共查询到20条相似文献,搜索用时 15 毫秒
1.
《Materials Science & Technology》2013,29(5):574-578
AbstractWeight reduction to improve automobile fuel economy has triggered renewed interest in magnesium. The effects of Ca/Sr separate and composite additions to AZ91D magnesium alloy on its microstructure and mechanical properties have been investigated. The results indicate Ca can refine both the grain and eutectic phase of AZ91D magnesium alloy. Sr hampers microstructure refinement when composite Ca/Sr additions are made. In addition, separate Ca additions to AZ91D magnesium alloy increase yield strength but decrease elongation of this alloy. By adjusting the Ca/Sr composite proportions, additions to AZ91D magnesium alloy are able to improve both microstructure and mechanical properties of the alloy. 相似文献
2.
Yongbing Li Yunbo Chen Hua Cui Baiqing Xiong Jishan Zhang 《Materials Characterization》2009,60(3):240-245
The AZ91 magnesium alloy, preformed with complete shape, has been prepared using spray forming technology under a protective atmosphere. The microstructure and mechanical properties have been investigated. Initially, a homogeneous and equiaxed-grain structure with average grain size of 20 μm was obtained. The tendency for segregation of the divorced eutectic β(Mg17Al12) phase towards the grain boundary was greatly reduced. Further grain refinement was attributed to dynamic recrystallization during extrusion processing. When solution treated at 415 °C and aged at 175 °C, two kinds of β(Mg17Al12) precipitates are formed: the majority are lamellar discontinuous precipitates, in addition to a small amount of dispersed continuous precipitates. The average tensile ultimate and yield strength of the spray-formed and extruded AZ91 magnesium alloy samples were 435 MPa and 360 MPa with a room temperature elongation of 9.2%, indicating an enhanced combination of toughness and strength. 相似文献
3.
A new semisolid metal processing technology, rheo-diecasting (RDC) has been developed for production of Mg-alloy components
with high integrity. The RDC process innovatively combines the dispersive mixing power of the twin-screw mechanism for creation
of high quality semisolid slurry and the high efficiency, low cost nature of the high pressure die casting (HPDC) process
for component shaping. AZ91D Mg-alloy was used to optimise the RDC process and to establish its advantages over both the HPDC
process and other existing semisolid processing techniques. In this paper we present the RDC process for processing Mg-alloys
and the resulting microstructure and mechanical properties of RDC AZ91D alloy. The solidification behaviour of the Mg-alloys
in the RDC process and the co-relationships between microstructure and mechanical properties of the RDC AZ91D alloy are discussed.
It was found that the RDC process is capable of producing Mg-alloy samples with close-to-zero porosity and a fine, uniform
microstructure throughout the entire sample irrespective of the section thickness. Compared with those obtained by other existing
processing techniques, the RDC samples have substantially improved or equivalent mechanical properties, with the tensile elongation
showing more than 100% improvement. 相似文献
4.
Microstructure evolution of the extruded AZ80 magnesium alloy and different precipitation behavior of β-Mg17Al12 phase in different heat treatment conditions were investigated. Solution treatment caused the dissolution of β-Mg17Al12 phase and the grain coarsening. During aging, discontinuous precipitates were preferentially initiated at some of the grain boundaries and then continuous precipitates appeared in the grain interiors. In the period of direct-aging, discontinuous precipitates formed between the banded structure and no continuous precipitate appeared. After solution and aging treatment, an improved combination of strength and elongation was obtained. The highest strength was achieved for the extruded AZ80 sample after directing-aging treatment. 相似文献
5.
采用控制变量法研究单一稀土Y和复合稀土Y,Sm元素对AZ91D镁合金微观组织与力学性能的影响,分析稀土元素对AZ91D合金的细化机理。结果表明:复合添加稀土Y和Sm对AZ91D合金的作用效果明显好于单一添加稀土Y对AZ91D合金的作用效果,添加Y和Sm后,生成了块状相Al2Y相和针状相Al2Sm相,可以作为α-Mg的有效异质形核点。当加入量为0.8%(质量分数,下同)Y+1.0% Sm时,α-Mg晶粒尺寸最为细小,分布最为均匀,其合金的硬度、抗拉强度及伸长率分别为67.42HV,153.37 MPa和3.62%,改善了铸态AZ91D合金的室温力学性能,但是超过这个最佳添加量后,合金的室温力学性能开始下降。 相似文献
6.
