变形态Mg-Nd合金的组织转变和拉伸性能特征

研究不同变形条件对Mg-2.2Nd-0.5Zn-0.5Zr合金室温拉伸性能和组织的影响.经过不同条件的热挤压变形后,该合金的强度和延性都有不同程度的增加,屈强比从0.58提高到0.87左右.固定变形温度时,强度随变形速率增大而降低,延性反之.固定变形速率时,升高变形温度则强度降低,延性增加.弥散于晶界的Mg9Nd化合物细化了晶粒.变形态Mg-Nd合金的高温超塑拉伸研究发现,375℃是该合金的最佳超塑变形温度,应变速率在1×10-2s-1时,延伸率达到329%;当变形速率提高到2×10-2s-1时,该合金的延伸率仍可达到213%.分析不同真应变下的组织发现,在变形初期发生动态再结晶,晶粒得到破碎而变得细小,随着变形程度的增加,晶粒长大程度较小.在变形后的断口形貌中发现,Mg-Nd合金的超塑变形机制为晶界滑移控制下的孔洞连接协调机制.     

A novel white afterglow phosphorescent phosphor Ca3SnSi2O9: Dy

AZ91 alloy powder with 2 mass% Si addition (flakes) was obtained by two-roller quenching equipment with an atomized accessory. The powders were consolidated and extruded into bar. The microstructures of the powders (flakes) and bars were characterized by optical microscope (OM), XRD, TEM and SEM. The results showed that the grain size of the powder were dendritic with the sizes of about 1–5 μm. The as-extruded alloy bars retain equiaxed grains with a large number of precipitated phases, i.e. Mg₂Si, β-Al₁₂Mg₁₇ and AlMg₂Zn. The alloy exhibits excellent mechanical properties. The 0.2% yield tensile strength, ultimate tensile strength and elongation of rupture were 322.47, 429.78 MPa and 6.4%, respectively. The as-extruded alloy bars show preferable elevated temperature mechanical properties.     

热处理对挤压镁合金AZ91和ZK60组织与性能的影响

通过力学性能测定以及金相显微组织观察,对挤压态AZ91和ZK60镁合金的热处理工艺进行了研究。结果表明,AZ91合金固溶态与挤压态相比抗拉强度变化不大,但伸长率有较大幅度的提高;时效硬度峰值时的抗拉强度与固溶态相比有一定的提高,但伸长率有较大幅度的降低。ZK60合金固溶态与挤压态相比抗拉强度和伸长率均有相当程度地降低,且时效硬度峰值时的抗拉强度与同溶态相比有一定的提高,伸长率也有较大幅度的降低。AZ91合金固溶处理后晶粒尺寸与挤压态相比有所增大,但ZK60合金固溶处理后晶粒尺寸显著粗化。同时,两种合金固溶时效处理后伴有强化相粒子析出。     

热处理对挤压镁合金AZ91拉伸变形与断裂行为的影响

通过金相显微组织观察和断口SEM分析，研究了热处理对挤压AZ91镁合金拉伸变形与断裂行为的影响。结果表明：AZ91镁合金固溶态与挤压态相比抗拉强度变化不大，但伸长率有较大幅度的提高，品粒尺寸有所增大；时效峰值态的抗拉强度与固溶态相比有一定的提高，但伸长率有较大幅度的降低，合金固溶时效处理后伴有强化相粒子析出。AZ91合金挤压态和固溶态的断面都有韧窝特征，为微孔形核的韧性断裂机制，而在时效峰值态的断面上则呈现出了韧性与脆性混合断裂的特征。     

