Improved Corrosion Behavior of Biodegradable Mg-4Zn-1Mn Alloy Modified by Sr/F co-doped CaP Micro-arc Oxidation Coatings

The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.

热挤压高强度Mg-6Zn-4Y合金(英文)

通过铸造和300℃热加压制备细晶Mg-6Zn-4Y合金,利用XRD、OM、SEM和TEM研究合金组织,并测试其室温拉伸性能。结果表明,合金主要由α-Mg和W相两相组成,挤压态合金具有双峰晶粒尺寸分布;细小晶粒为动态再结晶晶粒,平均尺寸为1.2μm;粗大晶粒(占面积分数的23%)为未再结晶区域,并沿挤压方向被拉长。合金的极限抗拉强度、屈服强度和伸长率分别为(371±10)MPa,(350±5)MPa和(7±2)%,其工程应力—应变曲线有明显的屈服点。合金高强度归因于晶粒细化和W相、纳米沉淀颗粒及强基面织构的增强作用。

Effects of heat treatment on microstructure and mechanical properties of Mg-6Zn-4Sm-0.4Zr alloy

A new rare earth magnesium alloy(Mg-6 Zn-4 Sm-0.4 Zr, wt.%) was prepared by permanent mould casting. The microstructure and mechanical properties of the alloy sample in as-cast and various heat treatment situations were characterized with an optical microscope(OM), X-ray diffractometer(XRD), scanning electron microscope(SEM) equipped with energy dispersive spectroscope(EDS), transmission electron microscope(TEM) and mechanical tests at room temperature, respectively. The experimental results show that the as-cast alloy mainly consists of α-Mg, eutectic Mg_2Zn_3, MgZnSm and Mg_(41)Sm_5. These eutectic phases with continuous or semicontinuous morphology principally distribute along grain boundaries. Almost all the eutectic compounds dissolve in α-Mg and the grains have no obvious growth trend after optimum solution treatment at 490 °C for 18 h. Meanwhile, the ultimate tensile strength(UTS) of 229 MPa and elongation(EL) to rupture of 9.78% can be achieved through the optimal solution treatment, which increase by 37 MPa and 57.74%, respectively, compared with that of the as-cast alloy. Further aging treatments at 200 °C for different durations lead to the conspicuous increment of mechanical properties and prominent age-hardening response. Peak-aged alloy(treated at 200 °C for 12 h) reveals better mechanical properties(UTS 258 MPa, EL 9.42%, hardness 73.4 HV) compared with the same alloy treated in other aging conditions, which is mainly ascribed to precipitated Mg_2Zn_3 and MgZn_2 phases. Fracture analysis demonstrates that the as-cast alloy belongs to inter-granular and cleavage fracture patterns, while the solutionized alloy(treated at 490 °C for 18 h) reveals trans-granular and quasi-cleavage fracture modes. For the peak-aged alloy, the fracture pattern obeys the mixture of trans-granular and cleavage modes.

Effect of ultrasonic melt treatment on degassing of Mg-6Zn-1Ca alloy

The effect of ultrasonic power and treatment time on degassing of Mg-6Zn-1Ca alloy was studied in this paper. The degassing effect was characterized by measuring densities of ingots. The results show that proper ultrasonic treatment can remove hydrogen from the melt of the Mg-6Zn-1Ca alloy. The ultrasonic degassing effect is closely related to the ultrasonic power density and treatment time. The degassing efficiency increases with an increase in ultrasonic power density when the melt is treated at 690 °C for 120 s, reaching its highest value at 1.2 W·cm-3. When the power density is 1.2 W·cm-3, with an increase in ultrasonic treatment time, the degassing efficiency increases at first, reaches its peak value at 120 s, then decreases as the ultrasonic treatment is further prolonged. In this experiment, the optimum degassing effect with an efficiency of 67.5 % is obtained by ultrasonic treatment with the power density of 1.2 W·cm-3 for 120 s. The maximum density of ingot can be increased from 1.8069 g·cm-3 to 1.8146 g·cm-3(increased by 0.43%).

