时效对AZ63镁合金稀土镧-铈转化膜耐孔蚀性能的影响

时效时间对镁合金表面稀土转化膜的耐腐蚀性能有很大影响.将AZ63镁合金浸入硝酸镧和硝酸铈混合溶液中,在其表面制备稀土镧-铈转化膜并在空气中作0,24,48,60,72,90 h时效处理.利用循环伏安曲线、极化曲线、扫描电镜对AZ63镁合金稀土镧-铈转化膜在3％NaCl溶液中的孔蚀行为进行了研究.结果表明:时效处理能进一步提高稀土镧-铈转化膜的附着力、致密性和均匀性,从而显著提高镁合金的耐蚀性;稀土镧-铈转化膜的耐蚀性随时效时间的增加先增强后减弱,时效48 h时稀土镧-铈转化膜致密、附着力强,具有较好的耐蚀性,不易发生孔蚀,击穿电位为-1.418 V,孔蚀坑较浅;大电流密度更容易诱发孔蚀,当诱导孔蚀电流密度分别为0.4,1.5 mA/cm2时,时效48 h稀土镧-铈转化膜的诱发孔蚀时间为480,300 s.     

稀土镁合金的研究现状

本文综述了稀土对镁合金组织、力学性能、耐腐蚀性能及耐热性能的影响，概括了稀土镁合金的发展进程，对稀土镁合金的研究开发、应用前景进行了展望。     

镁合金双稀土转化膜及其耐蚀性能的研究

已有的铬酸盐转化膜技术因污染环境而被限制使用.采用硝酸铈和硝酸镧混合溶液对AZ31镁合金进行了双稀土转化处理,讨论了浸渍时间对转化膜耐腐蚀性能的影响.采用点滴试验、盐水浸溃试验和Tafel极化法评价了双稀土转化膜的耐腐蚀性能.结果表明,经过双稀土处理后,镁舍金的变色时间由6s提高到79 s;在3.5%NaCl溶液中转化膜的腐蚀速率是基体的1/5;转化膜的腐蚀电位提高了0.313 V,腐蚀电流密度由4.03×10-2 mA/cm2降为2.31×10-4 mA/cm2;双稀土转化膜的微观形貌呈破裂的干泥状;双稀土转化处理提高了镁合金的耐蚀性能,随处理时间的延长耐蚀性呈先增加后降低的趋势.     

稀土金属在铸造镁合金中的应用

叙述了稀土金属在铸造镁合金中应用的发展过程和稀土铸造镁合金的最新进展，概述了稀土金属对镁合金的强化、铸造工艺性的改善和耐腐蚀性能的提高等方面的作用机理。     

合金元素对镁合金耐腐蚀性能影响的研究进展

添加合金元素即合金化是改善镁合金性质、性能的有效途径。总结了基础合金元素(Al、Zn、Mn、Zr等)和微量合金元素(Ce、La、Sc、Er、Nd、Y、Sm、Ho、Gd及混合稀土等稀土元素和Ca、Sr等碱土金属元素以及Pb、Sn、Sb、Si、Hg、Ga等)对合金化镁合金耐腐蚀性能的影响,评述了失重法、电化学方法等合金化镁合金耐腐蚀性能的主要研究方法,指出了当前镁合金合金化及耐腐蚀性能研究中存在的问题和发展方向。     

ZM5镁合金表面微弧火花La合金化研究

为了研究纯稀土对镁合金腐蚀性能的影响,用高能微弧火花合金化(电火花)设备在ZM5镁合金上进行了La合金化.使用金相、电子探针和X射线衍射仪等设备对获得的涂层进行了显微结构和成分分析.并利用电化学测试仪器进行了极化曲线的测试.研究表明,可获得无气孔、裂纹的冶金结合的界面和合金化层,成分分布存在一个渐变的过程.合金化层主要由稀土镧、AlLa2与Mg17Al12相组成;合金化层的腐蚀电位正移了大约59 mV,而合金化层在3.5%NaCl溶液中的耐腐蚀性能几乎没有改善.     

