原位合成TiC_p/AZ91D镁基复合材料的高温流变行为

采用原位合成法制备了TiCp/AZ91D镁基复合材料,研究了其高温流变行为。结果表明,铸态TiCp/AZ91D镁基复合材料在高温压缩变形过程中存在稳态流变特征,流变应力随着温度的升高和应变速率的降低而降低。在较低温度范围内,TiC颗粒强化效果明显。随着温度的升高,增强相对基体AZ91D镁合金的增强效果逐渐消失。     

Al2O3-SiO2/AZ91D镁基复合材料的制备及其性能研究

采用硅酸铝纤维和镁合金制备出结构紧密的Al2O3-SiO2/AZ91D镁基复合材料.适宜的挤压铸造工艺为:预制体温度650 ℃、模具温度550 ℃、浇注温度760 ℃和压力30～50 MPa.XRD、SEM、EDS和OM等分析结果表明,复合材料主要由Mg、β-Mg17Al12、MgO、AlPO4、3Al2O3·2SiO2和Mg2Si等结晶相组成;镁与硅酸铝纤维反应生成MgO和汉字状Mg2Si等产物;基体镁与硅酸铝纤维的界面形成比较紧密的结合层.与镁合金相比,复合材料的硬度和油摩擦性能有较大提高.     

Al2O3-SiO2/AZ91D镁基复合材料制备及界面反应机理研究

采用硅酸铝纤维和镁合金制备出结构紧密的Al2O3-SiO2/AZ91D镁基复合材料。介绍了复合材料的制备工艺,适宜的挤压铸造工艺为预制体温度650℃、模具温度550℃、浇注温度760℃和30～50MPa压力。XRD、SEM、EDS和光学金相显微镜OM等分析结果表明,复合材料主要由Mg、β-Mg17Al12、MgO、AlPO4、3Al2O3·2SiO2和Mg2Si等结晶相组成;镁与硅酸铝纤维反应生成MgO和汉字状Mg2Si等产物;基体镁与硅酸铝纤维的界面形成较紧密的结合层。     

SiC对AZ91D镁合金晶粒细化效果的影响

研究了SiC对AZ91D镁合金组织的影响.通过在不同温度添加不同含量的Mg-SiC混合粉末,在760～780 ℃、SiC含量为0.20%时,AZ91D镁合金晶粒达到75 μm.利用光学显微镜和扫描电子显微镜及其电子探针观察发现,Mg-SiC混合粉末的加入使得AZ91D镁合金的晶粒尺寸显著减小,这是因为Mg-SiC混合粉末加入后反应生成了少量的Al4C3,Al4C3颗粒可以作为α-Mg的结晶核心,同时SiC颗粒本身也可以作为α-Mg的异质结晶核心.对于AZ91D合金而言,Mg-SiC混合粉末是一种良好的晶粒细化剂.     

挤压铸造SiC_p/AZ91D镁基复合材料的试验研究

以AZ91D镁合金和平均颗粒尺寸为0.5μm的SiC颗粒分别作为基体和增强相,通过全液态搅拌铸造法和挤压铸造法结合制备出SiC颗粒增强镁基复合材料。力学性能测试结果显示:当模具温度为200℃、保压时间为15 s时,SiCp/AZ91D镁基复合材料抗拉强度最高为157 MPa;金相显微组织显示,碳化硅颗粒可作为镁合金凝固时异质形核的中心,也可能会随着凝固时固液界面的推移,使SiC颗粒处于晶界处;存在SiC颗粒团聚现象,这是其抗拉强度降低的原因;SiCp/AZ91D镁基复合材料在室温下拉伸时的断口形貌呈现脆性断裂特征;热处理工艺为固溶处理温度420℃,保温20 h空冷,时效处理温度200℃,保温8 h空冷,经过热处理后,镁基复合材料的抗拉强度均有所提高,最高可提高48.95%。     

