Effect of Cell Morphology and Heat Treatment on Compressive Properties of Aluminum Foams

In this article, the compressive behavior and anisotropy of both open- and closed-cell aluminum foams under different heat treatments were examined. For the closed-cell A356/SiCp foam, due to the age-hardening effect, the yield strength of the heat-treated specimens was found to be more than 200% of that of the as-cast specimens. The yield strength of the foam in the transverse direction was however only slightly higher than that in the longitudinal direction, which may be related to the relatively spherical cell structure of the foam. For open-cell Al6061 foams, heat treatment results in a significant increase in yield strength and also changes the failure mode from ductile to brittle. The open-cell foam further demonstrates a strong anisotropy. The causes of such phenomena are discussed in the article.     

Mechanics Modeling of the Compressive Stiffness and Strength of Open-Celled Aluminum Foams

This article presents the results of analytical modeling of the strength and stiffness of open-celled aluminum foams under compressive loading. The analytical models are based on a four-strut structure unit that was extracted from the real open-celled aluminum foam structure. Deformation and strength were first studied in the idealized structure unit bounds. The effects of asymmetric factors were also considered. The models predicted ranges in foam strength and stiffness as functions of relative densities, length ratio, and strut orientation. The predictions from the models were in good agreement with the experimentally measured strengths stiffnesses for open-celled aluminum foams.     

变形条件对2519A铝合金动态力学性能与组织演化的影响

为研究温度与应变率对2519A铝合金动态力学行为及组织演化的影响,采用霍普金森压杆对2519A铝合金进行了不同温度(-90~350℃)、不同应变率下的动态冲击压缩实验,分析了该合金的动态力学性能,并结合金相显微镜与透射电镜对合金在冲击变形后的微观组织进行分析。结果表明:在250~350℃的高温环境冲击下,合金的流变应力迅速下降,组织以形变带为主,同时组织内伴随有明显的动态回复和动态再结晶。在20~150℃的环境中进行动态冲击,合金变形时组织出现了典型的绝热剪切带特征。在室温、应变率达到8200s-1时,应变率强化效果发生转变。随着温度降至-90℃,在绝热剪切带内的组织出现了长度较短、连续性差的微裂纹,同时组织内的长条状第二相粒子发生不同程度的脆性断裂。     

开孔与闭孔泡沫铝的压缩力学行为

研究了开孔与闭孔两种胞孔结构不同、制备工艺不同的泡沫铝在准静态压缩载荷下的压缩响应曲线.结果表明:开孔与闭孔泡沫铝压缩应力-应变曲线均具有多孔泡沫材料明显的三阶段特征,即线弹性段、塑性屈服平台段及致密段;相对密度对泡沫材料的力学性能(如杨氏模量、屈服强度)有很大影响;在准静态下,开孔泡沫铝表现出明显的应变率效应,而闭孔泡沫不如开孔敏感;泡沫铝材料表现为弱的各向异性;胞孔结构影响两种泡沫材料的压缩响应曲线.     

2219铝合金动态力学性能及其本构关系

针对2219铝合金在高温、高应变率加工条件下的变形特征以及流动应力变化规律,利用分离式Hopkinson压杆设备对该合金进行了室温以及高温动态压缩力学性能研究,并利用电子万能试验机对其进行准静态压缩力学性能测试,得到了2219铝合金在不同应变率和温度下的真实应力-应变曲线。结果表明:2219铝合金对温度有较高的敏感性,其流动应力随着温度的升高而降低;当应变率在1000~3000s-1范围内时,材料的流动应力变化并不明显;基于Johnson-Cook模型拟合出的模型参数,能较好地预测实验中材料的流动应力。     

应变率对泡沫铝压缩性能的影响

泡沫铝作为抗冲击及减震材料,很多场合都要经受冲压变形.目前,关于泡沫铝在压缩过程中表现出的应变率效应说法不一.概述了应变率对泡沫铝压缩性能的影响,结果表明,由于泡孔的变形特性使泡沫铝具有明显的应变率效应,泡孔在变形过程中的局部化、微观惯性和致密化是其对应变率敏感的根本原因.在高应变率下,滞留气体对闭孔泡沫铝的压缩有一定影响,开孔泡沫铝对应变率的敏感度还未有统一结论.     

