Formation mechanism of pulse current anodized film on AZ91D Mg alloy

The kinetics of forming process of pulse current anodized film on AZ91D Mg alloy was studied by the voltage-time and thickness-time curves. The surface morphology, structure, elemental constitution and valences of the anodic films were analyzed by SEM, EDS, XPS and XRD respectively. The results show that the film-forming process can be divided into four stages. Formation of a dense layer before sparking is the first stage. Formation of a porous layer accompanied with slight sparking is the second stage. The third stage is characterized by fast growth of the porous layer accompanied with more intensive sparking. The fourth stage starts after the sparking process becomes even more vigorous and the pores become large.     

Enrichment of alloying elements in anodized magnesium alloys

The possibility of enrichment of alloying elements in magnesium alloys as a consequence of growth of an anodic film has been investigated for sputtering-deposited Mg-0.4 at.% W and Mg-1.0 at.% W alloys. The alloys were anodized at 10 mA cm⁻² to various voltages, up to 150 V, in 3 M ammonium hydroxide/0.05 M ammonium phosphate electrolyte at 293 K. The alloys revealed enrichments of tungsten to at least 1.7×10¹⁵ and 2.9×10¹⁵ W atoms cm⁻² for the Mg-0.4 at.% W and Mg-1.0 at.% W alloys respectively. The enrichment behaviour appears to be similar to that in dilute aluminium alloys, which occurs for alloying elements with oxides having Gibbs free energies per equivalent for formation exceeding that for formation of alumina.     

Micromechanical properties of Co-W alloys electrodeposited under pulse conditions

Results of the investigation of pulse current frequency influence (rectangular unipolar pulses, i _m = 3 A/dm², relative pulse duration 3, frequency 0.67–333 Hz, Q = 3600 C/dm²) on the properties of Co-W alloys at electrochemical deposition—deposition rate, current efficiency, structure of obtained coatings, and their microhardness (microindentation and sclerometric ones)—are presented. The correlation between the microhardness determined by quasi-static indentation and the “organic” phase content in the alloy is shown (the microhardness decreases as the total content of carbon and oxygen in the deposited layer increases). Sclerometric tests have shown that microhardness increases with an increasing tungsten concentration in the deposited layer.     

Thermodynamic properties of liquid glass-forming Ca–Mg alloys

The complex formation model was used to investigate the thermodynamic properties of liquid Ca–Mg glassy alloys. Our expressions reproduce the thermodynamic functions such as free energy of mixing, enthalpy of mixing, entropy of mixing and activity ratio. The study of long wavelength concentration–concentration fluctuations (S_CC(0)) provides structural information about liquid glass-forming Ca–Mg alloys. Chemical short range order parameter (₁) was obtained from S_CC(0) to quantify the degree of order. The study reveals that the formation of more than one type of complex may be related to the process of glass formation.     

Mg对Al-Zn-Sn阳极合金组织与电化学性能的影响

为提高Al-7Zn-0.1Sn(质量分数,%)牺牲阳极的电化学性能,采用扫描电镜(SEM)、透射电镜(TEM)、动电位极化、电化学阻抗等方法,研究了不同含量的Mg对Al-7Zn-0.1Sn合金微观组织和电化学性能的影响。结果表明:Mg可使Al-7Zn-0.1Sn合金从粗大枝状晶向等轴晶转变;适量Mg可改善Al-7Zn-0.1Sn合金的电化学性能;随着Mg含量增加,合金电位负移、电流效率逐步提高;当Mg含量为2%时,合金具有最好的综合电化学性能。     

Cu、Mg含量对Al-Cu-Mg-Fe-Ni铝合金组织性能的影响

采用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、拉伸力学性能测试及热力学计算等手段,研究了Cu、Mg成分对Al-Cu-Mg-Fe-Ni合金中形成S(Al2Cu Mg)相的数量及其室温力学性能的影响,为优化Al-Cu-Mg-Fe-Ni合金中Cu、Mg成分奠定基础。结果表明:Al-Cu-Mg-Fe-Ni合金中S(Al2Cu Mg)相的数量主要取决于Cu元素的含量;增加合金中的含Cu量,可获得较大数量的S(Al2Cu Mg)相,大大提高了合金的室温强度;Mg元素在形成S(Al2Cu Mg)相后仍有富余,过量的Mg溶于α(Al)中产生固溶强化作用,使合金室温强度得到提高。     

Effect of alloying on the properties of Mg−Gd alloys

Conclusions Alloy IMV7 of the Mg–Gd–Y–Mn system has high ultimate strength and long-term strength and can be used as a structural material for operation at room and elevated temperatures (up to 350°).Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 62–64, November, 1979.     

钛合金超音频直流脉冲GTAW焊缝组织性能

基于1.5 mm厚Ti-6Al-4V(TC4)钛合金平板对接试验,研究分析了超音频直流脉冲氩弧焊焊缝金相组织及焊接接头力学性能.结果表明,与常规直流钨极氩弧焊(gas tungsten arc welding,GTAW)相比,由于超音频直流脉冲方波电流的作用,气泡逸出速度增大,Ti-6Al-4V钛合金焊缝的气孔敏感性降低,熔池高温液态金属流动性增强,电弧能量集中,焊缝晶粒细化明显,其亚晶组织以短棒状a’马氏体组成的网篮状组织或a’片状组织与短棒状a’相交织的状态为主,焊接接头断后伸长率和断面收缩率显著提高.     

