Effect of deformation temperature on microstructures and properties of 7075/6009 alloy

The 7075/6009 aluminum composite ingot with the diameter of 65 mm was prepared by double-stream-pouring continuous casting. The deformation behavior and the mechanical properties of the composite ingot compressed at 543, 573, 623, 673 and 723 K were analyzed. The results show that the gradient distributions of composition and hardness in the transition layer of the composite plates still exist after plastic deformation of the ingots. Meanwhile, the thickness of the transition layer reduces from millimeter order to micrometer order. The mechanical properties of the composite plate increase with the increase in deformation temperature from 543 K to 673 K. The best mechanical properties of the 7075/6009 aluminum composite are: σ_b=381 MPa, σ_0.2=322 MPa and δ=16.6%. The appropriate deformation temperature range is (0.75–0.85)T_M, where T_M is the melting point of 7075 alloy.     

打底层对铝合金表面GLC镀层组织和摩擦学特性的影响

采用非平衡磁控溅射离子镀技术在铝合金表面分别制备了以Cr和Al为打底层,Cr-C和A1-Cr-C为过渡层的Cr/Cr C/类石墨碳(GLC)和Al/Al-Cr-C/GLC复合镀层,并与无打底层制备GLC镀层对比,系统研究了不同镀层微观结构、膜基结合力及摩擦学性能,结果表明,铝合金基体表面Cr打底层呈柱状晶生长,Cr/C过渡层无柱状晶特征,且随过渡层增厚,富Cr区域减少,实现了成分的梯度变化:A1打底层与铝合金基体间为一个整体,没有明显界面;Al Cr-C过渡层的成分也呈梯度变化;采用不同打底层和过渡层时.GLC层均为非晶态结构.较无打底层制备GLC镀层,Cr/Cr-C/GLC和Al/Al-Cr-C/GLC复合镀层与铝合金基底间的膜基结合力显著增强,以Al为打底层的复合镀层的失效临界载荷最大.磨损实验中,在不同载荷条件下2种复合镀层均具有低的摩擦系数.     

铝合金/合金钢异种金属摩擦焊接头组织与性能

针对油气资源勘探开发用钻杆轻量化的需求,以小尺寸试棒7075-T6铝合金和37CrMnMo合金钢利用连续驱动摩擦焊技术实现连接,探索开发铝合金/合金钢轻量化复合钻杆焊接制造的可能性和可行性,研究了焊接工艺参数对接头成形、微观组织及力学性能的影响.结果表明,接头界面铝侧的晶粒受到力和热的作用发生完全动态再结晶,而在热力影...     

Wear of Al/Al3Zr functionally graded materials fabricated by centrifugal solid-particle method

In this study, Al–5mass%Zr functionally graded materials (FGMs) were fabricated by the centrifugal solid-particle method (CSPM) under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction showed that Al₃Zr platelet particles are almost oriented normal to the applied centrifugal force direction. Volume fraction of Al₃Zr particles increases close to the ring surface. Moreover, this distribution range of Al₃Zr particles becomes broader with decreasing the applied centrifugal force. The wear anisotropy of the fabricated Al/Al₃Zr FGMs was strongly influenced by the platelet particles orientation at the test position. Investigating both of the worn surface morphology and the sub-worn surface layer showed that plastic deformation induced wear is the dominant mechanism during the wear process of Al/Al₃Zr FGMs samples. Therefore, some of the tested samples were severely deformed and an Al₃Zr particles-free layer containing Al–Zr supersaturated solid solution was observed very near to the worn surface during the wear test.     

Titanium diboride-metals gradient materials prepared by field activated diffusion bonding process

Functionally gradient samples are prepared by getting metal Ni or Cu bonded with Ni-matrix composites reinforced by TiB_2 particles by field activated diffusion bonding process.The intermetallic compound of Ni_3Al has been applied as a mediate layer in order to reduce residual stress.The microstructure,phase composition of the interfaces between the metal and Ni_3Al are determined and the mechanical properties of the gradient materials are characterized.Elemental concentration profiles across the interfaces between layers showed significant diffusion dissolution and formation of firm bonds.Measured micro-hardness values of the sample increased monotonically from the metal substrate to the surface layer of composites.The values for the surface composite layer ranged from about 2 000 HK to 3 300 HK.The results of this investigation demonstrate the feasibility of field activated diffusion bonding process for rapid preparation of FGMs.     

