复合合金化对AZ91镁合金铸态组织的影响

利用光学显微镜、扫描电镜和X射线衍射仪研究了0.5?、0.2?、0.2%Sr(质量分数,下同)复合合金化对AZ91合金铸态组织影响。结果表明,0.5?、0.2?、0.2%Sr复合加入可以显著细化合金的铸态组织,0.5?、0.2?、0.2%Sr同时加入,其细化效果优于0.5?和0.2?或0.5?和0.2%Sr的复合加入,并且在组织中出现针状或杆状的Al4Ce新相。     

碱土元素对AZ91D镁合金组织和性能的影响

通过向AZ91D合金中添加Ca、Ba、Sr3种碱土元素,熔炼制备了铸态镁合金,利用OM、SEM、EDS和XRD等手段研究了合金的铸态组织和物相组成,测试了其力学性能.结果表明, Ca、Ba、Sr的综合作用可以显著细化镁合金的铸态组织,并使网络状β-Mg17Al12相以球块状弥散分布,室温抗拉强度从AZ91D合金的156.3 MPa提高到AZ91D-0.5Ca-0.2Ba-0.1Sr合金的187.6 MPa.     

阻燃镁合金AZ91D的研究

研究了通过添加铍，可得到直接暴露在大气中熔炼的镁合金AZ91D。通过金相组织观察发现：当铍的含量达到0.015%时，合金的晶粒度最好，而且具有很好的阻燃性能；同时研究了采用不同的变质剂AZ91D合金进行变质处理。实验结果表明：变质处理的AZ91D合金，组织明显细化，尤其是时效处理后，其力学性能得以大幅度提高，拓宽了合金的使用范围。     

提高AZ91镁合金耐蚀性的研究进展

综述了合金元素和化学转化处理、微弧氧化、金属镀膜等表面处理技术对AZ91合金耐蚀性影响。分析了AZ91合金的腐蚀行为,总结了提高AZ91合金耐蚀性的主要途径。并提出了进一步研究复合合金化、不同表面处理技术的结合以及添加合金元素与表面处理技术的结合等方法。     

AZ91镁合金挤压组织和性能研究

对AZ91镁合金铸锭进行（410±5）。C×10h的固溶处理后，在330。C以挤压比为25：1进行了挤压，研究了其组织和性能。结果表明，挤压AZ91镁合金具有较细的晶粒组织，第二相Mg17，A112被破碎，其分布变得弥散，个别呈流线分布；挤压AZ91镁合金比铸造AZ91镁合金的力学性能有较大提高，其屈服强度为210MPa，抗拉强度为355MPa，伸长率为18％。第二相Mg17，Al12对镁合金的性能具有重要影响。     

合金元素对AZ91镁合金组织和性能影响的研究进展

综述了国内外对AZ91镁合金的研究现状,介绍了稀土、碱土和第Ⅳ、Ⅴ族元素三类不同合金化元素对AZ91镁合金组织和性能的影响,并展望了未来提高AZ91镁合金耐热性的发展方向.     

Ce含量对AZ91D镁合金组织及性能的影响

研究了不同Ce含量的AZ91D镁合金的晶粒尺寸、物相和力学性能。结果表明,Ce含量不同的AZ91D镁合金显微组织、物相和力学性能有较大差异;Ce含量在0.5%~1.5%范围内,随着Ce含量升高,晶粒尺寸逐渐细化;当Ce含量为1.5%时,晶粒尺寸最小,合金综合力学性能最高。     

AZ91镁合金耐腐蚀性能的研究进展

AZ91是工业上应用最为广泛的镁合金之一,但其较差的耐腐蚀性能阻碍了其进一步的推广应用.分析了AZ91合金腐蚀速率大小的几个主要影响因素,介绍了改善AZ91镁合金耐蚀性能的方法.     

合金化对AZ91D镁合金组织与力学性能的影响

利用光学显微镜（OM）和X射线衍射（XRD）分析了分别加入合金化元素Ce，Si和Ca后AZ91D合金的铸态组织和相组成，测试了合金室温拉伸性能和硬度。结果表明：加入Ce和Si后合金组织中分别生成杆状Al4Ce和汉字状Mg2Si相，而加入Ca后无新相生成，加入的Ca主要固溶于β相中；Al4Ce和Mg2Si相在合金凝固过程中被推移到生长界面，Ca原子偏聚在生长界面前沿，从而阻碍枝晶的自由生长，细化合金铸态组织：Ce和Ca的加入可提高合金室温综合力学性能，且前者提高程度要高于后者提高程度，而Si的加入却降低合金室温综合力学性能。     

激光合金化对AZ91D镁合金力学性能的影响

在AZ91D镁合金表面预置A1粉,采用5 kW横流CO2激光器对其进行合金化处理.采用电子探针对合金化层的元素分布进行分析.使用X射线衍射仪和扫描电子显微镜(SEM)对合金化层进行微观分析,测试涂层的摩擦磨损性能.结果表明:合金化层主要由α-Mg和B-Mg17Al12组成;合金化层的磨损性能与基体相比有了较大提高.     

铸造AZ91D镁合金的遗传性

试验研究了具有不同铸造组织形态的AZ91D镁合金和具有不同晶粒度的AZ91D镁合金重熔前后的组织和性能的变化规律。结果表明,重熔前后的AZ91D镁合金的组织和性能具有相同性或相似性,在铸造过程中具有明显的遗传性。     

Corrosion performance of magnesium alloys MEZ and AZ91

The corrosion performance of sand cast MEZ_S, zirconium-grain-refined MEZ_R, sand cast AZ91_S, and high pressure diecast AZ91_D magnesium alloys were evaluated by means of salt spray testing, optical metallography, hydrogen evolution, polarisation curve measurement and AC impedance spectroscopy. The results show that the corrosion resistance of the four alloys can be ranked in decreasing order as AZ91_D > AZ91_S ≈ MEZ_R > MEZ_S and that the intergranular phases and chemical composition of the matrix phase have a significant influence on the corrosion performance. Alloys with a finer grain size and higher aluminum or zirconium contents exhibit better corrosion resistance.     