稀土在镁合金中作用的研究现状

稀土元素在镁合金中具有阻燃、净化熔体等作用,能有效改善合金的铸造性能;可细化显微组织、形成准晶相、抑制形变织构,提高镁合金的室温及高温强度和塑韧性等力学性能;并改变镁合金表面腐蚀层结构、控制阴极相数量和分布以及影响电化学过程,从而改善镁合金的耐腐蚀性能。总结了利用稀土元素改善镁合金组织性能的研究现状,并对稀土镁合金的发展前景进行了展望。     

镁合金健身器材的表面转化膜制备与性能研究北大核心CSCD

采用正交试验法对AZ91镁合金表面(La+Ce)双稀土转化膜进行了磷酸盐致密化工艺优化,并对比分析了基材和稀土转化膜致密化前后的耐腐蚀性能。结果表明,致密化工艺参数中对转化膜耐腐蚀性能的影响从大至小的顺序为:致密化温度>致密化时间>(NH4)3PO4浓度,正交极差分析结果优化得到的AZ91镁合金的最佳稀土转化膜致密化工艺为致密化温度45℃、致密化时为3min和(NH4)3PO4浓度6%;磷酸盐致密化处理后可在稀土转化膜表面形成CePO4、Mg3(PO4)2和LaPO4相,并对致密化处理前的(La+Ce)双稀土转化膜表面的裂纹/孔洞缺陷进行填补和修复;析氢腐蚀、电化学阻抗谱和极化曲线测试结果相吻合,即3种试样的耐腐蚀性能从高至低顺序为:致密化后的试样>致密化前的试样>空白试样,即(La+Ce)双稀土转化膜可以对AZ91镁合金起到保护作用,且经过磷酸盐致密化处理后试样的耐腐蚀性能会进一步提高。     

稀土在镁合金中作用的研究现状

稀土元素在镁合金中具有阻燃、净化熔体等作用，能有效改善合金的铸造性能；可细化显微组织、形成准晶相、抑制形变织构，提高镁合金的室温及高温强度和塑韧性等力学性能；并改变镁合金表面腐蚀层结构、控制阴极相数量和分布以及影响电化学过程，从而改善镁合金的耐腐蚀性能。总结了利用稀土元素改善镁合金组织性能的研究现状，并对稀土镁合金的发...     

镁合金健身器材的表面转化膜制备与性能研究

采用正交试验法对AZ91镁合金表面(La+Ce)双稀土转化膜进行了磷酸盐致密化工艺优化,并对比分析了基材和稀土转化膜致密化前后的耐腐蚀性能。结果表明,致密化工艺参数中对转化膜耐腐蚀性能的影响从大至小的顺序为:致密化温度致密化时间(NH_4)_3PO_4浓度,正交极差分析结果优化得到的AZ91镁合金的最佳稀土转化膜致密化工艺为致密化温度45℃、致密化时为3min和(NH_4)_3PO_4浓度6%;磷酸盐致密化处理后可在稀土转化膜表面形成CePO_4、Mg_3(PO_4)_2和LaPO_4相,并对致密化处理前的(La+Ce)双稀土转化膜表面的裂纹/孔洞缺陷进行填补和修复;析氢腐蚀、电化学阻抗谱和极化曲线测试结果相吻合,即3种试样的耐腐蚀性能从高至低顺序为:致密化后的试样致密化前的试样空白试样,即(La+Ce)双稀土转化膜可以对AZ91镁合金起到保护作用,且经过磷酸盐致密化处理后试样的耐腐蚀性能会进一步提高。     