原位反应自发渗透法TiC／AZ91D镁基复合材料及AZ91D镁合金的拉伸变形与断裂行为

利用原位反应自发渗透技术合成了47．5％碳化钛TiC（体积分数，下同）增强AZ91D镁基复合材料，对比研究了该复合材料与铸态镁合金AZ91D基体的室温与高温拉伸变形行为，观察了拉伸断口微观组织形貌，并分析了这两种材料的断裂特征。结果表明，TiC／Mg复合材料具有良好的高温力学性能，在拉伸变形速率为0．001s^-1以及温度为723K，时其拉伸强度可达91．1MPa，而此时相同变形条件下的铸态AZ91D镁合金拉伸断裂强度只有41．1MPa，增幅达120％。而在室温下，镁基复合材料的拉伸断裂强度仅高出基体铸态镁合金23．4％。镁基复合材料的断裂应变较低，高低温时均表现为脆性断裂；而镁合金则由室温下的脆性断裂向高温下的韧性断裂过渡。     

Er对铸态AZ91镁合金显微组织和耐腐蚀性能的影响

利用金相显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射分析、集气法及动电位极化曲线研究了微量Er对铸态AZ91镁合金显微组织和腐蚀性能的影响.结果表明:微量Er可细化AZ91镁合金的铸态组织,当AZ91镁合金中加入Er的含量不高于0.7%(质量分数)时,随着Er含量的增加,镁合金中的γ-Mg17Al12相由粗大、连续块状分布逐渐转变为细小、岛状均匀分布,并且有Al3Er相生成;同时,微量Er也可显著提高铸态AZ91的耐腐蚀性能,当Er含量为0.7%时,合金耐蚀性能大幅度提高,在3.5%(质量分数)NaCl水溶液中浸泡的腐蚀速率为0.546 06 mg/(cm2·d),仅为常规AZ91镁合金的1/15;微量Er使得AZ91镁合金在3.5% NaCl溶液中的自腐蚀电位升高,自腐蚀电流降低,从而提高AZ91镁合金的耐腐蚀性能.     

Ca及Ce低合金化对TiC_p/AZ91镁基复合材料组织性能的影响

将加入Ca及Ce元素低合金化和采用XD法制备的Ti Cp/Al预制块相结合,并进行半固态搅拌的方法制备Ti Cp/AZ91镁合金复合材料,对其显微组织和力学性能进行分析测试。结果表明:加入0.3wt%Ca、0.3wt%Ce后,AZ91镁合金与Ti Cp/AZ91镁基复合材料的组织明显细化,β-Mg17Al12相减少。少量Ca、Ce的加入有利于熔炼时镁合金的熔体保护,可减少细小Ti C粒子的团聚,提高抗拉强度及伸长率。     

挤压铸造准晶增强AZ91D镁基复合材料组织与性能

为了改善AZ91D镁合金的性能,采用挤压铸造法制备了Mg-Zn-Y准晶中间合金增强AZ91D镁基复合材料,研究了准晶中间合金含量对复合材料组织和性能的影响。结果表明挤压铸造工艺可以有效细化晶粒,复合材料的显微组织主要由α-Mg基体、晶界上分布的β-Mg17Al12相以及Mg3Zn6Y准晶颗粒组成,准晶颗粒和α-Mg基体之间形成稳定结合。当准晶中间合金含量为5%时,抗拉强度和断后伸长率达到最大值,分别为194.3MPa和9.2%。复合材料的强化机制为细晶强化和准晶颗粒强化。     

纳米SiC颗粒增强镁基复合材料的动态断裂行为研究

采用机械搅拌与高能超声处理相结合的分散法制备了纳米SiC颗粒增强AZ91D镁基复合材料(n-SiCp/AZ91D),利用动态SEM原位拉伸方法研究了纳米复合材料的断裂行为.结果表明:微裂纹主要在晶界上的β-Mg17Al12处萌生,并沿着晶界上的脆性相不断开裂和连接向前扩展,由于颗粒和界面的阻碍,裂纹扩展路径较长.AZ91D合金的裂纹也主要沿着晶界上的脆性相不断向前扩展,但裂纹扩展路径比较平坦,AZ91D合金在加载初期就萌生出大量的裂纹.     