挤压态和热处理态Mg-6Zn-1Mn-4Sn-1.5Nd镁合金的显微组织和力学性能（英文）

利用光学显微镜、X射线衍射仪、扫描电镜、电子背散射衍射、透射电镜、硬度以及力学性能测试等对挤压态和T5处理态的Mg-6Zn-1Mn-4Sn-1.5Nd镁合金的显微组织和力学性能进行研究。研究结果表明:合金铸态的相组成为α(Mg)、Mn、Mg7Zn3、Mg2Sn和MgS nN d相。挤压过程中完成动态再结晶,再结晶晶粒的平均尺寸为7.2μm。T5热处理显著提高挤压态合金的强度。合金的屈服强度和抗拉强度分别增加94 MPa和34 MPa。显微组织分析表明,合金强度的提高主要是由于时效过程中析出高密度的β′1杆状相。

Mg-4Zn-3Y合金高温阻燃特性

为了改善镁合金在熔铸及加工过程中抗氧化燃烧性能,用合金化阻燃方法在Mg-4Zn合金中添加适宜的Y元素制备了阻燃效果优异的Mg-4Zn-3Y合金.采用俄歇电子能谱仪、X射线衍射仪和扫描电镜(SEM+EDS)研究了氧化膜的显微形貌、合金元素分布及其物相组成.结果表明,Mg-4Zn-3Y合金在高温下暴露于大气中时,燃点提高250℃,合金表面生成一层以Y2O3为主的氧化膜,改善镁合金氧化膜的粘附性,提高高温抗氧化和燃烧能力.基于高温氧化热力学分析,建立了Mg-4Zn-3Y合金在高温下的氧化物理模型.Mg-4Zn-3Y合金能在1065K时于大气中保温30min而不燃烧,实现了低Y元素含量镁合金在大气条件下的无保护熔炼.

Mg-6Al-1Zn-1.8Gd-0.9Y镁合金的高温蠕变行为

研究了Mg-6Al-1Zn-1.8Gd-0.9Y镁合金的高温蠕变行为。结果表明:Mg-6Al-1Zn-1.8Gd-0.9Y合金在50MPa、150℃的蠕变量为0.86%,稳态蠕变速率为1.8×10^(-8) s^(-1);经热处理后的合金在50MPa、150℃的蠕变量为0.36%,稳态蠕变速率为8.9×10^(-9)s^(-1),基本可满足高温下的使用要求。铸态合金在50MPa下的蠕变激活能为24.3kJ/mol,热处理后的合金在50、70MPa下的蠕变激活能分别为23.4、34.3 kJ/mol,这与晶界滑移激活能接近。

稀土Y对Mg-6Zn-1Mn合金显微组织和力学性能的影响

利用光学显微镜、X射线衍射仪、扫描电子显微镜、万能力学试验机等手段,系统研究了不同含量Y（1%-6%（质量分数））对Mg-6Zn-1Mn合金显微组织和力学性能的影响。结果表明,随着Y的不断增加,Mg-6Zn-1Mn系铸态合金主要物相演变规律为α-Mg＋Mg7Zn3→α-Mg＋I→α-Mg＋W→α-Mg＋X,这主要归因于不同的Zn/Y原子比。研究发现,当Y含量低于2%时,挤压可使晶界和晶粒内部析出细小弥散的第二相,同时提高了合金强度和室温延展性。而随着Y的进一步增加,第二相颗粒变大,且主要存在于晶界,热挤压过程中晶粒不易被挤碎,弱化了析出相与基体的界面能,最终使得挤压态合金综合力学性能降低。

超声处理功率对Mg-6Zn-0.5Y合金显微组织及力学性能的影响

对Mg-6Zn-0.5Y合金熔体进行功率分别为0,300,600,900 W连续超声处理。通过金相显微镜、X射线衍射仪、扫描电镜等分析手段研究了超声处理功率对其显微组织及力学性能的影响。结果表明,经600 W超声处理的Mg-6Zn-0.5Y合金组织细化效果最好,初生α-Mg相由粗大的树枝晶变为细小的球状等轴晶,准晶I相由粗大的半连续网状分布变成断续的细线状分布。此外,力学性能分析显示,当超声处理功率为600 W时,Mg-6Zn-0.5Y合金的抗拉强度和伸长率均达到最大值,比未处理时分别提高了67%和56%。

快速凝固Mg-6Zn-1Y-1Ce合金的TEM组织(英文)