Ag合金化对热挤压前后耐热Al-Cu-Mg合金组织和性能的影响

采用拉伸力学性能测试和金相分析 ,研究了Ag合金化对热挤压前后耐热Al Cu Mg合金组织与性能的影响。结果表明 ,Ag的微合金化可以改善热挤压后Al Cu Mg合金的显微组织 ,明显提高合金的强度、延伸率及高温热稳定性。显微组织分析认为 ,这主要归功于合金化后析出的Ω相的沉淀硬化。     

焊接缺陷对铝合金焊接接头疲劳性能的影响

测定了Al Mg Si系6061合金两种焊接接头的疲劳性能,介绍了铝合金焊接接头的疲劳特征,分析了焊接接头中缺陷对铝合金焊接接头疲劳性能的影响,认为焊缝中宏观尺度的气孔和未焊透及其分布明显地影响铝合金焊接接头的疲劳性能,当缺陷尺寸足够大且数量较多时,将严重降低焊接接头的疲劳性能。夹杂对铝合金焊接接头疲劳性能也有严重的影响。     

Heat Transfer and Acoustic Properties of Open Cell Aluminum Foams

The aluminum open cell foams have been prepared by the conventional precision casting method to investigate the thermal and acoustic properties.A water heating system and silencers were organized as a first step for its applications.The temperature increase between the top and bottom of the foam became larger as the cell size increased in the heat transfer measurement.Sound absorption ratio of the close cell foams was 60%-100%, whereas the open cell aluminum foam showed only 10%-20% of sound absorption at low frequency.When the prototype electric water heater manufactured by combining aluminum open cell foam with a heater was heated to 100-400℃,the highest temperature of water was in the range of 16-46~C.This suggests that there could be potential for this type of heater to be used as a commercial electric water heater.Sound silencer made with the aluminum open cell foam was applied to exit of exhaustion side at air pressure line.Sound silencing effect of open-celled aluminum foam showed that the noise level went down by introducing smaller cell size foam.     

铝合金功能薄膜与溅射靶材

近年来 ,铝合金广泛用于生产多种功能薄膜。作为制备高性能溅射薄膜用的铝合金靶材也得到了相应的应用。本文重点介绍应用于不同领域的几种铝合金功能薄膜 ,简述了铝合金薄膜与溅射靶材的制备工艺、铝合金靶材的显微结构及其对溅射薄膜性能的影响 ,最后指出了铝合金薄膜及溅射靶材的发展趋势     

抗Zr“中毒”Al-Ti-B-C中间合金对7050铝合金力学性能的影响

通过场发射扫描电子显微镜(FESEM),X射线衍射仪(XRD),能量色谱仪(EDS)分析Al-5Ti-1B,Al-4Ti-1C和Al-5Ti-0.8B-0.2C中间合金的微观组织与物相组成,比较研究3种中间合金对7050铝合金晶粒尺寸与力学性能的影响。结果表明:Zr的存在削弱了Al-5Ti-1B和Al-4Ti-1C中间合金的细化效果,而对Al-5Ti-0.8B-0.2C中间合金细化效果影响较小。含掺杂型TiC粒子的Al-5Ti-0.8B-0.2C中间合金具有较好的抗Zr"中毒"能力,加入量为0.2%(质量分数,下同)时,含Zr7050铝合金平均晶粒尺寸由200μm细化至(60±5)μm,室温极限抗拉强度由405MPa提高到515MPa,提高了27.2%,伸长率由2.1%提高到4.1%。而加入0.2%的Al-5Ti-1B或Al-4Ti-1C中间合金时晶粒尺寸较粗大且分布不均匀,表现出明显的细化"中毒"。     

On the Mechanical Properties of Aluminum Matrix Syntactic Foams

Metal matrix syntactic foams (MMSFs, often referred as composite metal foams (CMFs)) are lightweight materials with high specific strength. MMSFs are on the borderline between metal matrix composites and metal foams. On one hand MMSFs are composites, because they are filled by hollow particles and the particles may add strength to the material. On the other hand, they are foams, because the hollow particles ensure porosity to the material. Among metallic foams, MMSFs exhibit outstanding specific mechanical properties due to the hollow inclusions that are typically made from ceramics or high strength alloys, therefore they can be applied as structural materials. The goal of this paper is to summarize the available data on the mechanical properties of MMSFs with aluminum matrix in order to give a strong support to the design engineers. Since the foams are most frequently loaded in compression, the main part of this paper is organized around the available standard related to the compressive properties of porous materials and metallic foams. The quasi‐static results are complemented by properties measured at higher strain rates. Besides this, some insight into the basic fatigue properties as well as into the toughness of MMSFs is also provided.

