关键词： AZ系镁合金   Al-Mn相   氧化物夹杂   分布   形成机理  

摘要： 以AZ系镁合金(AZ31、AZ80和AZ91)中的Al-Mn相作为研究对象,利用OM、SEM和EPMA等方法研究Al-Mn相在AZ系镁合金中的分布和形成,讨论Al-Mn相在晶内、晶界及氧化物夹杂处的组成,及Al-Mn相在氧化物夹杂处析出机理。结果表明:AZ系镁合金中的Al-Mn相主要为颗粒状、棒状和不规则块状,尺寸均小于30μm,主要分布在初生α-Mg、β-Mg_(l7)Al_(12)相和晶界处,呈弥散分布形态;Al-Mn相为Al_8Mn_5或Al_8(Mn,Fe)_5。AZ系合金中的氧化物夹杂MgO能够诱发Al8Mn5相在其周围以聚集分布的形式析出;通过分析Al_8Mn_5相在MgO夹杂处形成、富集机理,获得Al_8Mn_5相在AZ系镁合金中MgO夹杂处形核长大的析出模式。

关键词： 高强镁合金   浇注温度   压射速度   压射比压   力学性能  

摘要： 采用不同的浇注温度、压射速度和压射比压对汽车用新型高强Mg-8Gd-4Y-0.3Zr-0.3Ti镁合金试样进行了制备并对力学性能进行了测试和分析。结果表明:与650℃浇注温度相比,710℃浇注温度下的抗拉强度和屈服强度分别增大了31、27 MPa;与100 m/min压射速度相比,200 m/min压射速度下的抗拉强度和屈服强度分别增大了22、16MPa;与50 MPa压射比压相比,90 MPa压射比压下的抗拉强度和屈服强度分别增大了26、24 MPa;伸长率变化幅度较小。Mg-8Gd-4Y-0.3Zr-0.3Ti镁合金的压铸工艺参数优选为:710℃浇注温度、200 m/min压射速度、90 MPa压射比压。

关键词： 稀土镁合金   往复镦挤   织构  

摘要： 采用往复镦挤(RUE)工艺可以对合金进行剧烈塑性变形。应用降温RUE工艺对Mg-12.0Gd-4.5Y-2.0Zn-0.4Zr(wt%)合金进行不同道次的变形和热处理,对比分析了其微观组织、织构及力学性能的演变。结果发现:随着变形道次的增加,合金粗大晶粒减少,动态再结晶晶粒数量分数升高,动态再结晶晶粒对原始晶粒的吞噬作用促进了晶粒的连续细化,组织均匀性大大改善。同时合金(0001)基面织构最大极密度值随着加工道次的增加显著下降,动态再结晶晶粒取向随机分布,促进了基面织构弱化。由于组织细化和织构减弱,合金的室温抗拉强度及屈服强度均明显升高,在3道次变形和热处理后材料的力学性能达到最高。

关键词： 海藻酸钠   磷虾蛋白   低温诱导相分离   支架材料   生物相容性   医用纺织品  

摘要： 为提高海藻酸钠基支架材料的强度和生物相容性,以海藻酸钠(SA)和磷虾蛋白(AKP)构成聚电解质复合体系,通过低温诱导相分离-化学交联法制备SA/AKP支架材料,比较不同质量分数SA/AKP溶液制备的支架材料的结构形态、力学性能、孔隙率、透气性、吸水性及生物相容性。结果表明:在SA/AKP溶液质量分数为4%时,支架孔径在20~96μm之间,孔径大小均一,形状规整;支架材料的孔隙率、透气性、液体吸收性随SA/AKP溶液质量分数增加而降低,断裂强度和断裂伸长率随SA/AKP溶液质量分数增加而增加,在质量分数为4%时,支架材料的孔隙率为86.4%,透气率为58.9%,且具有较高的强度与伸长;支架材料的细胞毒性等级为0级,具有优异的生物安全性。

关键词： Magnesium alloy   Dynamic   Corrosion behavior   EIS   Simulated body fluid  

摘要： Two specimens were prepared along the normal (ND) and transverse (TD) directions of the AZ80 magnesium alloy rolled sheet, respectively, and the other specimen was prepared along the normal direction at 45 degrees (ND45). Three specimens (ND, ND45 and TD) were immersed in dynamic immersion equipment for in-situ electrochemical test. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to investigate the static and dynamic corrosion behavior of the specimens in simulated body fluid (SBF). The results indicated that the specimens with different orientations exhibited anisotropy of corrosion performance. The electrochemical corrosion resistance of the specimens decreased in the following order: TD > ND45 > ND. The electrochemical corrosion resistance of the specimens decreased with increasing flow rate. The specimens immersed in SBF solution suffered localized corrosion, and the corrosion degree at the edge position of the specimen was higher than that at the middle position in dynamic environment. Computational fluid dynamics (CFD) simulations showed that with the increase of flow rate, the increase of shear stress and mass transfer coefficient led to the intensification of localized corrosion. The effect of initial texture and flow rate on the corrosion behavior of magnesium alloy was discussed.

