杂质含量对Al—Fe合金加工软化规律的影响

研究了杂质含量Ａｌ－２．０％Ｆｅ合金加工软化规律的影响。结果表明，杂质含量较低（０．００４％）的Ａｌ－Ｆｅ合金，在６０％以上轧制率时出现加工化现象：杂质含量增加（０．０４％）时，在轧制率高达９０％以上方出现加工软化；而杂质含量较高（０．４％）的Ａｌ－Ｆｅ合金在轧制过程中没有出现加工软，     

Al-Si合金铸铁抗锌液腐蚀的研究

研究了不同Ａｌ含量的Ａｌ－Ｓｉ合金铸铁在热浸锌过程中的腐蚀速率、界面组织结构和成分变化。结果表明,随着合金铸铁中Ａｌ和Ｓｉ含量升高腐蚀速率降低,当Ａｌ－Ｓｉ总量为１０（ｗｔ）％时,腐蚀速率小于普通灰铁的１０％。Ａｌ－Ｓｉ合金铸铁锌液腐蚀的原因：（１）表层形成较稳定的Ｆｅ３Ａｌ、ＦｅＡｌ或Ｆｅ３Ｓｉ、Ｆｅ５Ｓｉ３相;（２）界面层中形成较厚的合金相层;二者均使铸铁与锌液反应扩散速率降低。另外,石墨与基体的边界为Ｚｎ原子的侵入提供了通道,温度越高浸蚀越重。在同样的化学成分条件下,球状或蠕状石墨铸铁优于片状石墨铸铁的抗蚀性。     

快速凝固Al-Fe基合金的组织演化和相选择

对Ａｌ－７．８３Ｆｅ,Ａｌ－５．１６Ｆｅ（ｗｔ％）两种Ａｌ－Ｆｅ快凝条带中不同冷速部位组织进行了ＴＥＭ分析,着重考察了Ａｌ－Ｆｅ快凝合金的组织演化演化及其各竞争初生相的析出次序。结果表明,Ａｌ－Ｆｅ合金快凝组织与成分及熔体的冷速有关,对一定成分的合金,当增加其熔体冷速时,亚稳ＡｌｍＦｅ相优先于Ａｌ６Ｆｅ相析出,初生α－Ａｌ相优先金属间化合物相析出,当合金中Ｆｅ含量越低,形成无一金属间化合物的相单－     

用透射和扫描电镜观察Ni—Cr—Al合金γ‘和Cr（α）析出相

Ｎｉ－Ｃｒ－３％Ａｌ－０．２％Ｃｅ合金０．３ｍｍ细丝经５００－６００℃时效处理，用透射和扫描电镜观察组织形貌，用化学定量提取法和测定微区成分的方法确定相Ｎｉ、Ｃｒ、Ａｌ的含量，用程控图像仪测定富Ｃｒ（α）相析出颗粒大小和分布，查明了γ相沿基体９１００）面共格析出并细小颗粒状，在γ相周围析出的过饱和富Ｃｒ（α）相弥散分布在合金基体中，据此认为该合金是由γ相和富Ｃｒ（α）相复合析出强化合金基体的。     

微量Y对铸造Ni50Al20Fe30合金组织与性能的影响

研究了不同Ｙ含量对铸造Ｎｉ５０Ａｌ２０Ｆｅ３０合金与性能的影响。结果表明,微量Ｙ的加入可以改善Ｎｉ５０Ａｌ２０Ｆｅ３０合金的强强度与塑性。Ｙ含量为０．０５ｗｔ％－０．１ｗｔ％是合金最佳含量范围。微量Ｙ的加入影响合金的共晶区,可明显改变合金的微观组织形态。     

快凝粉末Al-10Fe-1V-2Si-0.5Re耐热铝合金

研究了用超声雾化法制备的快凝粉末Ａｌ－１０Ｆｅ－１Ｖ－２Ｓｉ－０．５Ｒｅ合金的性能及显微组织。结果表明，合金中弥散相，如α－Ａｌ１２（Ｆｅ．Ｖ）３Ｓｉ相在５００℃仍保持较好的稳定性；合金具有良好的室温和高温性能，其室温抗拉强度为５４７ＭＰａ，延伸率达１１％；合金经过３００℃／１００ｈ热暴露后在３００℃的屈服强度仍达２５０ＭＰａ。     