离心铸造自生Zn—Al—Si表面复合材料的组织与性能

采用热膜金属型离心铸造Zn-27Al-5Si合金,获得了内层含大量初晶Si,外层有少量初晶Si,中层为细小共晶Si的表面复合材料,考察了复合材料的组织形貌和复合材料的,吧及模温和转速对组织的影响。结果,随着模温的提高,初晶Si、共晶Si和基体组织变得粗大;随着模转速的增加,初晶Si在内侧富集层厚度减小,初晶Si面积比增大。复合材料的内层由于聚集了大量初晶Si而具有较高的硬度和较优的耐磨性。复合材料的断裂方式为脆性断裂,含共晶Si的中层在断裂中比含块状初晶Si的内层经历了更多的塑性变形。     

铸态2219铝合金热压缩变形组织演变规律

为解决2219铝合金微观组织粗大、第二相分布不均的问题,开展了对铸态2219铝合金热压缩变形组织演变规律的研究。研究结果表明,经热压缩变形后,铸态2219铝合金组织中粗大的晶粒及连续网状分布的残余结晶相被打碎,经热处理后形成了均匀的再结晶组织。随着变形温度的升高,晶粒组织粗化,但Al2Cu相的分布更细小、均匀;随着变形量的增大,晶粒组织逐渐细化,晶粒大小分布也更均匀,且Al2Cu相也随变形量的增加破碎得更充分,分布更细小、均匀。在大直径铸锭锻造开坯过程中,为了获得Al2Cu相细化分布的组织,变形温度应控制在420℃以上,单次变形量不应低于50%。延长锻后保温时间不会显著影响材料的显微组织,因此,在锻造开坯过程中,为了保证合理的变形温度区间,可以采用回炉加热多火次锻造的方式。     

WC/高铬铸铁渗层组织的研究

介绍了铸渗工艺的发展及机理,分析了铸渗外层组织、中层组织、内层组织的形成原因,指出:(1)铸渗层组织由表层的合金烧结层、内层的钎焊层、界面的熔合层三个区域构成;(2)浇注温度对复合层的质量有显著的影响,当浇注温度在1 540～1 580℃、增强颗粒的粒度在60～80目之间时,复合层的综合质量较为理想;(3)由于铸渗层存在(Fe,Cr)7C3、Cr7C3、WC等组织,耐磨性能大大提高;(4)从复合层到基体显微硬度呈梯度分布,显微硬度值先升高后降低,硬度的梯度分布使复合层的强度与基材的韧性得到充分的利用。     

直接水冷半连续铸造制备4045/3004/4045铝合金三层复合锭

采用直接水冷半连续铸造法制备 4045/3004/4045 铝合金三层复合锭坯。考察复合界面附近的温度场分布,并研究复合界面的宏观形貌、微观组织及界面两侧的成分分布。结果表明,在冷却板的作用下,界面附近形成一层具有一定厚度的半固态层,从而保证半连续铸造过程制备复合锭坯的顺利实现。两种合金在界面处较好地冶金结合在一起。界面力学性能测试结果表明,复合界面的抗拉强度和剪切强度分别为 105 和 88 MPa,这进一步证明了复合界面的结合是一种冶金结合。     

等离子喷涂NiAl-Al2O3梯度陶瓷涂层的性能研究

利用等离子喷涂方法制备了NiAl-Al2O3梯度陶瓷涂层,并对涂层的组织分布、结合强度、显微硬度和抗热震性进行了试验研究.结果表明:梯度涂层的组织表现出宏观的不均匀性和微观的连续性的分布特征;NiAl金属间化合物过渡层的引入可有效地改善涂层的质量;在Al2O3质量分数为80%附近涂层的显微硬度最高;涂层成分的梯度化有利于涂层的结合强度和抗热震性能的提高.     

