富铈混合稀土对工业纯铝中富铁相形貌的影响

研究了不同含量富铈混合稀土变质对含w(Fe)=2%的工业纯铝中富铁相组织形貌的影响。结果表明,w(Fe)=2%的工业纯铝中富铁相呈长针状或蠕虫状,添加稀土使该工业纯铝中的富铁相Al3Fe由长针状变为弥散细小的颗粒状。随着稀土含量的增加,α-Al晶粒逐渐得到细化,Al3Fe尺寸及数量不断减小。添加w(RE)=0.5%的稀土时,α-Al晶粒细化效果最佳,而且富铁相呈细小的颗粒状均匀分布在α-Al基体晶界处。     

Fe、Si对工业纯铝晶粒细化的影响

通过AlTiB晶粒细化剂对高纯铝、工业纯铝的细化及Al-10Ti中间合金、Fe、Si对工业纯铝的细化，研究了Fe、Si在工业纯铝晶粒细化过程中的作用。试验结果表明，0.3％的AlTiB晶粒细化剂对工业纯铝有良好的细化效果，但不能细化高纯铝；Fe、Si作为晶粒细化剂单独加入时，有不同程度的细化作用。分析认为，Fe、Si在工业纯铝晶粒细化过程中有双重作用，即促进型壁晶核的游离和增加α-Al在型壁形核的质点数目。     

单独或复合添加Al-5Ti-B、Mn和Sn对A356铝合金滑动磨损性能的影响(英文)

研究添加Al-5Ti-B、Mn和Sn对A356铝合金滑动磨损性能的影响。采用光学显微镜、扫描电镜和透射电镜观察合金的显微组织和磨损表面。结果表明,Al-5Ti-B晶粒细化的合金具有α(Al)等轴晶组织,比未细化合金具有更好的抗磨损性能。另外,Mn元素的添加能使β-Al5Fe Si转变成α-Al(Mn,Fe)Si相,减少裂纹形成的倾向并提高合金的抗磨损性能。A356合金中添加Sn会形成Mg2Sn相,导致合金不能形成Mg2Si析出强化相;同时软化的β-Sn相会降低合金的硬度并最终降低合金的抗磨损性能。     

微量RE对易拉罐用铝材中富Fe杂质相的变质作用

在易拉罐用铝材熔体中添加微量RE元素对富Fe杂质相进行变质处理，采用扫描电镜（SEM）、X-Ray衍射（XRD）、能谱分析（EDAX）等分析测试手段研究杂质相的变质效果。结果表明：RE聚集于基体晶界，可通过与Al生成富Fe相异质形核核心，影响溶质原子扩散过程和杂质相生长方式，取代富Fe相中部分组成元素以降低x（Fe）/x（Mn）的经值等途径提高富Fe相形核率，并促使其生长形态发生变化，变质效果显著，即晶界处由粗大鱼骨状的Al（Fe,Mn,Si）复合相转变为Al（Fe,Mn,Mg,Si,RE）和Al（Fe,Mn,RE）复合相，分别呈短小骨骼状或小球状，可明显提高该事金的塑性。     

稀土Ce对工业纯铝中富Fe相的球化作用

通过加Ce前后工业纯铝显微组织、力学性能和耐中性盐雾性能的比较以及SEM、EDS等分析,研究了稀土Ce对纯铝中富Fe相的球化作用及其对工业纯铝力学性能和耐蚀性能的影响.结果表明,Ce对纯铝中富Fe相有球化作用,使富Fe相由粗大汉字状变为细小团球状,并与Fe、Si等杂质形成高熔点金属间化合物.通过加Ce变质,使工业纯铝的抗拉强度提高44.18%,伸长率提高32.04%,耐中性盐雾时间延长120%.     