超负磁致伸缩晶体Sm－Fe、Sm－Dy－Fe和Sm－Dy－Fe－Al的研究

本文研究了轻稀土负磁致伸缩ＳｍＦｅ＿ｘ（１．４０＜ｘ＜１．９４），Ｓｍ＿ｘＤｙ＿（１－ｘ）Ｆｅ＿ｙ（０．８４＜ｘ＜０．９２．１．８０＜ｙ＜１．９０），Ｓｍ＿（０．９０）Ｄｙ＿（０．１０）（Ｆｅ＿（０．９５）Ａｌ＿（０．０５））＿（１．８０）晶体的制备、热处理及磁学性能，发现ＳｍＦｅ＿ｘ合金的λ－ｘ曲线存在两个峰值，峰值的ｘ点随热处理发生的变化有一定的规律性，还比较了热处理前后，Ｓｍ－Ｆｅ、Ｓｍ－Ｄｙ－Ｆｅ和Ｓｍ－Ｄｙ－Ｆｅ－Ａｌ的相组成对性能的影响。热处理用于改善磁致伸缩性能，并且制得了高磁致伸缩性能的ＳｍＦｅ＿２和（Ｓｍ，Ｄｙ）Ｆｅ＿２合金。     

汽车用热镀锌板Fe—Al合金层的研究

用Ｘ射线衍射，萃取碳复型样品的电子衍射等方法对汽车用热镀反Ｆｅ－Ａｌ合金的组织结构进行了分析，结果表明，当锌液中的Ａｌ浓度小于０．１５％时，Ｆｅ－Ａｌ层主要由Ｆｅ２Ａｌ５金属间化合物组成。     

应用量子化学研究Ca2Fe2—xAl2O5的水化活性

用量子化学ＳＣＣ－ＤＶ－Ｘα方法分析了Ｃａ２Ｆｅ２－ｘＡｌｘＯ５体系听ａ２Ｆｅ２Ｏ５，Ｃａ２Ｆ３１．４３Ａｌ０．５７Ｏ５和Ｃａ２Ｆ３１．２８Ａｌ０．７２Ｏ５，认为它们的水化活性随Ａｌ的增加而提高的原因是：（１）Ａｌ的净电荷比Ｆｅ高，易吸收水分子的弧对电子；（２）Ａｌ－Ｏ键比Ｆｅ－Ｏ键弱，易断裂而容易与水反应。     

Fe—40Al及其含Mn或Ti合金的Mossbauer谱

用Ｍｏｓｓｂａｕｅｒ谱研究了Ｂ２结构金属间化合物Ｆｅ－４０Ａｌ及其加Ｍｎ或Ｔｉ量分别为１，５，１０ａｔ．－％的合金．在室温下，Ｆｅ－４０Ａｌ及其合金的Ｍｏｓｓｂａｕｅｒ谱均接近单峰谱线，Ｆｅ原子无明显磁矩对加入第三组元的Ｆｅ—４０Ａｌ合金的Ｍｏｓｓｂａｕｅｒ谱用最小二乘法拟合为两条洛仑兹曲线之和，认为Ｍｎ原子既占据Ｆｅ原子位置，也占据Ａｌ原子位置；而Ｔｉ原子优先占据Ｆｅ原子位置，超过５ａｔ．－％时，才有少量Ｔｉ原子占据Ａｌ原子位置．     

Microstructural evolution of silicon carbide/aluminum oxide composites processed by melt oxidation

The nucleation and growth mechanisms during high temperature oxidation of liquid Al-3 wt% Mg and Al-3 wt% Mg-7 wt% Si alloys were studied to provide a better understanding of the composite fabrication process, especially in the presence of SiC reinforcement. Al2O3-matrix composites with and without SiC particulates have been produced by directed oxidation of aluminum alloys. The microstructure consists of three interpenetrating phases: the SiC preform, a continuous -Al2MO3 matrix, and a network of unoxidized metal. The volume fraction of metal within the oxidation product decreases with increasing processing temperature. The preform does not show any evidence of degradation by the molten alloy, but the growth front tends to climb up the particles, increasing the oxidation area and therefore enhancing the rate of composite growth. The amount of porosity was found to increase with the Mg content in the alloy, from 2.0 vol% for 0.5 wt% Mg to 5.8 vol% for 3 wt% Mg. The role of magnesium and silicon in the growth process are discussed.     

Evolution of Microstructure and Texture during Hot Deformation of a Commercially Processed Supral100

The microstructure and texture in a commercially processed Al-6 wt% Cu-0.4 wt% Zr(Supral100) aluminium alloy have been investigated after annealing and hot tensile straining at 450 ℃,using a field emission gun scanning electron microscope(SEM) and electron backscatter diffraction(EBSD).The microstructure of commercially processed alloy had a relatively large fraction of high angle grain boundaries(HAGBs) which were aligned parallel to the rolling direction,and a strong texture.Annealing at 450 ℃ led to an increase in the fraction of HAGBs and to an increase in HAGB spacing and these changes were progressively enhanced by subsequent tensile deformation.The increasing fraction of HAGBs was due to the annihilation of low angle grain boundaries(LAGBs).A sharpening of texture during annealing was attributed to preferential textural growth,and the reduction of texture at higher tensile strains led to the development of superplastic behaviour.The present work supports the view that the evolution of the fine grain microstructure during the high temperature straining of Supral100 is primarily due to the accumulation of a large area of grain boundary during the initial thermomechanical processing,and does not involve any unusual restoration processes.     

