新型高强度胞状铝合金的压缩及能量吸收性能

测量了新型轻质（0.14-0.09ρ0，ρ0为纯铝的密度）高强度胞状铝合金（ZL111）的压缩应力（σ）－应变（ε）曲线，研究了材料的能量吸收性能与密度的关系，胞状铝合金的压缩σ-ε曲线与胞状纯铝相似分为三个部分：弹性阶段、平台阶段和压实阶段。胞状铝合金的压缩屈服强度σa比后者高40％以上，其σ-ε曲线呈锯齿状，平台斜度（dσdε)比后者小，因而具有更高的能量吸收能力（C）和能量吸收效率（e），当ε为0.15-0.6时吸能效率达到峰值0.85。     

高比强泡沫铝合金中空层合圆管的性能

设计制备了高比强泡沫铝合金中空层合圆管，测出了圆管的压缩应力-应变(σ-ε)曲线并研究了其性能．圆管与泡沫铝合金的压缩σ-ε曲线相似，但有较小波动；圆管的弹性模量与面板的弹性模量成线性关系，线性系数为η α（0.5η^2 0.3η）（1-η)；泡沫铝合金中空层合圆管的紧实应变(εD)可用泡沫铝合金的εD表示．由σ-ε曲线计算出圆管的能量吸收性能，发现其吸能能力(VV)大约比铝合金面板和泡沫铝合金的吸收能量之和高60％，吸能效率(且)高于60％．泡沫铝合金中空层合圆管具有轻质(ρ＜1）特性，但是其压缩比强度σ/ρ和压缩比刚度量E／ρ是泡沫铝合金相应参数的3倍．     

轴对称平面应力状态屈服轨迹上的应变变化规律

本文将诸薄筒件成形工序,按照主应力的大小顺序、找出其在轴对称平面应力状态屈服轨迹上所对应的区域,进而给出无摩擦条件ε_θ、ε_ρ和ε_τ随角φ=tg~(-1)σ_ρ/σ_θ的变化规律。文章还给出了锥面成形工序在有摩擦条件下,ε_θ、ε_ρ和ε_τ沿φ角的分布曲线。     

球形孔泡沫铝合金三明治梁的三点弯曲变形

研究了球形孔泡沫铝合金的单轴压缩性能,得到了抗压强度与相对密度的关系;与多边形孔泡沫铝合金和泡沫纯铝作了对比,发现球形孔使力学性能有了较大的提高.根据球形孔泡沫铝合金三明治梁三点弯曲的载荷(P)位移(δ)曲线研究了四种常见破坏模式并建立了破坏模式图.用极限载荷公式得到的计算值与极限载荷的实验值吻合良好.球形孔泡沫铝合金力学性能高于多边形孔泡沫铝合金及泡沫纯铝,因而其三明治梁的力学性能最好.     

泡沫铝填充薄壁铝合金多胞构件与单胞构件吸能性能研究

为研究泡沫铝填充薄壁铝合金多胞结构与单胞结构的吸能能力,该文基于有限元软件LS-DYNA建立了泡沫铝填充薄壁铝合金多胞结构与单胞结构的数值仿真。对经典薄壁圆管试验及泡沫铝填充薄壁圆管试验进行了数值模拟,分析表明该数值模型能够较好的模拟泡沫铝填充薄壁圆管在轴向冲击过程中的撞击力和变形发展。基于该模型对比研究了不同因素下泡沫铝填充薄壁铝合金多胞结构与单胞结构的轴向吸能特性,分析了其破坏模式、吸能机理和两者吸能效率。结果表明:在轴向冲击荷载作用下,泡沫铝填充薄壁铝合金的破坏模式为轴对称渐进折叠破坏模式,冲击力-位移曲线和变形模态图显示其变形过程分为3个阶段:弹性阶段、平台阶段和强化阶段。当冲击压缩距离为构件高度的80%时,7种不同参数下的泡沫铝填充薄壁铝合金多胞结构的吸能效率明显高于7种单胞结构,吸收的能量E和比吸能SEA都提高了50%以上,是一种优秀的吸能构件,可广泛应用于防护工程中。     

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。     

纸浆模塑制品缓冲性能及其缓冲包装设计方法研究

提出了等效面积理论,通过静态压缩试验获得了纸浆模塑制品的应力(σ)-应变(ε)曲线、缓冲系数(C)-最大应力(σ_m)曲线,基于等效面积理论对纸浆模塑制品缓冲包装设计方法进行了实例分析。     

工业闭孔泡沫铝压缩力学性能及变形机理

泡沫铝是一种新型的结构和功能材料,因特殊的能量吸收特性而在工程领域具有很好的应用前景。为了研究基体材料对泡沫铝力学性能和变形失效机理的影响,同时为工业泡沫铝材料提供更具参考价值的性能指标,对工业上最常见的两种不同基体(纯铝基体和7050铝合金基体)的泡沫铝材料进行了准静态压缩力学性能的试验,并对其变形机理进行了分析。试验结果表明,相同规格的7050基体泡沫铝的压缩力学性能高于纯铝基体泡沫铝,能量吸收能力也远大于纯铝基体泡沫铝。纯铝基体泡沫铝在压缩载荷下呈现逐层坍塌、连续性破坏的模式,试件在完全压实后呈碎渣;7050基体泡沫铝表现出逐层坍塌、间断式破坏的模式,试件在完全压实后呈完整的块状。7050基体泡沫铝的泡孔结构比纯铝基体泡沫铝均匀,力学性能更加稳定。     