利用单辊甩带技术制备快速凝固Mg-6Zn-1Y-1Ce薄带,并利用透射电子显微镜和能谱仪分析薄带组织。结果表明:薄带近辊面区域晶粒内部和晶界处分布着高密度颗粒,颗粒密度在中间区域和自由面区域有所降低;快速凝固合金主要由过饱和的--Mg固溶体、T相和W相组成,同时还存在少量的二十面体准晶相颗粒和Mg4Zn7相颗粒;其中T相为体心正交晶体结构,是由于体心正方结构的Mg12Ce相中部分Mg原子被Zn原子代替而形成的。

严酷变形Mg-6Zn-1Y合金组织

利用正挤压和往复挤压-正挤压联合工艺制备细晶Mg-6Zn-1Y合金,研究挤压工艺对合金组织的影响。结果表明:挤压比为11.3时,300、340℃正挤压合金晶粒平均尺寸分别为2.7、12.9μm;300℃时再结晶机制为非连续动态再结晶机制,组织不均匀;340℃时为连续动态再结晶机理,组织均匀;挤压比6.1时,300℃挤压合金平均晶粒尺寸为3.2μm。降低挤压温度和增大挤压速率均可以提高组织细化程度。340℃往复挤压5道次后再经255℃正挤压合金组织均匀,平均晶粒尺寸为5.3μm,均匀的细晶组织归因于在往复挤压和正挤压过程中发生了2次动态再结晶。

热处理对Mg-8Li-4Zn-3Y合金组织和性能的影响

采用锂盐熔剂保护法熔铸Mg-8Li-4Zn-3Y合金,并对合金进行T4固溶和T6固溶+时效热处理,探讨了热处理对Mg-8Li-4Zn-3Y合金组织及硬度的影响。结果表明,T4固溶后,组织中的强化相减少,α-Mg相晶粒尺寸增大,形貌亦变得不规则,合金的硬度下降;再经过T5时效后,组织中又析出一些强化相颗粒,合金的硬度有一定程度的提高。压缩过程中,Mg-8Li-4Zn-3Y合金试样均呈鼓形后开裂,且均呈45°的剪切断裂。

Mg-13Gd-4Y-2Zn-0.5Zr镁合金减振性能的研究

采用TA Q800 DMA对Mg-13Gd-4Y-2Zn-0.5Zr镁合金进行阻尼性能测试,并通过阻尼-应变、应力-应变曲线的拟合公式计算出减振系数。结果表明：不同热处理工艺对合金的减振性能有一定的影响。热变形、热处理对合金内的析出相有调控作用,进而影响合金的阻尼性能。高应变区域,变形＋T6态合金内的析出相最小,数量最多,其阻尼性能最差。合金的屈服强度对减振系数有较大影响,变形＋T6态合金的减振系数较高,变形态次之,铸态合金的最小。

熔铸工艺条件对Mg-6Zn-0.5Y合金铸锭密度的影响

试验研究了熔体温度、保温时间、冷却速度和C2Cl6除气剂添加量对Mg-6Zn-0.5Y合金铸锭密度的影响。结果表明:RPT(减压凝固法)铸锭密度随着熔体温度升高而降低,这表明氢含量随着温度的升高而增加;在相同的保温温度下,随着熔体保温时间延长,RPT铸锭密度逐渐降低,这表明氢含量随保温时间的延长而缓慢增加;在相同熔体温度下,随着熔体凝固冷却速度增加,铸锭密度逐渐增加;当熔体在720℃下分别添加占熔体质量的1%、3%和5%的C2Cl6除气剂处理时,铸锭的密度均比未处理的铸锭密度大,当C2Cl6用量为3%时,铸锭密度达到最大值,从1.8649 g/cm3增加到1.877 4 g/cm3,表明具有最佳的除氢效果。

挤压铸造压力对Mg-4Zn-1.2Y合金组织及力学性能的影响

采用显微组织观察、拉伸试验、密度测试等研究了不同挤压铸造压力对Mg-4Zn-1.2Y合金显微组织与力学性能的影响。结果表明:随着挤压压力的增加,Mg-4Zn-1.2Y合金的平均晶粒尺寸和第二相体积分数逐渐减小,挤压压力从0增加到150 MPa时,合金晶粒细化明显,挤压压力超过150 MPa后,合金晶粒细化趋势变缓。随着挤压压力的增加,Mg-4Zn-1.2Y合金的抗拉强度、屈服强度、伸长率及密度均逐渐增加。与挤压压力为0 MPa的合金相比,挤压压力150 MPa的合金抗拉强度、屈服强度和伸长率分别提高了24.4%、23.3%和72.7%,力学性能显著提高,挤压压力超过150 MPa后,合金力学性能提高幅度变缓。