浇注温度对定向凝固Al－Cu合金热裂的影响

针对空心叶片类定向凝固铸件存在的热裂问题，开展了定向凝固热裂规律的研究。本文选择凝固参数较全的Ａｌ－Ｃｕ系合金，研究了定向凝固工艺参数之一的浇注温度对Ａｌ－０．６ｗｔ％Ｃｕ和Ａｌ－２．０ｗｔ％Ｃｕ合金热裂的影响。定向凝固热裂试验表明，提高浇注温度可以降低Ａｌ－０．６ｗｔ％Ｃｕ合金的热裂程度，但对Ａｌ－２．０ｗｔ％Ｃｕ则无作用。理论分析认为，合金在不可补缩区的冷却速率变化是改变合金热裂程度的重要因素。     

The effect of hot-rolling on chill-cast Al,Al-2 wt % Ni and Al-4 wt % Ni alloys

The effect of hot-rolling on the mechanical properties and microstructure of directionallysolidified hypoeutectic Al-Al₃Ni alloys has been studied. Chill-cast hypoeutectic alloys were produced by casting into pre-heated mild-steel moulds placed on copper chills. The chill-cast Al-2 wt% Ni and Al-4 wt% Ni hypoeutectic alloys can be hot-rolled at 500 C to reductions of greater than 95%. Deformation is achieved by deforming the aluminium-rich dendrites in the rolling direction, followed by interpenetration of the Al₃Ni fibres into the dendrites resulting in a homogeneous microstructure. The variations of room-temperature tensile properties for the chill-cast hypoeutectic alloys were measured as a function of reduction of thickness during hot-rolling. The ultimate tensile strength and yield strength increase during rolling because of increasing Al₃Ni fibre alignment, homogeneous dispersion of the Al₃Ni fibres throughout the Al matrix, and work hardening in the Al matrix. The as-chill-cast alloys have strengths which agree with the composite law of mixtures for a combination of Al dendrites and Al-Al₃Ni eutectic. After hot-rolling, the alloy strengths can be predicted from discontinuous fibre reinforcement theory.     

Ti-6Al-4V合金表面超声振动滚压强化研究

采用超声振动滚压加工技术对Ti-6Al-4V合金表面进行处理,探究该项技术对Ti-6Al-4V合金表面质量的影响。通过对该工艺加工前后的Ti-6Al-4V合金进行表面粗糙度参数、XRD图谱、截面微观形貌、表层残余应力及显微硬度的对比分析,结果表明:经该工艺处理后的合金表面各项粗糙度参数皆有明显降低;加工后的合金表面XRD图谱的衍射峰减弱且宽化,衍射角向高角度方向偏移;加工后的合金表层β相组织相较加工前明显细化,且随着深度增加β相组织逐渐增大;在距离表面约50μm位置的残余应力值最大可达到-967 MPa;加工后的合金表面显微硬度可达到421HV,且在0~140μm的深度范围内,显微硬度随着深度的增加逐渐减小至与基体硬度一致。经超声振动滚压加工后的Ti-6Al-4V合金表面质量显著提高,有利于提高其零部件的使用性能。     

The effects of magnesium additions on the structure and properties of Al-7 Si-10 SiCp composites

The additions of magnesium to an aluminium alloy matrix, which contains insufficient magnesium, was found to be essential during the synthesis of composites by the stir-casting technique. Magnesium promotes interfacial wetting between the dispersoid surface and the matrix. Dispersion of SiC_p in Al-7 Si-0.3 Mg (356) alloy matrix without agglomeration and rejection was not possible. Hence, the addition of up to 3 wt% Mg was made to the alloy matrix during the dispersion of 10 wt% SiC_p (34 m), and the microstructure and mechanical properties of the composites were investigated with a view to optimize the magnesium content. With a magnesium content less than 1 wt% in the matrix, the SiC_p particles were essentially in agglomerated form. The highest UTS of 280–300 MPa was obtained with 1 wt% Mg content and SiC_p was uniformly distributed in the matrix. A higher magnesium content (>1.0 wt%) did not further improve the uniformity in the dispersion of SiC_p but the ultimate tensile strength properties deteriorated. This decrease in strength was attributed to the observed coarseness of the Mg₂Si phase, the precipitation of Mg₅Al₈ phase and the presence of a higher amount of porosity in the composites in the heat-treated condition. The aspect ratio (length/width) of precipitates changed from 1–3 for 1% Mg to 3–9 for 3.2% Mg in the matrix. Corresponding values for per cent porosity were 2% and 6%, respectively.     