关键词： AZ80   EBSD   晶界   取向差   几何必须位错密度  

摘要： 利用电子背散射衍射(EBSD)技术观察研究了不同状态条件下AZ80镁合金的微观组织,分析了不同状态条件下AZ80镁合金的微观组织演化。结果表明:按照铸态、均质化热处理态和塑性变形态顺序,试样平均晶粒尺寸逐渐减小,平均晶粒形状纵横比呈先增大后减小的变化趋势,网状β-Mg_(17)Al_(12)相逐渐消失,材料塑性和强度得到提高;晶界的协调作用主要受晶界迁移与几何必须位错(GND)密度两方面的影响,伴随晶界的迁移,小角度晶界逐渐增多并阻碍再结晶的进行,使再结晶区呈先增大后减小的变化趋势,而亚结构区则逐渐减小,亚结构区的消失为孪晶的形成提供了能量,促进了孪晶的形成;几何必须位错密度呈先减小后增大的变化趋势,几何必须位错密度的减小促进了孪晶的生长和晶粒间的旋转移动,而几何必须位错密度的增大则使孪晶的生长和晶粒间的旋转移动受到阻碍。塑性变形态镁合金出现了典型的基面织构。

关键词： 镁合金   镁基复合材料   制备工艺   增强相  

摘要： 镁基复合材料是继铝基复合材料后的又一具有竞争力的轻金属基复合材料.综述了近些年来制备镁基复合材料的常用方法及特点,并对镁基复合材料常用增强相进行了概述,对镁基复合材料的发展进行了展望.

关键词： ZK60   pH   Crack growth   Pit   Hydrogen embrittlement  

摘要： To investigate the effect of pH on corrosion and fatigue crack growth of ZK60 magnesium alloy, the corrosion and fatigue crack growth experiments with cyclic sinusoidal waveform in PBS with pH 5.2, 7.4 and 9.0 were performed. With the increase of pH, the integrity and compactness of the protective layer increased as well as Mg-3(PO4)(2), reducing the channels for Cl- and hydrogen to contact the magnesium matrix which inhibited pitting and crack growth rate in LI stage. In LII stage, the effect of pH was weakened and the slope of crack propagation curve decreased.

关键词： Bilayer coating   Corrosion   Bionic superhydrophobic surface  

摘要： A superhydrophobic bilayer surface was created with a contact angle (CA) of 157.3 +/- 1 degrees and sliding angle (SA) of 2 degrees +/- 0.5 degrees using a simple one-step solvothermal process. The bionic micro/nano structures are similar to the flower of a carnation and common sowthistle, which plays an important role in resisting corrosion. In addition, potentiodynamic polarization shows that the superhydrophobic bilayer surface has excellent corrosion resistance. This preparation is beneficial as it is simple to fabricate, low cost, is easily prepared across large areas, and has excellent corrosion resistance, amongst other benefits. It can effectively broaden the application of magnesium alloys and extend to other conductive metal materials.

关键词： Friction stir welding   Intermetallic compounds   Aluminium alloy   Magnesium alloy   Ultrasonic vibration  

摘要： The formation of intermetallic compounds (IMCs) in friction stir welding of Al and Mg alloys worsens the strength and toughness of dissimilar joints. Understanding of the morphology and thickness variation of IMCs at different locations inside the weld will lay solid foundation for mitigating the unfavorable effects of IMCs. In this study, friction stir welding tests of Al/Mg alloys with and without exertion of ultrasonic vibration were performed, and the distribution of IMCs at transverse and horizontal cross-sections of welds were observed and characterized at more checking points. The results show that as the depth distance from the top surface of weld gets larger, the thickness of IMCs on transverse cross-section increases first and then decreases, and reaches the maximum value at a depth of about 1 mm. On the horizontal plane at upper part of weld, the thickness of IMCs first increases and then decreases as the distance gets farther from the center of the exit hole, and reaches a stable stage outside of the range covered by the shoulder. The application of ultrasonic vibration can reduce the thickness of IMCs in the whole weld, and make the peak value of IMCs thickness appear at a location nearer the exit hole on horizontal planes at both upper and lower parts of weld.