热处理对挤压镁合金AZ91拉伸变形与断裂行为的影响

通过金相显微组织观察和断口SEM分析,研究了热处理对挤压AZ91镁合金拉伸变形与断裂行为的影响。结果表明:AZ91镁合金固溶态与挤压态相比抗拉强度变化不大,但伸长率有较大幅度的提高,晶粒尺寸有所增大;时效峰值态的抗拉强度与固溶态相比有一定的提高,但伸长率有较大幅度的降低,合金固溶时效处理后伴有强化相粒子析出。AZ91合金挤压态和固溶态的断面都有韧窝特征,为微孔形核的韧性断裂机制,而在时效峰值态的断面上则呈现出了韧性与脆性混合断裂的特征。     

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AZ91D EXTRUDED TUBE

The effect of extrusion ratio on microstruetures and mechanical properties of magnesium alloy AZ91D extruded tube at 430℃ has been studied. After the evolution of microstracture and mechanical properties of AZ91D during extrusion were studied, the following parameters were obtained： tensile strength reached the climax value of 306.9MPa and elongation peak value of 10.1% at an extrusion ratio of 7.125, and with the increase of the extrusion ratio to 7.45, yield strength reached a top value of 285.795MPa with decreased tensile strength and elongation. It was concluded that mechanical properties of magnesium alloys AZ91D could be enhanced by adjusting the extrusion ratio near recrystallization.     

7075铝合金对AZ91镁合金组织和性能的影响

为了研究7075铝合金对AZ91镁合金组织与性能的影响,采用光学显微镜、扫描电镜、X 射线衍射仪、万能材料试验机研究了AZ91镁合金的显微组织与力学性能。结果表明：向AZ91镁合金中加入7075铝合金可使该合金的铸态组织明显细化,当7075铝合金含量超过4%（质量分数,下同）时,AZ91镁合金铸态组织中Mg17Al12相数量明显减少,并且组织中生成了Al6Mn新相。合金抗拉强度与延伸率随着7075铝合金加入量的增加而提高,当7075铝合金的加入达到4%,其抗拉强度与延伸率达到最大值,分别为186 MPa和8.2%     

SiC_p/AZ91镁基复合材料的热挤压

采用搅拌铸造法制备SiC体积分数为5%、10%和15%的颗粒增强AZ91镁基复合材料（SiCp/AZ91）。复合材料经过T4处理后,于350°C以固定挤压比12：1进行热挤压。在铸态复合材料中,颗粒在晶间微观区域发生偏聚。热挤压基本上消除了这种偏聚并有效地改善颗粒分布。另外,热挤压有效地细化基体的晶粒。结果表明：热挤压明显提高复合材料的力学性能。在挤压态复合材料中,随着SiC颗粒含量的升高,基体的晶粒尺寸减小,强度和弹性模量升高,但是伸长率降低。     

稀土铈对AZ61变形镁合金组织和力学性能的影响

研究了不同稀土铈含量对AZ61合金显微组织和力学性能的影响.实验发现:加入稀土铈后,AZ61合金铸态组织的β相变少、变细,铸态晶粒细化;大部分铈与铝结合生成高熔点、高热稳定性的稀土相Al4Ce;在热挤压和退火过程中,Al4Ce能够阻碍晶粒或亚晶粒的长大,使晶粒细化.适量的稀土铈提高了挤压态合金的强度、延伸率和显微硬度;而过量的稀土铈则会导致AZ61合金的性能下降;含1.0%稀土铈的挤压态合金可得到最高的抗拉强度308.1MPa、最高屈服强度180.1MPa、最大的显微硬度HV80.5和最高的延伸率14.2%;所有试验合金的断裂方式是解理断裂.     

Effect of extrusion processing parameters on microstructure and mechanical properties of as-extruded AZ31 sheets

The AZ31 sheets were prepared by extrusion.The effects of the extrusion processing parameters including the temperature extrusion ratio,and structure of the extrusion die on the microstructure and mechanical properties of the as-extruded AZ31 sheets were investigated.The results show that the partial grains grow abnormally.and the mechanical and anisotropic properties of the as-extruded AZ31 sheets have little change at the extrusion temperatures of 380-400℃and the extrusion ratio of 13.3.With the increa...     