Sr对AZ91镁合金组织及力学性能的影响

采用光学显微镜、扫描电子显微镜和X射线衍射仪等研究Sr对AZ91镁合金组织及力学性能的影响.结果表明:添加微量Sr可以细化并离散AZ91合金的铸态共晶组织,在合金晶界处Sr与Al生成多角块状或杆状的Al4Sr高熔点相;当Sr含量为0.2%时,AZ91-0.2Sr合金的综合力学性能最优,AZ91-Sr合金的时效进程与AZ91合金相比明显被抑制.由于这些析出相及合金晶界附近Al4Sr高熔点相的强化作用,AZ91-0.2Sr合金经T6处理后的室温和高温力学性能皆优于原AZ91合金的.     

镁合金表面纳米TiSiN复合薄膜的制备及其结构和耐蚀耐磨性能分析

为提高镁合金耐蚀和耐磨性,扩大其在航空领域的应用,采用反应磁控溅射法,分别在AZ31和Mg8Li两种镁合金基体上制备了复合TiSiN薄膜. 采用X射线荧光光谱、扫描电镜、原子力显微镜和X射线小角掠入射分别对薄膜表面元素分布、形貌、膜层结构和晶粒尺寸进行了分析. 采用电化学工作站和球盘式摩擦磨损试验机分别对薄膜在3.5%NaCl溶液中的腐蚀行为和在空气中的摩擦磨损性能进行了研究. 结果表明,薄膜中Ti和Si元素比例与靶材相近,元素在整个膜层表面呈高低交替的环形分布,Mg8Li基体上薄膜的分布较为均匀;薄膜主要由TiN和Ti₂N两相组成,AZ31表面薄膜的晶粒尺寸和粗糙度均小于Mg8Li表面的薄膜;两种基体镀膜后的腐蚀电流密度降低了三个数量级,摩擦系数低于0.4,磨损率在10?6 m3/Nm数量级.     

正挤压-扭转剪切变形对镁合金组织与性能的影响

用光学显微镜、X射线衍射仪以及电子万能试验机,研究了正挤压-扭转剪切变形对AZ31、AZ61和AZ80镁合金组织和力学性能的影响。结果表明,经正挤压-扭转剪切变形后,镁合金发生了显著的晶粒细化和基面织构弱化,其中：AZ61镁合金发生了充分的动态再结晶,可将晶粒尺寸显著细化至3 μm,随挤压温度的升高,晶粒有所长大,基面织构受位错脱钉作用而进一步弱化。AZ31镁合金在挤压温度为250℃时获得优良的力学性能,其压缩率和抗压强度分别高达29.2%和395 MPa     

掺Cr纳米晶Mg2 Ni合金的气态储氢性能

纳米晶MgNi1-xCrx(x=0,0.1,0.2,0.3)合金由纯Mg、Ni、Cr粉在500℃经3h烧结后机械球磨而成。在210℃吸氢、250℃放氢的条件下，添加Cr后合金的最大吸放氢量明显提高；纳米Mg2Ni0.8Cr0.2合金的气态储氢量和吸氢动力学性能较好，第一次放氢量就达到3．0％，并且循环稳定性良好，吸氢后生成Mg2NiH4、Mg2NiH0．24相。纳米Mg2Ni0.7Cr0.3合金的放氢量在不经过活化的条件下便达到最大值，然而循环稳定性差，这是由于循环过程中有MgH2生成而造成的。     

An irreversible dipping sealing technique for anodized ZE41 Mg alloy

Anodized coatings are porous and sealing has been considered to be an essential step for anodized magnesium alloys. In this study, a new sealing technique was proposed and validated. Anodized ZE41 was dipped in an E-coating bath solution for a few seconds. After baking, the specimen was found to have considerably improved corrosion resistance. The corrosion rate and polarization current densities were found to be more than 3 orders of magnitude lower and the film breakdown potential over 50 mV higher for the anodized ZE41 after sealing in the E-coating bath solution than for the as-anodized ZE41. An irreversible electroless E-coating deposition model and corrosion mitigation mechanism for a sealed specimen are proposed.     

Mg元素对Al-Cu-Ce共晶合金导热和力学性能的影响

本研究以共晶型Al-14Cu-7Ce合金作为研究对象,通过调整Mg元素的添加量,探究其微观组织演变与导热和力学性能的变化规律。结果表明,铸态Al-14Cu-7Ce合金主要由α-Al和Al8CeCu4两相组成,其微观组织由粗大的共晶组织(α-Al+ Al8CeCu4)构成。添加少量Mg元素可细化该共晶组织,提高其力学性能。当Mg元素的添加量为1.0%时,合金的屈服强度和抗拉强度分别提升至164 MPa和263 MPa,提升幅度为29%和19%,断后延伸率提升至4.5%,提升幅度为约41%,导热率为130.2 W/(m·K),下降幅度约为12%。随着Mg元素进一步添加至2.0%,合金的力学性能指标有所下降,其屈服强度和抗拉强度分别降至151 MPa和249 MPa,其断后延伸率降为3.9%,导热率降至108.3 W/(m·K)。合金导热率下降主要原因是固溶的Mg原子形成散射源,阻碍电子在晶格内的运动,减小了电子和声子的平均自由程。当Mg添加量达到2.0%时,Mg与Al和Cu元素发生冶金反应生成Al2MgCu相,以鱼骨状共晶组织(α-Al+ Al2MgCu)形式分布于晶界处,增加合金中第二相的体积分数,进一步恶化合金的导电导热性能。而合金的力学性能下降主要由于存在 (α-Al+ Al8CeCu4)和(α-Al+ Al2MgCu)两种共晶组织,增加相界面处微裂纹萌生的位点。综上所述,添加1.0%Mg元素可获得兼具高强度和高导热的Al-Cu-Ce共晶合金。