Journal of Materials Science - AZ91 casting alloy is subjected to friction stir processing (FSP) in air (NFSP) and under water (SFSP). The thermal histories of the two FSP procedures are measured,... 相似文献
7.
固溶处理对AM60B+XRE及AZ91D+XRE 镁合金性能的影响 总被引:6,自引:0,他引:6
研究了添加少量富铈混合稀土的AM60B+xRE及AZ91D+xRE合金(x=0.4、0.8、1.2、1.6和2.0%,质量分数)固溶处理后的显微组织与机械性能.结果表明,添加混合稀土能显著提高合金的抗拉强度σb和屈服强度σ0.2,固溶处理明显提高AZ91D+xRE合金的强度;AM60B+xRE及AZ91D+xRE合金的铸态组织由α(Mg)固溶体、杆状Al11RE3相、颗粒状Al10Ce2Mn7相以及网状Mg17Al12相组成,经过固溶处理后,网状Mg17Al12相完全溶解,只剩下热稳定性较高的Al11RE3相和Al10Ce2Mn7相,随固溶时间的延长,其形态略有改变.AM60B+xRE合金拉伸试样断口呈带局部韧窝的准解理断裂形式,而AZ91D+xRE合金则呈现沿晶断裂+解理断裂的混合断口形态. 相似文献
8.
固溶处理对AM60B+xRE及AZ9lD+xRE镁合金性能的影响 总被引:24,自引:0,他引:24
研究了添加少量富铈混合稀土的AM60B xRE及AZ9lD xRE合金(x=0.4、0.8、1.2、1.6和2.0%,质量分数)固溶处理后的显微组织与机械性能.结果表明,添加混合稀土能显著提高合金的抗拉强度σb和屈服强度σ0.2,固溶处理明显提高AZ9lD xRE合金的强度;AM60B xRE及AZ9lD xRE合金的铸态组织由α(Mg)固溶体、杆状Al11RE3相、颗粒状Al10Ce2Mn7相以及网状Mg17Al12相组成,经过固溶处理后,网状Mg17Al12相完全溶解,只剩下热稳定性较高的Al11RE3相和Al10Ce2Mn7相,随固溶时间的延长,其形态略有改变.AM60B xRE合金拉伸试样断口呈带局部韧窝的准解理断裂形式,而AZ9lD xRE合金则呈现沿晶断裂 解理断裂的混合断口形态. 相似文献
9.
利用平行板触变压缩仪研究了电磁搅拌的半固态AZ91D合金试样的压缩变形和组织.结果表明:随着半固态压缩变形温度的升高,AZ91D镁合金试样变形的速度加快,即变形应变速度增大,但压缩应力不断下降;在某一载荷下,AZ91D镁合金试样压缩变形应力和应变呈明显的线性关系,与压缩温度的高低无关.随着半固态压缩载荷的提高,AZ91D镁合金试样变形的速度增加,应变速度增大,应力下降速度加快;在不同的压缩载荷下,AZ91D镁合金试样的压缩变形应力和应变都呈明显的线性关系.在实验中的各种半固态压缩变形条件下,初生α-Mg在压缩后AZ91D镁合金试样组织中的分布很均匀,几乎不存在组织偏析.当初生固相的形态呈球状结构,在相同的变形条件下,不同种类合金的半固态压缩变形规律非常相似. 相似文献
10.