Fe含量对热挤压再生铝合金组织和性能的影响

采用光学显微镜、扫描电镜、万能拉伸机、显微硬度计等手段研究了不同Fe含量对热挤压再生铝合金组织和性能的影响,并探讨富Fe相形态演变机制。结果表明,Fe含量的增加有利于抑制再生铝晶粒尺寸的长大。随着Fe含量增加,晶粒尺寸逐渐减小,减小幅度达25%。热挤压后再生铝中富Fe相发生了折断和破碎,并沿着挤压方向呈带状分布。随着Fe含量增加,富Fe相的面积分数和平均长度均逐渐提高,当Fe含量分别为0.10%~1.24%时,面积分数和平均长度增长最快;而富Fe相的圆整度则随Fe含量的增加稍有降低。同时,再生铝的抗拉强度、屈服强度和伸长率均随着Fe含量的增加呈现逐渐降低的趋势,最大降低幅度分别为10.4%、23.2%和46.0%,而显微硬度则逐渐提高,最大提高幅度为21.7%。断口形貌也由纯韧性断裂转变为混合型断裂模式。     

预退火处理对等通道转角挤压双辊铸轧AA3003铝合金显微组织演变的影响（英文）

添加少量锆元素对双辊铸轧AA3003铝合金进行改性。在450℃对合金进行退火处理产生Al_3Zr析出相,同时出现富Mnα-Al(Mn,Fe)Si相。由等通道转角挤压引起的大塑性变形致使合金的晶粒细化且硬度增加。电子背散射衍射及透射电镜观察结果显示在热处理变形后期预先退火处理对合金显微组织变化的影响。对于变形前未进行退火处理的合金,在450℃退火时,其位错回复和α-Al(Mn,Fe)Si相析出使再结晶提前发生。由于预变形退火使固溶体中Mn原子含量降低,因此,在变形过程中对合金进行预变形退火处理会使回复更容易发生。Al_3Zr析出相能促进再结晶过程的进行。     

Mn/Cr复合变质对15%Mg_2Si/再生A356-1.5%Fe基复合材料中富Fe相形态的影响

利用Mn/Cr复合对15%Mg_2Si/再生A356-1.5%Fe基复合材料进行变质处理,利用SEM、EDS、热分析等方法研究Mn/Cr添加量对复合材料中富Fe相形态的影响规律及其机制,并探讨Mn/Cr添加量对复合材料各物相的凝固结晶特性顺序的影响。富Fe相形态随着Mn/Cr添加量的变化而改变,未变质时,富Fe相形态主要为长针状;Cr(1.0%,质量分数)含量较多时,富Fe相形态主要为骨骼状;Cr和Mn含量均为0.5%时,富Fe相形态主要以颗粒状为主,此时变质效果最佳;而当Mn(1.0%)含量较大时,富Fe相形态则主要呈现花瓣状。未变质复合材料凝固结晶顺序为:初生Mg_2Si相(649.8℃)、α-Fe相(629.8℃)、π-Fe相(618.3℃)、Al+Mg_2Si共晶(578.3℃)、Al+Mg_2Si+Si三元共晶(556.7℃);随着Mn含量的不断增加,富Fe相的初始形核温度与基体形核温度差增大,其形核生长时间增加,Fe相尺寸不断增大,数目相对减少。     

回用铝对6008铝合金挤压型材晶间腐蚀的影响

对添加和未添加回用铝的6008铝合金挤压型材进行晶间腐蚀实验。实验结果表明:回用铝中的化学成分较为复杂,不易被检测,添加了回用铝的铝合金制品中Si、Fe元素含量相对较高,且Al元素整体偏低。铝基体中形成较为弥散分布的含Al、Si、Fe、Mn元素的第二相粒子,在挤压塑性变形过程中和固溶处理过程中有利于抑制再结晶晶粒长大,细化再结晶晶粒。但同时第二相的电极电位较高,与基体中电位较负的Mg_2Si及Al基体形成微电池,加速材料腐蚀速度。     

Mn和Sn对Sr变质、Al-5Ti-B晶粒细化Al-7Si-Mg合金显微组织的影响（英文）

研究Mn与Sn对Sr变质、Al-5Ti-B晶粒细化Al-7Si-Mg合金显微组织的影响。结果表明,合金添加高含量Sr后具有柱状树枝晶结构,Al-5Ti-B晶粒细化剂发生了毒化现象:TiB_2颗粒偏聚在共晶Si区域,并发现Sr金属间化合物在TiB_2颗粒上分布。讨论了Sr毒化现象的机理。此外,添加Mn元素会使合金的富铁相结构从β-Al_5FeSi向α-Al(Mn,Fe)Si转变。随着Mn含量的增加,α-Al(Mn,Fe)Si相从树枝状转变为树枝状分布的小棒状,最终转变为汉字状结构。透射电镜(TEM)观察显示,Mg相对于Si更倾向于与Sn反应,Mg_2Sn在Si/Si界面或Al/Si界面上析出。     