挤压速度和电磁铸造锭坯对AZ31镁合金板材组织和性能影响

文章研究挤压条件下挤压速度和电磁铸造锭坯对挤压态AZ31镁合金板材组织和性能的影响。研究结果发现,挤压速度比较低时,板材晶粒尺寸小,板材的表面质量比较好;随着挤压速度的降低,抗拉强度、屈服强度和延伸率都有一定的提高。由于镁合金是HCP的晶体结构,同时对挤压速度非常敏感,对变形均匀性影响比较大,因此造成挤压板材的内外晶粒大小不均。在电磁场的作用下,溶质在晶内的固溶度增大,同时晶粒大小也比常规铸造的细小,因此电磁铸造的锭坯经挤压机挤压后,挤压板材的晶粒尺寸比较细小,且强度和塑性都有所提高。     

Processing, microstructure and mechanical properties of magnesium matrix nanocomposites fabricated by semisolid stirring assisted ultrasonic vibration

Particulate reinforced magnesium matrix nanocomposites were fabricated by semisolid stirring assisted ultrasonic vibration. Compared with the as-cast AZ91 alloy, the grain size of matrix alloy in the SiCp/AZ91 nanocomposite stirring for 5 min was significantly decreased due to the addition of SiC nanoparticles. SiC nanoparticles within the grains exhibited homogeneous distribution although some SiC clusters still existed along the grain boundaries in the SiCp/AZ91 nanocomposite stirring for 5 min. With increasing the stirring time, agglomerates of SiC nanoparticles located along the grain boundaries increased. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite stirring for 5 min were simultaneously improved compared with the as-cast AZ91 alloy. However, the ultimate tensile strength and elongation to fracture of the SiCp/AZ91 nanocomposite decreased with increasing the stirring time.     

Nd对压铸AZ91D合金组织与性能的影响

传统压铸获得AZ91D和AZ91D-1.11Nd两种合金试样,采用光学金相显微镜、扫描电子显微镜和X射线衍射仪分析了压铸态微观组织和相组成,并测试了其拉伸力学性能、硬度、导热性能和流动性能.结果 表明,在AZ91D合金中添加1.11％Nd后,压铸态晶粒有所细化,形成较多弥散分布的细小颗粒状Al2Nd和少量针状Al11N...     

Fabrication of carbon nanotubes reinforced AZ91D composites by ultrasonic processing

Magnesium matrix nanocomposite reinforced with carbon nanotubes （CNTs/AZ91D） was fabricated by mechanical stirring and high intensity ultrasonic dispersion processing. The microstructures and mechanical properties of the nanocomposite were investigated. The results show that CNTs are well dispersed in the matrix and combined with the matrix very well. As compared with AZ91D magnesium alloy matrix, the tensile strength, yield strength and elongation of the 1.5%CNTs/AZ91D nanocomposite are improved by 22%, 21% and 42% respectively in permanent mold casting. The strength and ductility of the nanocomposite are improved simultaneously. The tensile fracture analysis shows that the damage mechanism of nanocomposite is still brittle fracture. But the CNTs can prevent the local crack propagation to some extent.     

Grain-Refined AZ92 Alloy with Superior Strength and Ductility

Grain-refined AZ92 (GR-AZ92) alloy with superior tensile properties is developed by adding 1 wt% Zn and a very small amount of SiC (0.17 wt%) to commercial AZ91 alloy for enhancing the solid-solution strengthening effect and refining the crystal grains, respectively. The homogenized GR-AZ92 alloy with an average grain size of 91 μm exhibits a tensile yield strength (TYS) of 125 MPa, ultimate tensile strength (UTS) of 281 MPa, and elongation of 12.1%, which are significantly higher than those of AZ91 alloy with a grain size of 420 μm (TYS of 94 MPa, UTS of 192 MPa, and elongation of 7.0%). The peak-aging time of GR-AZ92 alloy (8 h) is significantly shorter than that of AZ91 alloy (32 h) owing to a larger amount of grain boundaries in the former, which serve as nucleation sites of Mg₁₇Al₁₂ precipitates. A short-aging treatment for less than 1 h of the GR-AZ92 alloy causes an effective improvement in its strength without a significant reduction in its ductility. The 30-min-aged GR-AZ92 alloy has an excellent combination of strength and ductility, with a TYS of 142 MPa, UTS of 304 MPa, and elongation of 8.0%.     