《材料科学技术学报》2017,(9)
The current research investigates the effect of homogenization on the microstructure and mechanical properties of the AZ91 D alloy processed by repetitive upsetting(RU). Results show that during RU processing, the initial large Mg_(17)Al_(12) particles in the as-cast specimen accelerate the dynamic recrystallization(DRX) due to the particle stimulating nucleation(PSN) mechanism. With the progress of RU,the inherent large strain breaks the large second phases into small fragments, which indicates the PSN gradually disappears, while the pinning effect becomes obvious. As for the homogenized specimen, a pre-heat treatment leads to the absence of Mg_(17)Al_(12) particles but a uniform distribution of Al atoms in the Mg alloy. Though the subsequent RU promotes the precipitation of Mg_(17)Al_(12) particles, the relatively small particle size and the uniform distribution are more favorable to act as obstacles for grain growth than contributors to PSN. Finally, a more homogeneous and refined microstructure is obtained in the specimen with prior homogenization than the as-cast one. 相似文献
11.
《Materials Science & Technology》2013,29(6):698-701
AbstractA two step isothermal heating process was developed to prepare a semisolid slurry of AZ91 alloy. In the process the alloy was heated isothermally at its liquidus temperature, cooled to a semisolid temperature, and then heated isothermally at the temperature before it was deformed. This relatively simple method was found to be a highly efficient way to generate a non-dendritic microstructure. The influence of strontium addition on the soundness of semisolid formed parts was also studied. AZ91 alloy is prone to shrinkage porosity because the freezing range of the alloy is wide. Porosity formation during the process was observed to be suppressed by the microaddition of strontium. 相似文献
12.
Effect of neodymium on microstructure and corrosion resistance of AZ91 magnesium alloy 总被引:2,自引:0,他引:2
Y. L. Song Yao Hui Liu S. R. Yu X. Y. Zhu S. H. Wang 《Journal of Materials Science》2007,42(12):4435-4440
The corrosion behavior of a new Mg–9Al–1Zn (AZ91) magnesium alloy containing neodymium (Nd) is investigated by scanning electron
microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), immersion tests and electrochemical experiments.
The results indicate that Nd decreases the size and volume fraction of the β (Mg17Al12) phase and forms Al2Nd in the alloy. In addition, during corrosion, Nd is incorporated into corrosion film in the form of Nd2O3. AZ91 alloy containing 1.0 wt.% Nd possesses an outstanding passivation property and excellent corrosion resistance. The
corrosion resistance enhancement is attributed to the reduction in the size and volume fraction of the β phase and the incorporation
of Nd2O3 in the corrosion film. 相似文献
13.
Ling Wang Young Min Kim Jehyun LeeBong Sun You 《Materials Science and Engineering: A》2011,528(3):943-949
The present study aims to investigate the effect of carbon addition on the hot rolling behavior of as-cast AZ91 alloy. The AZ91 and C-added AZ91 alloys were subjected to hot rolling at 400 °C with a reduction of 30% per one pass. The as-cast C-added AZ91 alloy with very fine equi-axed grains of approximately 75 μm exhibited excellent hot rollability compared to as-cast AZ91 alloy with coarse dendrite structure, although the final grain size of the rolled C-added AZ91 alloy sheet was slightly larger than that of the rolled AZ91 alloy sheet. The side-crack occurrence on the surface during hot-rolling is mainly affected by the existence of twin boundary and the area fraction of grain boundaries. Based on the results, the improvement in rollability of the C-added AZ91 alloy is attributed to fine equi-axed grains and the polygonal Al8Mn5 phase located inside grains, which can homogeneously distribute and effectively absorb strain energy and prohibit crack growth. 相似文献
14.
《Materials Science & Technology》2013,29(11):1674-1679
AbstractThe influences of rare earth neodymium on microstructure and mechanical properties of as cast and hot rolled AZ31B wrought magnesium alloy were investigated. The results show that the mechanical properties of both as cast and hot rolled AZ31B alloys decrease due to Nd addition. Nd reacts with Al to form Al2Nd phase when Nd is added. Bulky and brittle Al2Nd intermetallic degrades the mechanical properties. Moreover, the addition of Nd weakens the grain refining effect of Al on as cast AZ31B alloy, resulting in grain coarsening. Coarse grains also cause the decline of the mechanical properties of as cast AZ31B–Nd alloy. The negative influence of the bulky and brittle intermetallics on mechanical properties of AZ31B alloy can be relieved by large deformation because the intermetallics can be sufficiently broken up during the deformation process. 相似文献
15.