Effect of Cu addition on microstructures and tensile properties of high-pressure die-casting Al-5.5Mg-0.7Mn alloy

In this study, Cu was added into the high-pressure die-casting Al-5.5Mg-0.7Mn (wt%) alloy to improve the tensile properties. The effects of Cu addition on the microstructures, mechanical properties of the Al-5.5Mg-0.7Mn alloys under both as-cast and T5 treatment conditions have been investigated. Additions of 0.5 wt%, 0.8 wt% and 1.5 wt% Cu can lead to the formation of irregular-shaped Al₂CuMg particles distributed along the grain boundaries in the as-cast alloys. Furthermore, the rest of Cu can dissolve into the matrixes. The lath-shaped Al₂CuMg precipitates with a size of 15–20 nm × 2–4 nm were generated in the T5-treated Al-5.5Mg-0.7Mn-xCu (x = 0.5, 0.8, 1.5 wt%) alloys. The room temperature tensile and yield strengths of alloys increase with increasing the content of Cu. Increasing Cu content results in more Al₂CuMg phase formation along the grain boundaries, which causes more cracks during tensile deformation and lower ductility. Al-5.5Mg-0.7Mn-0.8Cu alloy exhibits excellent comprehensive tensile properties under both as-cast and T5-treated conditions. The yield strength of 179 MPa, the ultimate tensile strength of 303 MPa and the elongation of 8.7% were achieved in the as-cast Al-5.5Mg-0.7Mn-0.8Cu alloy, while the yield strength significantly was improved to 198 MPa after T5 treatment.     

Effect of restoration on hot ductility of high alloy and duplex stainless steels

Abstract

The effect of restoration on the hot ductility of two high alloy austenitic stainless steels and one ferritic–austenitic stainless steel was investigated by means of hot rolling and stress relaxation testing. Cracking tendency was assessed on the basis of the length of the cracks formed. It was found that the recrystallisation kinetics of the high alloy steels is relatively slow, so only partial softening can occur between rolling passes. In the ferritic–austenitic steel the restoration is fairly fast, so softening can be completed between hot rolling passes. The cracking tendency of the steels in the as cast condition increases with increasing pass strain and temperature, but it is negligible in rolling of the steels in the as wrought condition and also minimal in rolling of the as cast steels when using a small strain of 0.1 in the first pass. On the basis of these results, it can be concluded that the cracking problems in these steels are present in the cast structure only. The hot ductility of even partially recrystallised material is perfectly adequate. Hot ductility improves nearly independently of the degree of static recrystallisation, which indicates that ductility is controlled mainly by the grain or phase sizes, not by recrystallisation itself.     

Microstructural characterizations and mechanical properties of NbB2 and VB particulate-reinforced eutectic Al-12.6 wt% Si composites via powder metallurgy method

Mechanical alloying of elemental Al, Si, NbB₂ and VB powder mixtures constituting the matrix alloy composition of Al-12.6?wt% Si and particulate-reinforced compositions of Al-12.6?wt% Si-x NbB₂ and Al-12.6?wt% Si-x VB (x?=?1, 2 and 5?wt%) were carried out for 2, 4 and 8?h in a high-energy ball mill. Mechanically alloyed (MA’d) powders were subjected to cold pressing (450?MPa), cold isostatic pressing (400?MPa) and pressureless sintering (570?°C/2?h) processes. Powder particle morphologies changed from flaky to equiaxed shape after the optimum MA duration of 4?h. 1?wt% NbB₂ and 1?wt% VB particulate-reinforced Al-12.6?wt% Si based composites exhibited better mechanical properties than the Al-12.6?wt% Si matrix alloy and Al-12.6?wt% Si-x NbB₂ and Al-12.6?wt% Si-x VB (x?=?2 and 5?wt%) composite samples. In particular, Al-12.6?wt% Si-1?wt% NbB₂ had the highest yield strength (378?MPa), compressive strength (491?MPa) and hardness (1.86?GPa) values. Investigations on the wear behaviors of the composites revealed that significant amount of wear loss occurred as a result of debris formation due to pull-outs of reinforcing boride (NbB₂ and VB) and oxidized Al (Al₂O₃) particles.     

The effect of alpha phase on flow softening and deformation of Ti–10V–2Fe–3Al

The subtransus deformation behaviour of Ti–10V–2Fe–3Al alloy was investigated. The flow stress curves are featured with significant flow softening, resulting from the breaking up and globularisation of lamellar α phase. The critical major axis of α phase to cause flow softening is 1?µm. Alpha phase acts as a dislocation barrier in the beginning and suppresses the recrystallisation of beta matrix. Dynamic recovery is the main restoration mode for beta matrix and alpha phase just works as a marker of it. Beta phase is dominated by strong {001} and weak {111} orientations. The Burgers relationship and variant selection are observed between α phase and β matrix in a single grain and overall samples, and the subtransus deformation does not destroy it.