汽车发动机用AZ91D合金的表面喷涂与性能

采用热喷涂工艺在压铸态AZ91D合金表面制备了Al涂层,研究了热处理温度和保温时间对AZ91/Al涂层界面组织形貌的影响,并对比分析了扩散层的耐腐蚀性能和耐磨性能。结果表明,热处理前Al涂层与基材为机械结合,热处理后Al涂层与AZ91合金基材的界面处可形成冶金结合扩散层,且随着保温时间延长,扩散层厚度不断增加;热处理温度在375 ℃以下时扩散层主要由β-Mg₁₇Al₁₂相构成,375 ℃×8 h热处理后为α-Mg+β-Mg₁₇Al₁₂相,425 ℃×1 h热处理后为γ-Mg₂Al₃和β-Mg₁₇Al₁₂相。AZ91合金基材和扩散层腐蚀电位从高至低顺序为γ>β>α+β>AZ91合金基材,扩散层的腐蚀电流密度均低于AZ91合金基材,阻抗谱图中容抗弧半径从大至小顺序为γ>β>α+β>AZ91合金基材,扩散层的耐腐蚀性能均优于AZ91合金基材;γ、β和α+β扩散层的摩擦稳定性系数都高于AZ91合金基材,而磨损速率和磨痕宽度都要小于AZ91合金基材,其中β扩散层的磨损速率和磨痕宽度最小,具有最佳的抵抗磨损的能力。     

Effects of in-situ ZrB2 particle on grain refinement of ZrB2/AZ91D magnesium matrix composite

In-situ ZrB2/AZ91D magnesium matrix composite was successfully synthesized with Al/K2ZrF6+NH4BF4 by means of Direct Melt Reaction.The fabricated ZrB2/AZ91D magnesium matrix composite through direct melt mixing method was investigated.Results from X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) confirmed the existence of ZrB2 particles in the AZ91D alloy,and most ZrB2 particles were in the size range of just several microns,some even to 100 nm.The cast specimens were studied through corrosion testing and heat treatment.The average grain size of AZ91D decreased markedly from about 250μm to 50μm.In addition,the shape and size of the β-Mg17Al12 phase as well as the morphologies of primary α-Mg in the magnesium matrix composite were greatly changed.The network structure of the β-Mg17Al12 phase was broken into small blocks and the size of α-Mg decreased significantly.     

K2Ti6O13/AZ91D镁基复合材料的组织及耐蚀性能

采用液态金属搅拌铸造法制备了K2Ti6O13晶须(PTW)增强AZ91D镁基复合材料,采用动电位极化测试和静态腐蚀试验测试了复合材料的耐腐蚀性能,并利用SEM对复合材料的表面形貌进行了观察和分析。结果表明:PTW对合金铸态组织具有明显的细化作用,而且共晶组织形貌发生明显改变,由完全离异共晶骨骼状的β相转变为部分离异共晶的蜂窝状β相。合金显微组织的细化及β相体积分数的降低,抑制了微电偶腐蚀的破坏作用,提高了AZ91D镁合金的耐蚀性能。     

Wear and corrosion properties of laser cladded Cu47Ti34Zr11Ni8/SiC amorphous composite coatings on AZ91D magnesium alloy

To improve the wear and corrosion properties of AZ91D magnesium alloys, Cu-based amorphous composite coatings were fabricated on AZ91D magnesium alloy by laser cladding using mixed powders of Cu47Ti34Zr11Ni8 and SiC. The wear and corrosion behaviours of the coatings were investigated. The wear resistance of the coatings was evaluated under dry sliding wear condition at room temperature. The corrosion resistance of the coatings was tested in 3.5% （mass fraction） NaCl solution. The coatings exhibit excellent wear resistance due to the recombined action of amorphous phase and different intermetallic compounds. The main wear mechanisms of the coatings and the AZ91D sample are different. The former is abrasive wear and the latter is adhesive wear. The coatings compared with AZ91D magnesium alloy also exhibit good corrosion resistance because of the presence of the amorphous phase in the coatings.     