     

铝合金搅拌摩擦对接焊接头组织与性能研究

研究了5083铝合金搅拌摩擦焊(FSW)焊接接头组织与性能,采用金相显微镜观察焊接接头各区域的微观组织,并对接头显微硬度和力学性能进行了测定。结果表明,5083铝合金搅拌摩擦焊焊核组织为动态再结晶生成的细小组织,强化相均匀分布;热机影响区由于动态再结晶和焊接热循环的双重作用,组织变化较大,晶粒有一定程度的长大,强化相有所细化;热影响区仅仅受到热循环作用,使得晶粒粗化和强化相出现聚集现象。搅拌摩擦焊接接头中心硬度与母材基本相当,热机影响区和热影响区由于焊接热输入的原因,使得硬度有所降低。搅拌摩擦焊室温拉伸性能和冲击性能不低于母材的,其中拉伸试样均断裂于母材,焊核室温冲击值达到母材的1.5倍以上,热影响区冲击值与母材的相当。     

激光冲击处理对LY12CZ铝合金疲劳性能的影响EI

本文研究了激光冲击处理对铝合金疲劳寿命的影响，研究表明激光冲击处理可以大幅度地提高带有类似紧固孔铝板的疲劳寿命，初步讨论了提高寿命的原因。     

泡沫铝合金阳极氧化工艺研究

以草酸为电解液,对泡沫铝合金材料进行阳极氧化处理,制备多孔有序阳极氧化铝阵列模板,采用SEM扫描电镜对其形貌进行分析.研究了电流密度、电解液浓度、电解温度等条件对氧化铝膜结构的影响,并对一步法和两步法制得的多孔氧化铝膜进行了比较,结果表明,氧化膜上的微孔分布均匀,孔径大小基本相同;两步阳极氧化法制备的多孔氧化铝模板的有序性优于一步氧化法.     

稀土Er对A356铝合金微观组织和力学性能的影响

针对传统的A356铝合金,添加稀土元素是改善其微观组织并提高力学性能的有效途径。本工作通过示差扫描量热分析(DSC)、X射线衍射(XRD)、扫描电镜(SEM)等分析手段来研究稀土Er对铸态A356铝合金组织和性能的影响。结果表明,稀土元素Er是一种能够显著改善A356合金铸态组织的优良变质剂。Er的加入细化了初生α-Al相,二次枝晶间距降低,枝晶臂直径减小,同时对铸态组织中的共晶Si起到了变质作用。当Er含量达到0.4%(质量分数,下同)时,细化效果最为显著,二次枝晶间距由53.6μm减小到17.5μm,共晶硅形貌也由粗大的板条状转变为短棒或圆粒状。与A356合金相比,添加0.4%Er的合金样品的抗拉强度和伸长率分别提高了15.1%,29.8%。     

稀土钇对2519合金组织及耐热性能的影响

采用X射线、光学显微镜、扫描电镜及透射电镜等手段研究了微量稀土Y对2519合金的显微组织及耐热性能的影响.结果表明,在2519合金中Y元素与Cu,Al元素主要形成Al6Cu6Y金属间化合物,并沿晶界分布.这些金属间化合物有效阻碍高温时基体的变形和晶界的移动,提高合金高温强度.添加0.20%Y(质量分数)可使合金200℃时的抗拉强度提高30%,但伸长率有所下降.Y含量的进一步增加,含Y化合物聚集长大成块,合金室温及高温力学性能降低.同时发现,微量的Y细化了合金的再结晶组织,细化了合金强化相θ′相.添加0.10%Y时可使合金的室温强度提高20MPa.     

金字塔形栅格材料与胞状铝合金的准静态压缩性能

在金字塔形栅格材料、胞状铝合金压缩试验的基础上研究其力学性能、吸能能力和吸能效率,结果表明,金字塔形栅格材料的单轴压缩应力-应变曲线呈现线弹性变形、弹塑性、软化、致密化等4个阶段,与胞状铝合金的压缩性能相比,其压缩强度更高,吸能能力更好。     

稀土对ZA27合金压蠕变的影响

采用自制的实验装置研究了稀土 (Ce≥ 45 % )对ZA2 7合金在常温及高温时的压蠕变行为的影响。研究表明 ,在所试验的温度为 2 0℃～ 160℃和压应力为 5 0MPa～ 13 7 5MPa的范围内 ,加稀土的ZA2 7—RE合金和未加稀土的ZA2 7合金的压蠕变量均随着温度和应力的升高而增大 ,ZA2 7—RE合金的压蠕变速率小于ZA2 7合金的压蠕变速率。加入稀土后 ,合金在压蠕变过程中的负蠕变量及出现负蠕变的温度和应力范围增大。两种合金的稳态蠕变速率均符合于半经验公式ε　 's=Aσnexp( -Qa RT)。但在不同的温度 ,ZA2 7—RE合金的应力指数平均值n( 4 66)和表观激活能平均值Qa( 70 45KJmol- 1 )均大于ZA2 7合金的应力指数平均值n( 3 87)和表观激活能平均值Qa( 68 2 2KJmol- 1 ) ,而合金的材料结构常数A为 4 82× 10 - 5,低于ZA2 7合金的材料结构常数A( 0 0 0 2 )。两种合金的稳态蠕变速率均是由锌的点阵自扩散和位错的攀移所控制