AZ31镁合金微弧氧化膜的电化学腐蚀性能

选用碱性硅酸盐溶液,对AZ31镁合金进行微弧氧化处理,获得了由厚度为3 μm的致密层和厚度为22 μm的疏松层组成的双层结构膜,主要由MgO、Mg2SiO4、Mg2SiO3组成.用测量阳极极化曲线与电化学阻抗谱(EIS)的方法研究了微弧氧化AZ31镁合金的电化学腐蚀行为.在pH12的0.5 mol/L NaCl溶液中,微弧氧化AZ31镁合金阳极极化曲线山原始镁合金的活化溶解转变为自钝化一点蚀击穿过程,自腐蚀电流密度降低1个数量级.原始AZ31镁合金的EIS呈现一个容抗弧和一个感抗弧,发生均匀腐蚀,感抗弧的出现表明电极反应过程中存在中间产物Mg ;微弧氧化AZ31镁合金浸泡96 h后EIS呈现三个容抗弧和一个的感抗弧,感抗弧的出现表明发生局部腐蚀,并且容抗弧直径较原始合金相比增大近5倍,微弧氧化膜阻碍了Cl-离子的扩散和迁移,合金的耐蚀性能显著提高.     

AZ31B镁合金电子束焊接接头显微组织及疲劳性能

为了改善镁合金焊接接头的微观组织及其力学性能,采用真空电子束焊接工艺对厚10 mm的AZ31B镁合金板材进行焊接,分析电子束对接接头的显微组织、元素分布和物相组成,检测了电子束对接接头静载拉伸性能和疲劳性能.试验结果表明AZ31B镁合金电子束焊接接头的微观组织和力学性能均得到了改善:焊缝区晶粒明显细化,焊缝区Mg、Zn元素的质量分数分别降低了0.12%和0.28%,Al、Mn元素的质量分数分别增加了0.24%、0.14%,焊缝区为单相α-Mg,无明显的低熔点β-Mg17Al12脆性;焊接接头的抗拉强度为242 MPa,能够达到母材的抗拉强度;在脉动载荷（R=0.1）、2×106循环次数下,其接头的疲劳强度为91 MPa,能达到母材的78.4%.      

镁合金AZ31的差热分析及凝固组织观察

利用差热分析（DTA）和在不同温度下加热-急冷,并结合金相组织观察的方法研究了AZ31镁合金的凝固相变温度及凝固组织变化特征．通过对AZ31镁合金DTA曲线的分析和不同温度下金相组织的比较、分析,确定了该合金的相变起始温度为430．1℃,共晶温度为438．5℃,固相线温度为614．4℃,液相线温度为636．4℃．同时,通过对不同温度下急冷试样的组织观察,分析了AZ31镁合金在凝固过程中的相变及组织演变特征,并确定了差热分析所得相变温度的准确性．     

镁合金AZ31的差热分析及凝固组织观察

利用差热分析(DTA)和在不同温度下加热-急冷,并结合金相组织观察的方法研究了AZ31镁合金的凝固相变温度及凝固组织变化特征.通过对AZ31镁合金DTA曲线的分析和不同温度下金相组织的比较、分析,确定了该合金的相变起始温度为430.1℃,共晶温度为438.5℃,固相线温度为614.4℃,液相线温度为636.4℃.同时,通过对不同温度下急冷试样的组织观察,分析了AZ31镁合金在凝固过程中的相变及组织演变特征,并确定了差热分析所得相变温度的准确性.     

AZ31镁合金在Na2SO4溶液中的电化学腐蚀行为

将AZ31镁合金在pH6.1的0.1mol/L Na2 SO4溶液中长时间浸泡,利用X射线衍射(XRD)和扫描电子显微镜(SEM)分析不同浸泡时间腐蚀产物膜的相结构和形貌变化;利用阳极极化和电化学交流阻抗谱(EIS)测量技术研究AZ31镁合金腐蚀产物膜的形成过程及浸泡时间对合金耐蚀性能的影响规律.研究结果表明:AZ31镁合金在0.1mol/L NaSO4溶液中可形成固态的多孔氧化膜,腐蚀产物膜主要由MgSO4组成;随着浸泡时间的延长,腐蚀产物膜在合金表面的覆盖率和厚度逐渐增加,阳极极化曲线呈现类似于自钝化的现象,且自腐蚀电位逐渐升高,腐蚀电流密度减小,表明腐蚀产物膜对基体具有一定的保护作用;腐蚀产物成膜过程中的EIS均呈现两个容抗弧,具有两个时间常数,两个容抗弧的直径均随浸泡时间的增加而增大,同时相位角平台变宽,相位角提高,说明腐蚀产物膜的厚度越厚,对阻碍反应离子向基体扩散和迁移的影响越大.     