(Y,Gd)H_(2) phase formation in as-cast Mg-6Gd-3Y-0.5Zr alloy

In this work,a new(Y,Gd)H_(2) precipitate was identified and systematically investigated in the as-cast Mg-6Gd-3Y-0.5Zr alloy by XRD,SEM with EDS,TEM with EDS techniques and thermodynamics analysis.Results show that the as-cast alloy contains α-Mg,Mg_(24)(Gd,Y)_(5),and(Y,Gd)H_(2) phase.The(Y,Gd)H_(2) phase usually forms near the eutectic phase Mg_(24)(Gd,Y)_(5) or in the α-Mg grains,displaying a rectangle-shape.The Mg_(24)(Gd,Y)_(5) and(Y,Gd)H_(2) phases crystalize in bcc and fcc structure,respectively,and the(Y,Gd)H_(2) phase has a semi-coherent relationship with α-Mg matrix.The thermodynamics calculation results reveal that the hydrogen dissolved in the melt leads to the formation of hydrides.It is also found that the(Y,Gd)H_(2) hydride can form directly from the liquid phase during solidification.Additionally,it can precipitate by the decomposition of Mg_(24)(Gd,Y)_(5) phase due to absorbing hydrogen from the remaining melt.

Mg-8Zn-4Al-1Ca合金的时效微观组织(英文)

利用TEM和HRTEM研究Mg-8Zn-4Al-1Ca合金的时效微观组织。结果表明:Mg-8Zn-4Al-1Ca合金较Mg-8Zn-4A1合金时效硬度显著增高。Mg-8Zn-4Al-1Ca合金在160°C时效16 h,有大量的盘状Ca2Mg6Zn3相沉淀弥散析出,此外,合金的微观组织中还存在晶格畸变、蜂窝状的莫尔条纹、刃型位错及位错环;经48 h时效后合金中沉淀相为粗大的盘状沉淀相和细小、弥散的粒状沉淀相;经227 h时时效后后,其组织中存在大量MgZn2相和Ca2Mg6Zn3相。因此,在Mg-8Zn-4Al-1Ca时效160°C的合金中添加Ca元素能有效提高合金的时效硬度及促进MgZn2强化相的生成。

挤压温度对Mg-6Zn-1Mn-4Sn-0.5Y镁合金组织和性能的影响（英文）

通过光学显微镜(OM),X射线衍射(XRD),扫描电子显微镜(SEM),电子背散射衍射(EBSD)以及拉伸试验对360和420℃挤压的Mg-6Zn-1Mn-4Sn-0.5Y变形镁合金的组织和性能进行了研究。结果表明,合金铸态和时效态的相组成为α-Mg,Mn,Mg_7Zn_3,Mg_2Sn,和MgSnY相。挤压温度从360℃增加到420℃,动态再结晶完成,晶粒长大,合金的屈服强度、抗拉强度以及延伸率分别由259 MPa,350 MPa和18.3%降低至239 MPa,332 MPa和12.5%。理论计算和拉伸试验结果表明,细晶强化和固溶强化对合金屈服强度的增加产生决定性影响。

流变挤压铸造Mg-6Zn-3RE-1.4Y镁合金的组织

采用超声振动制备了Mg-6Zn-3RE-1.4Y新型镁合金的半固态浆料,并对半固态浆料进行直接挤压铸造。研究了流变挤压铸造Mg-6Zn-3RE-1.4Y镁合金的组织和相组成。结果表明,Mg-6Zn-3RE-1.4Y合金流变挤压铸件组织中存在两种细小圆整但尺寸差异较大的α1-Mg和α2-Mg晶粒,α1-Mg平均晶粒尺寸和形状系数分别为22μm和0.74,α2-Mg为浆料中剩余液相形成的以球形为主的细小晶粒。合金的相组成主要为α-Mg基体、α-Zr以及沿晶界分布的Mg12Ce、Mg12La以及I-Mg3Zn6Y相。