共查询到20条相似文献,搜索用时 639 毫秒
1.
2.
SiCw/LD2A1复合材料超塑变形协调机制的研究 总被引:2,自引:2,他引:0
为了研究金属基复合材料超塑变形时液相的作用,分析了金属基复合材料界面处的局部应力,当由滑移引起的界面处局部分应力值高于界施加于同处应力值时,复合材料在含有液相的状态下超塑变形能力量大,反之,变形能力在不含液相的纯固相状态最大,因此,可以认为塑性变形过程中当有应力集中产生时,为了缓解应力集中,液相必需存在才能取得超塑性,当无应力集中时,超塑变形不需要液相的存在,上述理论与实验结果是一致的。 相似文献
3.
4.
5.
通过建立轴对称体胞模型,用数值分析手段研究了在变形速率范围10-4~105/s内,陶瓷颗粒增强铝合金复合材料的压缩塑性流变特征,讨论了不同颗粒形状(圆柱形和球形),不同颗粒体积含量(10%~50%)和不同铝合金基体(LC4、LY12CZ和7075)对金属基复合材料流动应力、应变率敏感性等的影响,构造了可以描述高应变率下金属基复合材料压缩行为的本构模型,并考虑了基体特性、颗粒形状、体积含量及应变率的影响,得出了与试验相吻合的结果。 相似文献
6.
7.
8.
9.
本文对Zn-22%Al材料超塑性状态与非超塑状态进行了挤压及镦粗变形对比,实测了硬度分布及网格变化,对变形区组织也进行了分析。结果表明,由于超塑性状态的应变速率强化敏感及边界粘性摩擦的影响使其变形的特点与非超塑性状态有着明显的区别。对于超塑性状态的正挤压与反挤压变形可观察到其变形区较深,网格畸变剧烈,但是显微组织在各部位变化不大。由于超塑性细晶粒弥散强化的影响,无论是挤压变形还是镦粗变形,超塑性状态的硬度比非超塑性状态的略高。对于镦粗变形,超塑性状态的鼓形肚曲率半径较非超塑性的大。 相似文献
10.
11.
The optimum materials design in microstructural control could be developed for the high-strain-rate superplastic materials
in the industrial scale. In the present work, it is reported that the high-performance-engine pistons with near-net-shape
can be fabricated by the superplastic forging technology in the high-strain-rate superplastic PM Al-Si based alloy, which
is produced by using this optimum materials design.
Received: 8 February 2000 / Reviewed and accepted: 13 September 2000 相似文献
12.
Superplastic tensile tests of a 17 vol.% SiC
p
/8090 Al-Li composite were carried out at strain rates ranging from 7.25 × 10-4 s-1 to 3.46 × 10-1 s-1 and at temperatures from 773 K to 873 K. A maximum elongation of 300% was obtained at a strain rate of 1.83 × 10-1 s-1 when tested at a temperature of 848 K which was slightly above the solidus temperature of the composite. The effect of a small fraction of liquid phase on high-strain-rate superplasticity was discussed. Finally, the activation energy of high-strain-rate superplastic deformation was calculated and high-strain-rate superplastic mechanism was discussed. 相似文献
13.
Reactive spray atomization and deposition processing is currently being studied as an approach for the in‐situ synthesis of Al metal matrix composites (MMCs). In the present paper, the latest developments in this field are reviewed, with an emphasis on in‐situ reaction kinetics, grain size refinement and mechanisms, and superplastic forming behavior; and future work is also discussed. 相似文献
14.
Superplasticity of fine-grained magnesium alloys for biomedical applications: A comprehensive review
《Current Opinion in Solid State & Materials Science》2023,27(2):101058
The superplastic behavior of medical magnesium alloys is reviewed in this overview article. Firstly, the basics of superplasticity and superplastic forming via grain boundary sliding (GBS) as the main deformation mechanism are discussed. Subsequently, the biomedical Mg alloys and their properties are tabulated. Afterwards, the superplasticity of biocompatible Mg-Al, Mg-Zn, Mg-Li, and Mg-RE (rare earth) alloys is critically discussed, where the influence of grain size, hot deformation temperature, and strain rate on the tensile ductility (elongation to failure) is assessed. Moreover, the thermomechanical processing routes (e.g. by dynamic recrystallization (DRX)) and severe plastic deformation (SPD) methods for grain refinement and superplasticity in each alloying system are introduced. The importance of thermal stability (thermostability) of the microstructure against the grain coarsening (grain growth) is emphasized, where the addition of alloying elements for the formation of thermally stable pinning particles and segregation of solutes at grain boundaries are found to be major controlling factors. It is revealed that superplasticity at very high temperatures can be achieved in the presence of stable rare-earth intermetallics. On the other hand, the high-strain-rate superplasticity and low-temperature superplasticity in Mg alloys with great potential for industrial applications are summarized. In this regard, it is shown that the ultrafine-grained (UFG) duplex Mg-Li alloys might show remarkable superplasticity at low temperatures. Finally, the future prospects and distinct research suggestions are summarized. Accordingly, this paper presents the opportunities that superplastic Mg alloys can offer for the biomedical industries. 相似文献
15.