AZ31镁合金的电化学腐蚀行为

采用阳极极化和电化学阻抗谱(EIS)技术研究了AZ31镁合金的电化学腐蚀行为.阳极极化结果表明:AZ31镁合金在中性NaCl溶液中发生活化溶解,随Cl-浓度增加,腐蚀速率增加;在不同pH溶液中,随pH值增大发生由活化溶解向自钝化的转变,临界值为pH=10.5.电化学阻抗谱结果表明:在Ecorr-100mV电位下,阻抗谱由单一容抗弧组成,等效电路为Rs(QRt),表征析氢反应过程;在Ecorr电位和Ecorr 100mV电位下,阻抗谱由高频容抗弧和低频感抗弧组成,等效电路为Rs(QRt(LRL)),感抗弧的出现表明电极反应过程中存在中间产物Mg .     

微观组织结构对变形镁合金AZ80阻尼性能的影响

采用光学显微镜、扫描电镜和透射电镜观察了AZ80镁合金在挤压态、固溶态和时效态的显微组织,并用动态机械分析仪研究了不同微观组织状态下AZ80镁合金的阻尼性能.结果表明：AZ80合金在挤压过程中发生了动态再结晶,随后在410℃进行4 h固溶处理,强钉扎点数量减少,合金的阻尼性能提高,在170℃时效18 h由于第二相析出偏聚于晶界处,降低了晶内弱钉扎点的数量,且时效降温过程中,由于基体与析出相热膨胀系数的差异,导致产生新的位错,增大了位错密度,使阻尼性能进一步提高.该合金室温阻尼机制可用G-L位错钉扎模型解释.     

微观组织结构对变形镁合金AZ80阻尼性能的影响

采用光学显微镜、扫描电镜和透射电镜观察了AZ80镁合金在挤压态、固溶态和时效态的显微组织,并用动态机械分析仪研究了不同微观组织状态下AZ80镁合金的阻尼性能.结果表明:AZ80合金在挤压过程中发生了动态再结晶,随后在410℃进行4 h固溶处理,强钉扎点数量减少,合金的阻尼性能提高,在170℃时效18 h由于第二相析出偏聚于晶界处,降低了晶内弱钉扎点的数量,且时效降温过程中,由于基体与析出相热膨胀系数的差异,导致产生新的位错,增大了位错密度,使阻尼性能进一步提高.该合金室温阻尼机制可用G-L位错钉扎模型解释.     

超细Al_2O_3粉对AZ80镁合金耐腐蚀性的影响

采用热扩散的方法使超细Al2O3粉进入AZ80镁合金的表层以提高其耐蚀性.研究结果表明,热扩散处理温度、处理时间与AZ80镁合金耐蚀性的提高关系密切.随处理时间的延长和处理温度的升高,合金的耐蚀性提高,腐蚀速率由未进行处理的153.75 mg/dm2.h降到13.75 mg/dm2.h,且存在一个最佳处理温度为410℃.     

超细Al2O3粉对AZ80镁合金耐腐蚀性的影响

采用热扩散的方法使超细Al2O3粉进入AZ80镁合金的表层以提高其耐蚀性.研究结果表明,热扩散处理温度、处理时间与AZ80镁合金耐蚀性的提高关系密切.随处理时间的延长和处理温度的升高,合金的耐蚀性提高,腐蚀速率由未进行处理的153.75 mg/dm2·h降到13.75 mg/dm2·h,且存在一个最佳处理温度为410℃.     

Experimental exploration of electrical pulse-assisted roller hemming of AZ31B magnesium alloy sheet

The purpose of this research is to explore the feasibility of roller hemming of AZ31B magnesium alloy sheet. During the test, a special experimental setup considering the current flow and insulation was designed and employed. For the sake of simplicity, the flat surface-straight edge hemming style was selected. Electrical pulses were introduced in the pre-hemming and final hemming processes. The results show that when hemming at 448 K with hemming speed of 30 mm/min, AZ31B magnesium alloy sheet was successfully hemmed with excellent perceived quality. No recoil/warp defect, cracking or springback was observed. Electrical pulses induced dynamic recrystallized grains were observed along the grain boundaries in the severely deformed area, which is of great importance to the improvement of the ductility of the material. The hardness was slightly increased after hemming with electrical pulses, and this fact could improve the friction resistance performance of the hemmed part.     

Microscopic structure and property of double-electrode gas metal arc welding of AZ31B magnesium alloy

This paper focuses on the research on double-electrode gas metal arc welding(DE-GMAW) of AZ31 B magnesium alloy sheet with 2 mm thickness. During the welding process, stable hybrid arc of metal inert gas(MIG) and tungsten inert gas(TIG) is employed as welding heat source. Optical and electron microscopes are used to observe the microstructures of the weld joint. X-ray diffraction(XRD) and energy dispersive spectroscopy(EDS) are employed to identify the components in fusion zone. Microhardness is also tested. When the MIG current is 80 A, the perfect weld joint is obtained, though figures of fish scales are observed in all joints in the research. The fusion zone is formed by dendrites, where β-Mg17(Al, Zn)12is dispersed. The hardness in fusion zone and heat affected zone(HAZ) is lower than that in base metal(BM). The average Vickers hardness of fusion zone and HAZ is about 58 and 56 respectively, while the Vickers hardness of BM is about 63.     