事故容错燃料包壳候选材料的研究现状及展望

2011年福岛核电站事故中,反应堆堆芯燃料中的锆合金包壳在事故工况下与高温水蒸汽发生剧烈氧化反应继而产生大量的氢气和热量,最终导致反应堆堆芯熔化和氢气爆炸,对社会和环境造成极大负面影响。自此之后,国内外纷纷展开对事故容错燃料的研究开发。相较于传统的UO2-Zr合金燃料体系,事故容错燃料能够在反应堆正常运行工况下维持或提高燃料性能,并在事故发生后相当长的一段时间内维持堆芯完整性,提供足够的时间裕量来采取事故应对措施。反应堆堆芯环境非常极端,包壳长期处于高温高压腐蚀介质中,同时还受到中子辐照的影响,因此新型包壳材料需要较好的耐腐蚀性和辐照稳定性。经不同研究者的研究评估,目前能够替代Zr合金的事故容错燃料包壳材料可分为陶瓷材料和金属材料两类:陶瓷材料主要以SiC/SiC复合材料为代表;金属材料主要有以FeCrAl为代表的Fe基合金和以Mo为代表的难熔金属及其合金。上述三种替代Zr包壳的材料各有其利弊,均未达到工程应用水平,并且都存在待解决的关键性问题。其中,FeCrAl合金的研发进展最快,目前在热学性能、力学性能、抗腐蚀性能、抗辐照性能等方面表现较好,但在工业加工和焊接等方面仍有待进一步改善。就SiC/SiC复合材料而言,由于SiC自身的高脆性而导致力学强度不足,不同的研究者提出了不同的结构设计思路试图降低包壳管失效概率,但包壳最终的结构设计仍未确定,而辐照引起的热导率急剧降低及连接密封和加工制造等方面还在不断研究中。Mo及Mo合金的力学性能和抗辐照性能较好,但自身抗腐蚀性较差,解决思路主要集中在提高钼纯度、调整合金的元素成分、进行表面涂层等方面。目前,对后两种材料包壳管的加工能力均未达到薄壁长管的工业制造水平。对于这几种候选包壳材料,需要建立属性数据库和一套完善的标准来衡量材料的质量。此外,还需开发相应的程序来评估包壳在堆内的行为。本文主要综述了SiC/SiC复合材料、FeCrAl合金、Mo及Mo合金三种候选包壳材料的研究进展,包括候选包壳材料的物理性质、耐腐蚀性能、力学性能、抗辐照性能、芯块-包壳力学与化学相互作用、在事故工况下的行为和工程应用等,综合分析了事故容错燃料包壳材料当前的研究现状,指出了各事故容错燃料包壳未来需集中解决的关键性问题。     

容错事故燃料包壳用FeCrAl合金的研究进展EI北大核心CSCD

福岛事故后,人们迫切需要开发相应的燃料包壳材料以忍受严重事故发生时的极端工况,从而提高核电站的事故承受能力。尽管FeCrAl合金的宏观中子吸收截面要远远高于锆合金,但其在严重事故下良好的耐腐蚀性、优越的高温力学性能及抗辐照损伤能力,使其被列为事故容错燃料包壳的候选材料之一。然而,现有FeCrAl合金难以满足核电站用材料的要求,因此需对其进行优化,以获得更佳的性能。本文系统总结了近年来关于优化后FeCrAl合金的腐蚀行为、力学性能、辐照后的微观结构及力学性能变化、焊接性及加工性等方面的研究进展,分析了FeCrAl合金的高温腐蚀机理以及引起FeCrAl合金微观结构及力学性能变化的主要原因,提出了FeCrAl合金在高温腐蚀、焊接性以及加工性等过程中存在的主要问题以及未来的研究方向。     

Anelastic spectroscopy in Ti-13V-11Cr-3Al alloy

Titanium alloys display low density, high mechanical strength and good corrosion resistance, being ideal structural materials for aerospace engineering. In this paper, the effects of nitrogen on the anelastic properties of the bcc alloy Ti-13V-11Cr-3Al were investigated. The results show an asymmetric thermally activated relaxation structure in the high-temperature region. This relaxation structure was decomposed, and relaxation processes due to stress-induced ordering of nitrogen atoms around the metallic matrix and substitutional solutes were identified.     

高熵合金力学性能的研究进展

高熵合金作为一类新型的合金,具有许多优于传统合金的性能,在诸多领域有广阔的应用前景。高熵合金现阶段的研究主要集中在其力学性能方面,它的高强度、高硬度、高耐磨性和耐腐蚀性等优点展现出了其作为在严酷条件下服役的结构材料的潜力,但目前对高熵合金的研究仍处于探索性阶段,所以研究高熵合金的力学性能具有重要的现实意义。主要综述了组分、制备工艺、热处理工艺、冷轧等对高熵合金的组织与力学性能的影响,并展望了高熵合金的应用前景。     

Effect of molybdenum on SCC of 17-4PH stainless steel under different aging conditions in chloride solutions

Type 17-4 PH martensitic precipitation-hardenable stainless steel, having a combination of high mechanical properties and good corrosion resistance is widely used in aerospace, chemical, and petrochemical and food industries This alloy has a high resistance to stress corrosion cracking but age hardening treatment, increases its sensitivity to stress corrosion cracking. There are several works investigating the influence of different aging treatments on the microstructure, mechanical properties and corrosion resistance of 17-4 PH steels, however there are little works studying the simultaneous effects of aging treatments and molybdenum content on corrosion properties of these steels. In this research, the effect of molybdenum on stress corrosion cracking resistance of 17-4 PH alloy using U-bend samples in chloride solutions, as well as its effect on passivity, has been investigated. Quantometer, Scanning Electron Microscope(SEM) and potentiostat were used to determine the chemical composition, microstructure and anodic polarization behavior of the alloys. It is found that molybdenum has a useful effect on stress corrosion cracking resistance under the peak aged conditions, and this is because of development of delta-ferrite phase by increasing the molybdenum content and subsequently decreasing the strength of the alloy.     