16.
采用Si-RE元素对AZ31镁合金进行复合微合金化,利用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)及拉伸实验仪等手段研究Si-RE元素对AZ31镁合金的微观组织和力学性能的影响规律。结果表明,Si-RE复合加入可以明显细化AZ31镁合金的铸态组织,β-Mg17Al12相也由网状分布变为颗粒状,同时生成了短棒状和针状的Mg2Si相及Al11RE3相;合金的综合力学性能显著改善,AZ31+0.4%Si+0.5%RE的强度和延伸率比原始AZ31镁合金分别提高了42MPa和3.9%,试样室温拉伸断口虽然是以解理为主的脆性断裂,但断口中出现了少量的韧窝,解理面也较小。 相似文献
17.
Microstructures and mechanical properties of AZ91 alloy with combined additions of Ca and Si 总被引:1,自引:0,他引:1
Ca and Si additions to AZ91 alloy have been investigated and the results show that addition of Ca or Ca combined with Si resulted in the refinement of the as-cast microstructure, increase the thermal stability of β phase and the inhibition of discontinuous precipitations. Small amounts of Ca added to the AZ91 alloy mainly dissolved into β phase and raised the thermal stability of the phase, thus strengthening the alloy at elevated temperatures. Combined additions of Si with Ca to the AZ91 alloy were more effective on increasing the tensile strength at both ambient and elevated temperatures. The creep resistance of the alloy was also improved significantly in the alloy with Ca and Si additions. The creep rate of the alloy containing 0.3% Ca and 0.6% Si, tested at 473 °K and 50 MPa, was one order of magnitude lower than that of the base alloy (without Ca and Si addition). The mechanism of mechanical properties improvement caused by Ca and Si was also discussed. 相似文献
18.
消失模铸造AZ91镁合金的研究 总被引:12,自引:1,他引:12
研究了ZA91镁合金消失模铸造时铸件的厚度,位置和真空度对铸件质量,组织及力学性能的影响,真空度是决定铸件质量的一个关键的工艺因素,无真空时浇注铸件易产生浇不足缺陷,但真空度过大又会导致形成粘砂和气孔等缺陷,真空浇注射明显细化组织,但真空度进一步增大时细化效果野 不明显,铸件显微组织具有很大的壁厚效应,然 位置对组织的影响与是否采用抽真空措施有关,铸件壁厚较小时,铸件的力学性能总体较差,断裂源自Mg/Mg17Al12界面、且主要是以解决理形式的脆性断裂。 相似文献
19.
ABSTRACTIn-situ magnesium matrix nano-composites were produced through a reaction of CO2 with the AZ91 alloy at a semi-solid temperature range. The process was performed at 595°C, which corresponded to about 10% of solid fraction, under shear and mixing conditions generated by a screw-barrel system. As a result, nano-scale native MgO (30–50?nm) and a small amount of Al4C3 carbide within an eutectic consisting of α(Mg), β-Mg17Al12 were formed. Homogeneously distributed α(Mg) globular grains with volume 8–12% were visible. AZ91 composites revealed yield strength of 220?MPa at compression strength of 460?MPa and hardness 103?±?2?HV. 相似文献
20.
《Materials Science & Technology》2013,29(7):1138-1142
AbstractThe effects of neodymium rich rare earth elements [RE(Nd)] on microstructure and mechanical properties of as cast AZ31 magnesium alloy were investigated. The microstructures of as cast AZ31–xRE(Nd) alloys display a dendrite configuration, and the secondary dendrite spacing of the α-Mg phase was decreased with the increasing Nd content. The addition of RE(Nd) resulted in the formation of Al2Nd and Mg12Nd phases. Mechanical properties were improved significantly due to grain refinement and precipitation of intermetallic phases. When the amount of RE is 1·0 wt-%,The as cast AZ31 alloy reached its maximum tensile strength of 249 MPa at room temperature, yield strength of 169 MPa and elongation of 9·0%. 相似文献