泡沫铝填充薄壁铝合金多胞板与单胞板吸能性能研究

为研究泡沫铝填充薄壁铝合金多胞板(MCP)与单胞板(SCP)的吸能能力,该文设计了6种不同截面的泡沫铝填充薄壁铝合金多胞板与1种单胞板,并基于非线性有限元软件LS-DYNA建立了相应的数值模型。对经典铝合金板耐撞击试验及泡沫铝夹芯板耐撞击试验进行了数值模拟,分析表明该数值模型能较好的模拟泡沫铝夹芯板在冲击过程中的撞击力、挠度和变形形态。基于此模型对比研究了不同因素下多胞板与单胞板的吸能特性,分析了其破坏模式和吸能机理,最后通过正交试验的方法分析了不同因素下的吸能效率以及多胞板最优截面类型的选取。结果表明：在面外冲击作用下,泡沫铝填充薄壁铝合金板的破坏模式为对称圆锥式破坏,冲击力-位移曲线和变形图显示其变形过程分为两个阶段：弹塑性变形阶段和回弹阶段;在发生相同位移时,18种不同参数的多胞板,其吸收的总能量(E)和比吸能(SEA)相对于单胞板都提高了400%以上,是一种更具吸能特性的板,可广泛应用于防护工程。     

关于超塑性流动方程的讨论

鉴于通常的超塑性流动方程σ=Kε~m中的m和K都不是常数,本文提出一个改进的流动方程,σ=σ_(ε/ε_0)~m。这一新方程在保持原方程反映材料应变速率敏感效应的基础上,在拟合lgσ-Igε曲线及实际拉伸曲线上均优于原方程。并且新方程能够和变形机理的速率方程协调一致。在现象学上,其参数ε_0和(?)可以分别代表最佳超塑性变形时的应变速率和流变应力。     

球形孔通孔和闭孔泡沫铝合金的超声衰减性能

研究了球形孔通孔和闭孔泡沫铝合金在1 MHz～10 MHz的超声衰减性能.结果表明:泡沫铝合金的超声衰减性能决定于其孔结构;通孔泡沫铝合金的超声衰减系数α随着孔径d的减小、孔隙率Ps减小和比表面积Sv的增加而增大;闭孔泡沫铝合金的超声衰减系数α随孔径d的减小、孔隙率Ps的增加和比表面积Sv的增加而增大;当孔径d、孔隙率Ps相近时,闭孔泡沫铝合金的超声衰减性能优于通孔泡沫铝合金;在1 MHz～10 MHz二者是具有良好阻尼性能的轻质材料.其衰减机制为在弹性范围内超声应力波在具有大量孔隙界面的泡沫铝合金中的衰减.     

A study of fabricating and compressive properties of cellular Al–Si (355.0) foam using TiH2

Al–Si (355.0) alloy foam has been produced by Alporas method (in which foam alloy melts, and titanium hydride is used as a blowing agent). Mechanical behavior such as quasi-static compression (strain–stress curves, energy absorption capacity), also the effects of thermal properties on the macroscopic structure of the produced foam were investigated. In addition, the effect of energy absorption capacity on percentage porosity has also been studied. The research shows that the produced foam with an average cell size and proper distribution has a more mechanical stability compared to the foams with no such characteristics. It was found that yield strength tends to increase from 12.51 MPa for porosity 74.0% to 22.32 MPa for porosity 54.0%. This foam has also been compared with other foams such as Al-pure foam and Mg foam. It can be stated that Al–Si (355.0) foam has a higher yield strength in comparison to Al-pure foam and Mg foam.     

Nitridation-assisted Al infiltration for fabricating Al composites

In this study, we developed an Mg-, vacuum-, and pressure-free process for manufacturing Al-based composites via nitridation-assisted spontaneous infiltration of molten Al. In this process, the wettability between molten Al and ceramic reinforcement was significantly enhanced by nitridation via heating and surface modification of the Al particles; this provided a sufficient capillary force (i.e., negative curvature) for spontaneous infiltration of molten Al. The proposed process can generate composites based on Mg-free Al matrices and is relatively versatile in terms of the type, volume fraction, and morphology of the reinforcement material. Furthermore, the properties of the final composites can be modified by controlling their degree of nitridation, thereby expanding the material scope and their corresponding application fields.     