Fe、Si质量比对Al-Mn合金中第二相的影响

采用金相显微镜、扫描电镜和XRD等手段,分析了Fe、Si质量比和冷却速度对AI-Mn系变形铝合金中第二相形貌及类型的影响.结果显示,Fe、Si质量比<2.5时,合金中的第二相化合物为骨骼状α-Al12(Fe,Mn)3Si相,Fe、si质量比2.5时开始形成针状β-AI85(Mn,Fe)14Si相化合物.而冷却速度增大时,促进形成骨骼状的α-AI12(Fe,Mn)3Si相.     

Effect of yttrium on the microstructure of a semi-solid A356 Al alloy

The semi-solid slurry of an A356 Al alloy,which was grain-freed by yttrium,was manufactured by low temperature pouring.The effects of grain-refining on the morphology and the grain size of the primary α phase in the semi-solid A356 Al alloy were researched.The results indicate that the semi-solid A356 Al alloy with particle-like and rosette-like primary α-Al can be prepared by low temperature pouring from a liquid grain-refined A356 alloy.The grain size and particle morphology of primary α-Al in the A356 Al alloy are markedly improved by the addition of 0.5 wt.% Y.The fining mechanism of Y on the morphology and grain size of the primary α-Al in the semi-solid A356 Al alloy was delved.     

Precipitation of partially coherent α-Al(Mn,Fe)Si dispersoids and their strengthening effect in AA 3003 alloy

The orientation relationship (OR) between α-Al(Mn,Fe)Si dispersoids and the Al matrix in AA 3003 alloy has been systematically studied by selected area electron diffraction patterns. New types of ORs between the cubic dispersoids and the cubic matrix phase have been found as 〈1 −1 1〉_p//〈1 −1 1〉_m and {5 −2 −7}_p//{0 1 1}_m. High-resolution transmission electron microscopy and crystal structure simulation studies on the habit planes of dispersoids show that α-Al(Mn,Fe)Si dispersoids are partially coherent with the Al matrix. Precipitation of α-Al(Mn,Fe)Si dispersoids in the alloy has been found to have a strong influence on enhancing both the yield strength and tensile strength of the alloy. The dispersion-hardening effect of the dispersoids has been explained by the Orowan mechanism.     

Effect of heat treatment on microstructures and mechanical properties of A356 alloy cast through rapid slurry formation (RSF) process

The effect of T5 heat treatment on microstructure and mechanical properties of A356 alloy was observed. The as-cast A356 alloy exhibited coarse dendrites and long Si needles. RSF process changed the dendritic α-Al phase to globular morphology which helps in improving the mechanical properties of the alloy. The addition of 0.6wt-% Al–5Ti–1B grain refiner refined the average grain size of primary α-Al phase. T5 heat treatment at 170 °C for 20 h in different processing conditions was given to A356 alloy. T5 heat treatment led to further refinement of α-Al phase and Si needles, precipitation hardening due to Mg₂Si phase and reduction in the porosity level (%). The Quality Index for A356 alloy in different processing conditions was also measured. Results showed that RSF process with the use of baffles, addition of grain refiner and T5 heat treatment had improved the mechanical properties over other processing conditions.     

Effect of Mn on Fe containing phase formation in high purity aluminium

In this study, the effect of varying Mn additions on Fe phase formation in high purity Al and its corresponding effect on the resulting mechanical properties have been investigated. Thermodynamic simulations have shown that in the Al–Fe–Mn ternary system two intermetallic phases (namely Al₆(Fe,Mn) and Al₁₃Fe₄) form. Findings indicated that a relatively high amount (>1 wt-%) of Mn was required to achieve Al₆(FeMn) phase formation which was congruent with experimental results. Both the Al–Fe and Al–Fe–Mn phases observed displayed fibre/platelet type morphologies and were found to exist at α-Al grain/cell boundaries. Results indicate that the Fe phases coarsen with increasing Mn content. In the Al–Fe system the Mn addition improves yield strength (YS) and ultimate tensile strength (UTS) but reduces elongation beyond the reduction resulting from the Fe addition. The further decrease in elongation with Mn was attributed to the increase in volume fraction of the intermetallic phases.     