TiC/AZ91D composites fabricated by in situ reactive infiltration process and its tensile deformation

1 Introduction Relative to aluminum matrix composites, magnesium-matrix composites are receiving interests increasingly in recent years due to their low densities and high specific properties. They are potentially attractive for the applications in aeros…     

Corrosion performance of laser-remelted Al-Si coating on magnesium alloy AZ91D

Laser remelting was applied to plasma-sprayed Al-Si coating on magnesium alloy AZ91D to improve corrosion performance. Both salt spray testing and potentiodynamic polarization measurement in 3.5% NaCl solution indicated that laser-remelted Al-Si coating acquired better corrosion resistance than AZ91D and plasma-sprayed Al-Si coating. The decreasing order of the corrosion rates are AZ91D base metal, sprayed Al-Si coating and laser-remelted Al-Si coating. The fine Al-Si eutectic matrix in the laser-remelted microstructure contributed to the improved corrosion performance relative to the AZ91D and the plasma-sprayed coating. The predominant corrosion mechanisms in AZ91D, plasma-sprayed coating and laser-remelted coating are intra-granular corrosion, crevice corrosion and the combined pitting and galvanic corrosion, respectively.     

AZ91D镁合金微弧氧化膜在不同浓度NaCl溶液中的腐蚀行为(英文)

采用微弧氧化技术(MAO)在镁合金 AZ91D 表面制备微弧氧化陶瓷膜。利用电化学技术和浸泡实验研究该镁合金试样在不同浓度(0.1%,0.5%,1.0%,3.5%和 5.0%,质量分数) NaCl 溶液中的腐蚀行为。结果表明,试样的腐蚀速率随着氯离子浓度的升高而增大。在较高浓度(1.0%,3.5%和 5.0%)的 NaCl 溶液中的主要腐蚀形式是点蚀,而在较低浓度(0.1%和 0.5%)中是全面腐蚀。腐蚀过程可以分为两个阶段:亚稳态蚀点的出现和蚀点的生长。根据腐蚀过程中阻抗谱的特点,对镁合金微弧氧化膜试样在不同浓度 NaCl 溶液中浸泡 120 h 提出了不同的等效电路来模拟其腐蚀行为。     

Corrosion and wear properties of electroless Ni-P plating layer on AZ91D magnesium alloy

A direct electroless Ni-P plating treatment was applied to AZ91D magnesium alloy for improving its corrosion resistance and wear resistance. Corrosion resistance of the Ni-P coatings was evaluated by potentiodynamic polarization and immersing experiments in 3.5% NaCl solution. The wear resistance of the coatings was investigated by the wear track and the mass change after ball-on-disk experiment. The results show that corrosion resistance and wear resistance of the AZ91D alloy are greatly improved after direct electroless Ni-P plating. No discoloration is noticed until 4 d of immersion in 3.5% NaC1 solution. Potentiodynamic polarization experiments show that the free corrosion potential of magnesium alloy is shifted from -1 500 mV to -250 mV and passivation occurs at 1 350 mV after direct electroless plating. The friction coefficients and wear rates of Ni-P coating and Ni-P coating after tempering are 0.10-0.351, 9.038×10^-3 mm^3/m and 0.13-0.177, 3.056×10^-4 mm^3/m, respectively, at a load of 1.5 N with dry sliding. Although minor hurt on corrosion resistance was caused, significant improvement of wear resistance was obtained after tempering treatment of the coating.     

Al_2O_3-SiO_2/AZ91D镁基复合材料的挤压浸渗制备工艺及微观组织和界面的研究

采用挤压浸渗法制备Al_2Or_3-SiO_2/AZ91D复合材料.改进制备工艺,利用价格低廉且来源广泛的硅酸铝短纤维作增强体,用磷酸铝作黏结剂制得预制体.在预制体温度660℃、模具温度560℃、浇注温度760℃和压力30～50MPa下,通过挤压浸渗工艺制备AZ91D镁基复合材料.采用光学显微分析、XRD衍射分析、SEM扫描分析等方法研究该复合材料.结果表明,镁与磷酸铝黏结剂反应后在界面上生成一定数量的Mgo颗粒和少量的MgAl_2O_4颗粒,致使硅酸铝增强纤维和镁合金基体之间形成较强界面结合.复合材料组织致密、无明显孔洞及夹杂等铸造缺陷.其界面上的反应产物主要有MgO、MgP_4、MgAl_2O_4和Mg_2Si