《Materials Science & Technology》2013,29(7-8):759-764
AbstractFrom a commercial viewpoint superplastic forming of complex shapes using only a single operation and one surface tool is appealing, especially for metal matrix composites (MMCs) that are hard to form even at elevated temperatures due to low ductility and toughness. Furthermore, secondary machining operations are difficult due to the presence of extremely hard ceramic reinforcements such as SiC. A range of aluminium alloy based MMCs have indeed been shown to exhibit superplastic properties although most of these studies have been concerned with microstructural characterisation using small uniaxial tensile specimens. This paper therefore concentrates on high strain rate biaxial superplastic forming of complex shapes (critical feature) in MMCs where a forming envelope has been defined and post-forming mechanical properties investigated. Particulate reinforced MMCs based on aluminium alloys 7475 and 7178 were superplastically formed in a die with a 45° step at a range of temperatures and pressures. Formed specimens were sectioned to investigate cavitation and cross-sectional thinning. Tensile tests were performed on parent and formed material to investigate the effect of superplastic forming on mechanical properties. The MMCs were successfully formed over the temperature range 450–550°C achieving step angles α of 22–42°. This study has shown that high strain rate superplasticity (~10-1 s-1)can be achieved giving a strain of 70% in only 3.5 s without SiC fracture, reinforcement–matrix decohesion or matrix cavitation making this technique economic and very attractive for commercial exploitation. Cross-sectional thinning was found to be uniform and in the order of ~25% which could be accounted for at the design stage. The high strain rate superplasticity was found to be grain size dependent (<3 µm) but greater profile definitions were achieved when forming took place just above the matrix solidus. Superplastic forming above the matrix solidus temperature resulted in the achievement of the highest step angles in the complex shapes but had a detrimental effect on mechanical properties. This is thought to be due to the liquid phase present that aids grain boundary and interfacial sliding but has a similar effect to overheating during solution treatment and brittle phases are formed at the grain boundaries. 相似文献
16.
17.
Metal Matrix Composites (MMCs) are potential candidate materials in the aerospace and automobile industries because of its attractive properties, in particular, their high specific properties, and Superplastic forming (SPF) is a good solution to the problems in the forming process of MMCs due to their low ductility resulting from the incorporation of reinforcement. High strain rate superplasticity (HSRS) is attractive for industrial applications because superplastic forming at high strain rates can reduce forming time greatly. The strength of P/M 6061 Al and 6061 Al/SiCp (3 m) composites during superplastic deformation at temperatures of 853 K–871 K and a high strain rate of 0.1 s–1 has been studied in this paper. Experimental results presented a softening effect by the SiCp reinforcement. Mechanical and microstructural analyses show that the decrease in the strength during high strain rate superlastic (HSRS) deformation is associated with the decreased grain size of the Al matrix with increase of the SiCp volume fraction or the extrusion ratio, and the occurrence of liquid phase. The formation of the liquid phase was related to segregation of the solute atom during HSRS deformation. 相似文献
18.
T. Hirata T. Mukai N. Saito S. Tanabe M. Kohzu K. Higashi 《Journal of Materials Science》2003,38(19):3925-3932
The deformation mechanism in high-strain-rate superplastic P/M7475 before and after continuous dynamic recrystallization (CDRX) was investigated. The recrystallization process in P/M7475 differed from that in conventional superplastic material, I/M7475. In I/M7475, the fine-grained microstructure was obtained by static recrystallization before deformation. On the other hand, the substructure in P/M7475 evolved into fine grains during deformation by CDRX. The percentage of high-angle and random boundaries was low at an initial stage of deformation. However, it increased with strain in P/M7475. The microstructural change in P/M7475 influenced a deformation mechanism and affected grain boundary sliding (GBS). The ratio of contribution of GBS to total elongation was low at an early stage of deformation in P/M7475. However, it increased with deformation progressed. It is suggested that the deformation behavior in P/M7475 changed from dislocation creep to superplasticity as the dominant deformation mechanism changed to GBS. The activation energy for superplastic flow in P/M7475 was close to that for lattice self-diffusion in pure aluminum. It is therefore concluded that the dominant deformation mechanism after CDRX in P/M7475 is GBS accommodated by dislocation movement controlled by lattice self-diffusion, similar to that in I/M7475. 相似文献
19.
原位自生钛基复合材料研究综述 总被引:1,自引:0,他引:1
近年来,由于原位自生钛基复合材料相对钛合金更为优异的综合性能,引起人们广泛关注。从制备方法、基体和增强体选择、微观结构、力学性能、抗氧化性能、超塑性变形与加工等方面,综述了目前原位自生钛基复合材料的研究进展。提出了目前研究中存在的问题和今后可能的发展方向。 相似文献
20.
Formability of a high-strain-rate superplastic Al–4.4Cu–1.5Mg/21SiCW composite under biaxial tension
The cavitation behavior and forming limits of a high-strain-rate superplastic 21 vol.% SiC whisker-reinforced Al–4.4Cu–1.5Mg (Al–4.4Cu–1.5Mg/21SiCW) under biaxial stress states were investigated in this paper. The composite sheet was bulged using dies with aspect ratios of 1:1, 4:3 and 2:1 at the constant applied stress of 4 MPa and at the optimal temperature of 793 K determined from superplastic tensile tests. The thickness distributions of bulged diaphragms were measured at different strain levels. For diaphragms deformed equibiaxially, a good agreement between experimental thickness distributions and the theoretical predictions of Cornfield and Johnson (Int. J. Mech. Sci. 12 (1970) 479) was observed at fractional heights of the deformed diaphragms ranging from 0.4 to 1.0. The cavitation behavior of the composite under biaxial tension was compared with that of uniaxial tension. It was found that at a similar effective strain, the amount of cavities obtained under equibiaxial tension is slightly greater than that under uniaxial tension, and the cavity growth rate parameter under uniaxial tension was also slightly larger than that of uniaxial tension. The influence of stress state on cavity growth rate was discussed. Limit strains of Al–4.4Cu–1.5Mg/21SiCW at different stress ratios were predicted based on a plastic damage model recently developed for superplastic materials (Chan and Chow, Int. J. Mech. Sci., submitted). The trend of the prediction was in good agreement with the experimental findings. 相似文献