汽车用AZ91镁合金的耐腐蚀性能

以AZ91镁合金为研究对象,研究了NaCl溶液的浓度、腐蚀时间、温度和搅拌速度对AZ91镁合金耐腐蚀性的影响。利用扫描电镜观察了腐蚀后的表面形貌和横截面形貌,定性分析了AZ91镁合金在NaCl溶液中的腐蚀行为。结果表明,随NaCl溶液浓度、腐蚀时间、温度和搅拌速度增加,AZ91镁合金腐蚀速率主要呈递增趋势,且腐蚀形式为沿晶腐蚀。     

Effect of heat diffusion on properties of zinc-aluminum coating on AZ91D magnesium alloys

A protecting zinc and aluminum coating on the surface of AZ91D magnesium alloys was obtained by thermal spraying to improve the corrosion and wear resistance performances. In order to enhance the combination between magnesium alloy matrix and zinc and aluminum coating, the sample was heat-treated at 300 ℃ for 2 h, then, the cross-section patterns, XRD pattern, micro-hardness, wear and corrosion resistance abilities were researched. The results indicate that the interface between the coating and substrate is metallurgical bond, and a transitional fusion layer is formed by diffusion. The micro-scale abrasion test and polarization test in 3% NaCl solution show that the diffusion-treated specimen has better wear and corrosion resistance performances in comparison with the undiffusion-treated and substrate magnesium alloys; in addition, it has relatively higher micro-hardness than the undiffusion-treated magnesium alloys.     

Formation of micro-arc oxidation coatings on AZ91HP magnesium alloys

In a neutral solution, coating formation by micro-arc oxidation (MAO) on AZ91HP magnesium alloy was studied. The process involved the substrate dissolution and coating development. During the first 5 s, the sample mass decreased, indicating substrate dissolution dominating the process. After 5 s, the sample mass began to increase and the coating development began to predominate the process. The coating was firstly nucleated on α phase and sparks initially appeared mainly on the edges of the sample. With treating proceeded, the coating was becoming uniform; meanwhile, microscopic pores of anodic coatings increased in size and decreased in number.     

AZ91D变形镁合金的动态应变时效现象

在应变速率为1.11×10-4～1.67×10-3s-1、温度为248～523K的条件下,对固溶态AZ91D变形镁合金进行拉伸试验。结果表明:在一定的拉伸应变速率和温度区间拉伸时,AZ91D镁合金在形变过程中发生动态应变时效(DSA)现象,其典型特征表现为其拉伸曲线出现锯齿波,所对应的锯齿波类型分别呈A型及A+B混合型;应变速率敏感性系数为负值;且出现加工硬化速率峰值;出现锯齿屈服的临界应变量随变形温度升高而减小,而随应变速率增加而增大;当形变温度大于323K时,加工硬化速率随着温度升高反而急剧增大,在368K时达到峰值。     

Flow stress modeling of AZ91 magnesium alloys at elevated temperature

The flow curve is constructed by flow stress data obtained from compression test conducted at different temperature and strain rate. Accurate flow stress model is crucial for investigating magnesium alloys deformation behaviour at the elevated temperatures. An analytical method, which reflects temperature, strain and strain rate effect by introducing temperature-compensated strain rate (Zener-Hollomon Parameter), is proposed in this study. This model has been applied on the experimental data and predicted flow stress curve match well with those measurements.     

Fabrication of quaternary Mg-Zn-Y-Ce quasi-crystal alloys and their strengthening effects on AZ91 magnesium alloys

Quaternary Mg-Zn-Y-Ce quasi-crystal-containing alloys were fabricated using a metal mold casting route.The microstructures of Mg-Zn-Y-Ce alloys and the distribution of the major elements were analyzed.The differences in morphology and micro-hardness between quaternary Mg-Zn-Y-Ce quasi-crystals and ternary Mg-Zn-Y quasi-crystals were discussed.The result showed that the micro-hardness of Mg-Zn-Y-Ce quasi-crystals reached peak value when the content of Ce was 0.8at.%.Subsequently,various contents of Mg-Zn-Y-0.8Ce alloys were used to strengthen AZ91 magnesium alloys.The microstructural modification and mechanical properties of reinforced AZ91 alloys with and without solution,as well as their aging treatments,were also studied.Further research showed that aging-treated AZ91-10wt.%(Mg-Zn-Y-0.8at.%Ce) alloys exhibited excellent mechanical properties:their Brinell hardness,tensile strength,and elongation were HV91,252 MPa,and 4.1%,respectively.Through this study,the range of application of AZ91 alloys can further be extended.     

AZ91镁合金热塑性的试验研究

对铸态和均匀化退火的AZ91镁合金进行不同温度、不同应变速率的热模拟试验,研究了其高温热塑性.结果表明,与铸态合金相比,经均匀化退火的AZ91镁合金断面收缩率有较大提高,抗拉强度明显降低;当变形温度在300℃～420℃时,断面收缩率先增大后减小,在380℃～400℃之间达到最大值,抗拉强度趋势呈近似直线递减.在380℃～400℃范围内变形,塑性最好.均匀化处理的合金,在应变速率为0.05 s-1、0.5 s-1、5 s-1时进行热模拟,断面收缩率在变形温度为380℃时达到最大.在不同变形温度下,应变速率减小,断面收缩率增大,抗拉强度降低,塑性提高.