Mechanism of Exfoliation (Layer Corrosion) of AI-5%Zn-1%Mg

Abstract

The mechanism of exfoliation in AlZn5Mg1 alloy has been studied by making a survey of the phasesb occurring in the alloy in the naturally aged and artificially aged conditions, preparing the phases in pure state and investigating their electrochemical properties. It has beenfound that in the naturally aged alloy, the attack is confined to lamellar zones in the structure giving rise to the exfoliation. Finely dispersed α-Al(Fe, Me)Si phase particles arranged in streaks along the extrusion or rolling direction act as cathodes and the anodic areas consist of narrow zones of the Zn- and Mg-rich matrix, next to the particles. Between the streaks of α-Al(Fe,Me)Si particles, layers of matrix are left unattacked. Since the main factor determining the amount of α-Al(Fe,Me)Si phase is the Fe content, an increase in Fe content will decrease resistance to exfoliation. In the artificially aged condition, the alloy is not prone to exfoliation, but shows a type of general attack. α-Al(Fe,Me)Si particles again constitute the cathodes of the corrosion cells, but the anodic phase is the M-phase (MgZn₂), which is evenly distributed.

Since the zone next to a weld bead is essentially in the solution treated condition, it will become resistant to exfoliation on post-weld artificial ageing. At some distance from the weld bead, however, there will be an ‘over-aged’ zone, where neither the hardness nor the resistance to exfoliation will be very much increased on artificial ageing. This is due to the formation of especially wide precipitate-free zones around α-Al(Fe,Me)Si and E-phase particles and around grain boundaries on ‘over-ageing’. Since the precipitate-free zones are due to vacancy depletion, these zones are supersaturated with respect to Zn and Mg and thus prone to corrosion. The attack will be confined to the matrix, especially along streaks of α-Al(Fe,Me)Si and E-phase particles.     

离心铸造铝铁基梯度功能材料的组织形态及控制

在离心力场下，使初生金属间化合物沿离心半径呈梯度变化，制备出Ａｌ－Ｆｅ梯度功能材料，并在合金中加入适量的Ｓｉ，ＲＥ，Ｍｎ合金元素，改善了初生金属间化合物的形态，使针状或片状初生相变为球状、汉字状，从而有利于力学性能的提高。     

Formation and characterisation of a chromate conversion coating on AA6060 aluminium

AA6060-T6, an AlMg0.5Si0.4 model alloy and α-Al(Fe,Mn)Si phase electrodes have been subjected to chromate treatment in a commercial chromate-fluoride based solution. The coated surfaces were subsequently examined by use of field emission SEM, TEM, AES and electrochemical measurements in 0.1 M NaCl solution in order to study the effect of substrate microstructure on coating formation and properties. Non-uniform growth of the chromate conversion coating (CCC) on AA6060-T6 resulted in a porous morphology, with cracks extending down to the base metal. Poor coverage was particularly observed at the grain boundaries. The thickness of the CCC after completed treatment was about 150-200 nm, while significantly thinner films were formed on the α-Al(Fe,Mn)Si particles. AlMg0.5Si0.4 in the artificially aged (T6) condition exhibited a coating morphology similar to AA6060-T6, while CCC formation on homogenised AlMg0.5Si0.4 was characterised by growth of localised oxide particles and filaments, resulting in poor coverage. These observations indicated that precipitation of Mg₂Si particles due to heat treatment promoted nucleation of the CCC. Chromate treatment caused a significant reduction of cathodic activity on AA6060 during subsequent polarisation in chloride solution. This was attributed to rapid formation of a thin chromium oxide film on the α-Al(Fe,Mn)Si particles during the chromate treatment, resulting in significant cathodic passivation of the phase. Inhibition of the oxygen reduction reaction at cathodic intermetallic particles is suggested as an important factor contributing to the high performance of chromate pre-treatments on aluminium.