Microstructure and mechanical properties of as-extruded Mg-Sn-Zn-Ca alloy with different extrusion ratios

The effect of extrusion ratio on microstructure and mechanical properties of as-extruded Mg-6Sn-2Zn-1Ca (TZX621) (mass fraction, %) alloy was investigated. It is found that incomplete dynamic recrystallization (DRX) took place in as-extruded TZX621 alloy. As the extrusion ratio was increased from 6 to 16, both fraction of un-DRXed grains and average size of DRXed grains in as-extruded TZX621 alloy decreased and the basal texture was weakened. Coarse CaMgSn phase was broken into particles and fine Mg₂Sn phase precipitated from α-Mg matrix during hot extrusion. Yield strength, ultimate tensile strength and elongation of as-extruded TZX621 alloy with extrusion ratio of 16 reached 226.9 MPa, 295.6 MPa and 18.1%, which were improved by 36.0%, 17.7% and 13.5%, respectively, compared to those of as-extruded TZX621 alloy with extrusion ratio of 6.     

锶、钛对稀土改性压铸AZ91合金组织与性能的影响

研究了微量Sr、Ti对压铸AZ91合金微观组织与性能的影响。结果发现,与AZ91镁合金相比,添加稀土后,合金的强度提升、塑性下降。进一步添加Sr后,合金因组织细化而使塑性提升,但强度及耐腐蚀性降低。进一步添加Ti元素,则抑制了Sr元素的不利影响,并使合金保持良好的塑性。通过多元微合金化的方法使AZ91+RE+Sr+Ti合金达到最佳的综合性能。微观组织随组分添加而发生演变是材料性能变化的主要原因。     

Preparation of semi-solid billet of magnesium alloy and its thixoforming

Preparation of semi-solid billet of magnesium alloy and thixoforming was investigated by applying equal channel angularextrusion to magnesium alloy.The results show that mechanical properties of AZ91D alloy at room temperature,such as yieldstrength(YS),ultimate tensile strength(UTS)and elongation,are enhanced greatly by four-pass equal channel angularextrusion(ECAE)at 573 K and microstructure of AZ91D alloy is refined to the average grain size of 20μm.Through using ECAE asstrain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment,semi-solid billet with finespheroidal grains of 25μm can be prepared successfully.Compared with common SIMA,thixoformed satellite angle framecomponents using semi-solid billet prepared by new SIMA have higher mechanical properties at room temperature and hightemperature of 373 K.     

氩气处理对AZ91镁合金高温力学性能的影响

研究了氩气处理对AZ91镁合金高温力学性能的影响。结果表明,经过氩气处理后,每100g熔体中的氢含量从未处理的14.8cm^3降低至7.3cm^3,除气率高达50.7%;在20、100、175、250、325和400℃对合金分别进行拉伸试验,发现除气对合金抗拉强度和屈服强度的影响随温度升高而逐渐减小,但对伸长率的影响正好相反。在温度低于250℃时除气,合金强度显著提高,伸长率变化不明显,除气对在高温(250~325℃)拉伸时强度影响不大,但明显提高了镁合金的伸长率,另外,应变硬化指数(n)值相差不大(分别为0.04和0.03)。     

Preparation of AZ91D magnesium alloy semi-solid billet by new strain induced melt activated method

1 Introduction AZ91D magnesium alloy has received more attention due to its high specific strength, specific rigidity and good dimensional stability and so on[1]. Thixoforming is one of the best methods with regard to forming AZ91D magnesium alloy compone…