Polycrystalline behavior analysis of extruded magnesium alloy AZ31

Uniaxial tensile and compressive tests were performed at room temperature on extruded AZ31 Mg alloy specimens and distinct tensile-compressive anisotropy was detected. Deformed specimens were examined and the results indicate that the generation of {10 $\bar 1$ 2}〈10 $\bar 1$ 1〉 twin is responsible for the mechanical anisotropy. A rate independent crystal plasticity model, which accounts for both slip and twinning, was developed for polycrystalline hexagonal close packed (HCP) materials. Model predictions for the stress-strain curves and texture evolution were in reasonable agreement with the experimental results. Specifically, the model captured the three stages of strain hardening for uniaxial-compression. By comparing stress-strain curves and texture evolution between model predictions and experimental measures, information about the dominant slip and twinning systems active at room temperature was deduced.     

膏剂法渗铝工艺及性能的研究

研究了膏剂法渗铝中渗剂的配比、渗铝时加热温度和保温时间以及粘结剂的类型对Q235钢表面渗铝层的组织和抗高温氧化性能的影响.结果表明:膏剂法渗铝时,随渗剂配比中铝粉含量的增加,渗铝层深度增加;但当铝粉含量达到35%时,表面粘铝现象较严重.因此铝粉的含量最好是在20%～30%范围内.而且渗铝时加热温度越高,保温时间越长,渗铝层深度越深.粘结剂的酸碱性也对试样表面渗铝层的深度有影响,采用的粘结剂最好为中性的聚乙烯醇.不论是何种渗剂配比,渗铝后其试样的抗氧化能力均比未处理的高.并且渗剂配比中铝粉含量越高,其抗氧化能力就越高.     

膏剂法渗铝工艺及性能的研究

研究了膏剂法渗铝中渗剂的配比，渗铝时加热温度和保温时间以及粘结剂的类型对Q235钢表面渗铝层的组织和抗高温氧化性能的影响。结果表明：膏剂法渗铝时，随渗剂配比中铝粉含量的增加，渗铝层度增加；但当铝粉含量达到35％时，表面粘铝现象较严重。因此铝粉的含量最好是在20％－30％范围内，而且渗铝时加热温度越高，保温时间越长，渗铝层度越深。粘结剂的酸碱性也对试样表面渗铝层的深度有影响。采用的粘结最好为中性的聚乙烯醇，不论是何种渗剂配比，渗铝后其试样的抗氧化能力均比未处理的高，并且渗剂配比中铝粉含量越高，其抗氧化能力就越高。     

Influence of high frequency vibration on deep drawing process of AZ31 sheet at room temperature

Quasi-ultrasonic vibration with a frequency of 15 kHz and a maximum output of 2 kW was imposed on the deep drawing process of AZ31 magnesium alloy sheet at room temperature, in order to reveal the effect of high frequency vibration on deformation behavior of AZ31 during the process. From the drawn results and the observation of the microstructure within the large deformation area, high frequency vibration has a great influence on the formability, the forming load and the failure mode of AZ31 sheet during the deep drawing process; the influence is a comprehensive result of so-called ??volume effect?? and ??surface effect??, and relies on the vibrating amplitude. Total forming load decreased significantly as soon as the vibration superimposed. According to the tensile test results of AZ31 bars under ultrasonic vibration, the formability of AZ31 sheet increases firstly with the increase of stimulating energy, then decreases and finally becomes brittle. Under the combined influence of ??surface effect?? and the ??softening?? in the ??volume effect?? near the relative low amplitude of 25%A in the experiment (A is the maximum amplitude), the formability of AZ31 reaches the largest value, and the samples possess the same distribution trend of cracks as those added with lubricating oil. With the increase of excitation energy, the ??volume effect?? gradually becomes apparent, and finally the ??hardening?? of the ??volume effect?? occupies a dominant position.     

铁基非晶合金非晶形成能力的分子动力学模拟

采用分子动力学方法,模拟了Fe60 Cr20 Mo20和Fe50 Cr20 Mo20 M10（ M＝Ni, W）铁基非晶合金的形成过程,通过加热至熔融态再淬火的方法计算出了了Fe60 Cr20 Mo20、Fe50 Cr20 Mo20 M10和Fe50 Cr20 Mo20 W10三种合金形成非晶的临界冷速及一系列热力学参数。结果表明,三种合金形成非晶的临界冷速分别为15．7 K/ps、3．62 K/ps和1．04 K/ps,四元合金较三元合金形成非晶所需的临界冷速大大降低,而W元素的添加更能提高合金的非晶形成能力。另外,通过热力学参数分析,Fe50 Cr20 Mo20 W10合金的约化玻璃转变温度Trg较大为0．626,也说明其具有较好的非晶形成能力。