低价硫化铝法从氧化铝直接炭还原制铝的动力学研究

低价硫化铝法从氧化铝直接炭还原制铝的动力学过程极为复杂,过程的前期受界面化学反应控制,过程后期受扩散过程控制,并求得不同时期的活化能,反应前期:E1=63.81 kJ/mol(6.67 Pa)、E2=50.82 kJ/mol(66.7 Pa)、E3=54.72 kJ/mol(666.7 Pa)、E4=39.61 kJ/mol(1333 Pa);反应后期:E*1=112.90 kJ/mol(6.67 Pa)、E*2=89.92 kJ/mol(66.7 Pa)、E*3=97.32 kJ/mol(666.7 Pa)、E*4=51.83 kJ/mol(1333 Pa).从动力学的角度提出了反应的较佳条件.温度、真空度的提高一方面可增大反应速率,但另一方面却加大了硫化铝的挥发,仅从增大速率而言,温度应大于1100 ℃,真空度应优于1333 Pa为宜.     

钪在铝及铝合金中的作用

总结了Sc在铝及铝合金中对合金组织、力学性能、热稳定性、焊接性能和抗腐蚀，性能的影响。Sc在铝合金中是有效的晶粒细化剂、再结晶抑制剂和改善焊接性能的添加剂；Sc可以细化铝合盒晶粒，提高合盒的力学性能和再结晶温度，增强铝合金的热稳定性，改善铝合盒的焊接性能和抗腐蚀性能；分析了Sc在铝合盒中的作用机理。     

Al and Ti/Al contacts on n-GaN

Al(60 nm) and Ti(40 nm)/Al(160 nm) metal layers have been deposited by thermal evaporation onto n-GaN epitaxial layers grown by metal organic chemical vapour deposition (MOCVD) on a c-plane sapphire substrate. The samples have been annealed at 300, 400, 700 or 900 °C for 10 min in vacuum. The microstructural and electrical properties of the contacts have been investigated by electron microscopy, X-ray diffraction and by current-voltage measurements. As-deposited Al and Ti/Al contacts were rectifying with Schottky barrier heights below 0.35 eV and 0.38 eV, respectively. After heat treatment at 300 °C and 400 °C both contacts exhibited linear current-voltage characteristics. After annealing at 700 °C Al contacts became rectifying with a barrier height of 0.42 eV, while Ti/Al contacts remained nearly linear at the same temperature. The electrical characteristics and XRD analysis indicated that the upper metal in Ti/Al contact diffused in the Ti layer already during deposition. Cross-sectional transmission electron microscopy revealed that in the case of Ti/Al contacts, the continuity of the Ti layers ceased when annealing above 700 °C. X-ray diffractions showed, that a Ti₂N interface phase formed in Ti/Al contacts at 700 and 900 °C, and an AlN interface phase developed in the same contact at 900 °C.     

Thermal stability of Al/Al11 Ce3 and Al/Al11 La3 /Al3 Ni eutectics obtained by Bridgman growth

Abstract

The effects of extended treatment at 500°C on microstructure and microhardness of Al/Al₁₁ Ce₃ and Al/Al₁₁ La₃ /Al₃ Ni eutectics in Al–12·1Ce and Al–11·3La–5·4Ni (wt-%) alloys Bridgman solidified at 0·1 mm s^-1 are reported. Coarsening of Al/Al₁₁ Ce₃ occurs more rapidly in some eutectic cells than others such that areas coarsening at a lower rate still form 10% of the microstructure even after 3024 h. It was found that Al/Al₁₁ La₃ /Al₃ Ni showed accelerated coarsening at eutectic cell boundaries but association between Al₁₁ La₃ and Al₃ Ni still remained within cells and at cell boundaries even after 3024 h. Associated decreases in hardness for Al/Al₁₁ Ce₃ were similar to fibrous Al/Al₆ Fe of similar initial spacing subjected to the same heat treatment. The 30% higher initial hardness of Al/Al₁₁ La₃ /Al₃ Ni largely persisted even after 3024 h at 500°C.     

Transport Properties of the Tunnel Junctions Al1-xCox/{Al1-xCox-oxide}/Al

The oxides of Al1-xCox (x=0,0.25,0.5,0.75, and 1.0) alloys were chosen as barrier materials in this work. The tunnel junction consists of the bottom electrode Al1-xCox and the top electrode Al with an insulating layer { Al1-xCox-oxide} which was formed by natural oxidation in a baking-box at 333K. The oxidation time for forming an Al1-xCox-oxide layer on the surface of the bottom Al1-xCox layers were optimized.The resistance of Al1-xCox/{ Al1-xCox-oxide}/Al tunnel junctions varied between 101 and 106 Ω measured at 1 my and 4.2 K. The effective barrier height and width of insulating layers Al1-xCox-oxide ( x=0.25, 0.5, and 0.75 )varied between 0.6 and 2.7 eV and between 1.3 and 2.1 nm. It is shown that the thin oxide layer of Al1-xCox alloys can be chosen as barrier materials.     

铝合金时效成形及时效成形铝合金

介绍了铝合金时效成形的方法、基本原理、工艺特点及应用情况,概括了国外研究铝合金时效成形工艺及相关可时效成形铝合金的现状,重点阐述了时效成形对铝合金微观组织结构的影响.