Dendritic Microstructure Affecting Mechanical Properties and Corrosion Resistance of an Al-9 wt% Si Alloy

It has been reported that the mechanical properties and corrosion resistance of metallic alloys depend strongly on the solidification microstructural arrangement. The correlation of corrosion behavior and mechanical properties with microstructure parameters can be very useful for planning solidification conditions in order to achieve desired final properties. The aim of the present work is to investigate the influence of dendritic microstructural parameters of an Al-9 wt.% Si alloy on mechanical properties and corrosion resistance. The experimental results establish correlations between secondary dendrite arm spacings (λ₂) and ultimate tensile strength (σ_u), yield strength (σ_y), corrosion potential (E_Corr), and corrosion rate (i_Corr).     

High temperature characteristics of Ir–Ta coated and aluminized Ni-base single crystal superalloys

High temperature oxidation and hot corrosion properties of Ir–Ta coated and aluminized Ni-base superalloys are presented. An Ir–Ta binary alloy, proposed as a novel metallic bond coat material, was coated on a Ni-base single crystal superalloy TMS-75 using electron beam physical vapor deposition, followed by a conventional low activity Al pack cementation process. Cyclic oxidation tests and hot corrosion tests revealed that these Ir–Ta coated and aluminized specimens showed reasonably good oxidation and hot corrosion resistance. In addition, it was found that the formation of TCP phases is suppressed by the presence of the Ir–Ta enriched layer. These results indicated that the Ir–Ta alloy system is promising as a new metallic bond coat material for high temperature structural materials.     

A review of selective laser melting of aluminum alloys: Processing,microstructure, property and developing trends

Selective laser melting (SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most pervasive structural materials, is well known for high specific strength and good corrosion resistance. But the poor laser formability of aluminum alloy restricts its application. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing aluminum alloys. Some efforts have been made to solve the above problems. This paper discusses the current research status both related to the scientific understanding and technology applications. The paper begins with a brief introduction of basic concepts of aluminum alloys and technology characterization of laser selective melting. In addition, solidification theory of SLM process and formation mechanism of metallurgical defects are discussed. Then, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively. Lastly, a future outlook is given at the end of this review paper.     

A novel biomedical titanium alloy with high antibacterial property and low elastic modulus

β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend the lifetime of prosthetics.However,other issues,such as the infection or inflammation postimplantation,still trouble the titanium alloy's clinical application.In this paper,we developed a novel near β-titanium alloy (Ti-13Nb-13Zr-13Ag,TNZA) with low elastic modulus and strong antibacterial ability by the addition of Ag element followed by proper microstructure controlling,which could reduce the stress shielding and bacterial infections simultaneously.The microstructure,mechanical properties,corrosion resistance,antibacterial properties and cell toxicity were studied using SEM,electrochemical testing,mechanical test and cell tests.The results have demonstrated that TNZA alloy exhibited an elastic modulus of 75-87 GPa and a strong antibacterial ability (up to 98 ％ reduction) and good biocompatibility.Moreover,it was also shown that this alloy's corrosion resistance was better than that of Ti-13Nb-13Zr.All the results suggested that Ti-13Nb-13Zr-13Ag might be a competitive biomedical titanium alloy.     

High temperature characteristics of Ir–Ta coated and aluminized Ni-base single crystal superalloys

High temperature oxidation and hot corrosion properties of Ir–Ta coated and aluminized Ni-base superalloys are presented. An Ir–Ta binary alloy, proposed as a novel metallic bond coat material, was coated on a Ni-base single crystal superalloy TMS-75 using electron beam physical vapor deposition, followed by a conventional low activity Al pack cementation process. Cyclic oxidation tests and hot corrosion tests revealed that these Ir–Ta coated and aluminized specimens showed reasonably good oxidation and hot corrosion resistance. In addition, it was found that the formation of TCP phases is suppressed by the presence of the Ir–Ta enriched layer. These results indicated that the Ir–Ta alloy system is promising as a new metallic bond coat material for high temperature structural materials.