:等离子喷涂的陶瓷涂层具有典型的层状结构,涂层具有良好的结合强度和较低的孔隙率。随着TiO2加入量的增多,陶瓷涂层的结合强度升高,孔隙率降低,耐蚀性提高;AT20涂层与镁合金基体相比自腐蚀电位升高了701mV,自腐蚀电流密度降低了两个数量级,阻抗是基体的6倍,AT20涂层的耐蚀性最优。陶瓷涂层的电化学腐蚀过程表现为膜层局部腐蚀和基体腐蚀并造成涂层层状剥离。 相似文献
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Liu Shengfa Liu Linyan Huang Shangyu Xu Ping Wang Zhongfan 《中国稀土学报(英文版)》2006,24(2):247-247
Effect of cerium addition on corrosion resistance of AZ91 magnesium alloy was investigated using the static weight loss and polarization curve method as well as metallographical observation. The results indicate that a small amount of cerium (0.2% - 0.8%) in AZ91 magnesium alloy can significantly reduce the corrosion rate, enhance the electrode voltage and lower corrosion current density in 3.5%NaCl aqueous solution, and AZ91-0.8% Ce alloy has better corrosion resistant performance. The reason for increasing corrosion resistance is attributed to the addition of Ce, refining the α-Mg grain, reducing the segregation of element Al, and improving the morphologies of β-Mg17 Al12 phases. 相似文献
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采用卧式挤压机,对AZ31镁合金型材挤压工艺进行了生产跟踪试验研究,确定了AZ31镁合金型材在挤压操作时的最佳挤压筒温度、镁棒温度、模具预热温度和挤压速度。分析了型材产品的力学性能和微观组织结构,结果表明在给定操作工艺下,可得到高强度、细晶粒度、良好塑性和表面光洁的挤压型材。 相似文献
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J. Yang D. R. Ni D. Wang B. L. Xiao Z. Y. Ma 《Metallurgical and Materials Transactions A》2014,45(4):2101-2115
Strain-controlled low-cycle fatigue (LCF) behavior of friction stir-welded (FSW) AZ31 joints, produced at rotation rates of 800 and 3500 rpm, was studied. The joints exhibited symmetric hysteresis loops, whereas asymmetric loops were observed for the parent material (PM). The fatigue resistance of the FSW joints was slightly improved as the rotation rate increased, and both the FSW joints possessed a fatigue life similar to that of the PM at the low strain amplitude of 0.1 pct. The obtained fatigue data for the PM and FSW joints can be well described using the Coffin–Manson and Basquin’s relationships. For the FSW joints, during LCF deformation, the $ \left\{ {10\bar{1}2} \right\} $ twinning originated from the nugget zone (NZ)/thermomechanically affected zone (TMAZ) boundary and then propagated to the NZ interior. This was attributed to different textures in these regions: the center of the NZ exhibited a hard orientation, whereas a soft orientation was observed in the region around the NZ/TMAZ boundary. The fatigue cracks initiated at the bottom of the joints and propagated along the NZ/TMAZ boundary or the NZ adjacent to the NZ/TMAZ boundary. 相似文献
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Hideki Yamagishi Mikio Fukuhara Hiroaki Matsumoto Akihiko Chiba 《Metallurgical and Materials Transactions A》2010,41(8):2151-2161
Nondestructive evaluation of cyclic-tension fatigue in a rolled magnesium alloy, Mg-3Al-1Zn, was performed using vertically
polarized shear wave (SV) reflection and shear horizontal wave (SH) transmission methods. Internal friction measured by SV
reflection increased rapidly in the early stages of the fatigue and finally saturated, showing dominating interactions of
movable dislocations and twinning boundaries with the waves as acoustic nonlinearities. The propagation time and logarithmic
damping ratio in the SH transmission method followed a repeated increase and subsequent sudden decrease pattern, and finally
converged toward fatigue failure due to acoustoelasticity, which represents the interaction with residual stresses. The wave
and phase data were determined using an optical microscope, a scanning electron microscope, a surface roughness tester, and
X-ray diffraction. The results demonstrated that during the fatigue process, residual stress accumulated on the compressive
side of the specimen, despite the applied cyclic-tension loading. Brittle cracks that originated in inclusions provided sudden
relief from the residual stress. 相似文献