铁基粉末冶金件双层辉光等离子Cr-Mo共渗研究

采用双层辉光等离子技术在对粉末冶金材料FN0205进行等离子烧结的同时在其表面进行Cr-Mo共渗处理.达到烧结效果的同时在试样表面得到合金渗层,渗层表面Cr含量达到10%左右,Mo含量达到5%左右.渗层厚度达到68 μm.合金渗层表面物相由Fe、Fe-Cr、Cr23C6、Cr7C3、Mo2C组成.渗层表面显微硬度达到7...     

挤压复合铸造7075/6061双金属铸锭的界面组织与性能

采用挤压复合铸造工艺制备出具有“半固态组织/枝晶组织”分布特征的7075/6061包覆型双金属复合铸锭,并对复合铸锭界面处的组织及硬度进行了分析。结果表明,界面结合良好,为冶金结合,无杂质和氧化皮存在。界面处组织过渡平缓,7075铝合金固相颗粒呈一定规律性分布;除Zn元素浓度呈明显梯度变化外,其它合金元素分布较均匀。界面大部分由较细小等轴晶组成,且有大量合金元素沉积在晶界处,致使界面处硬度高于两侧金属,硬度最高达63.3 HRB。     

Effect of Radial–Shear Rolling on the Formation of Structure and Mechanical Properties of Al–Ni and Al–Ca Aluminum–Matrix Composite Alloys of Eutectic Type

Results of an analysis of the mechanical properties and macro- and microstructures and the fractographic analysis of the fractures of samples of the Al–6 wt % Ni and Al–7.6 wt % Ca aluminum–matrix composite alloys of eutectic type after thermomechanical treatment, including radial–shear rolling (RSR),—have been presented. The hot deformation of preliminarily annealed ingots of studied alloys with a circular section 60 mm in diameter using RSR method at 400–450°C with total reduction μ = 9.0 can lead to the formation of the gradient microstructure with external more deformed layer characterized by high microhardness and thickness of about 1.5–2.5 mm. The microhardness decreases smoothly from the periphery to the center of samples. Uniaxial tensile tests revealed that the strength of alloys after RSR increases by 2.0–2.5 times compared to the as-cast or the annealed state, the plasticity is the same as in the annealed state or increases by several times as in the case of the Al–7.6 wt % Ca alloy. The latter fact is clearly illustrated by the results of the analysis of the fractures of samples, for which the transition from the brittle or mixed type of the fracture before deformation treatment to the pronounced ductile dimpled type after RSR has been observed.     

激光熔注制备Al-Cr/7075Al梯度复合涂层的性能

采用激光熔注技术在7075铝合金表面制备了Al-Cr/7075Al梯度复合涂层。采用扫描电镜(SEM)、能谱仪(EDS)和X-射线衍射(XRD)和显微硬度计等研究了复合涂层的微观结构、物相及显微硬度。结果表明:Al-Cr/7075Al梯度复合涂层与基板结合良好,无裂纹、孔隙等明显缺陷;复合涂层的表面硬度为324.2 HV0.2,是7075铝合金基体的2.28倍,涂层的硬度分布沿熔池深度方向逐渐递减,呈梯度分布;复合涂层中的增强体是由Al0.983Cr0.017、Al86Cr14、AlCr2、和Cr等混合组成,受熔池温度、熔液黏度等影响,增强体含量沿熔池深度方向逐渐减少,也呈梯度分布;Al、Cr之间的反应机理为液-固反应、固-固反应2种;复合涂层的强化机制主要是增强体承载、界面传载和位错强化。     

A mechanical model for the quantification of the effect of laser quenching on CTOD in steels

The technology of laser quenching is widely used to improve the surface properties of steels in surface engineering. Generally, laser quenching of steels can lead to two important results. One is the generation of residual stress in the surface layer. In general, the residual stress varies from the surface to the interior along the quenched track depth direction, and the residual stress variation is termed as residual stress gradient effect in this work. The other is the change of mechanical properties of the surface layer, such as the increases of the micro-hardness, resulting from the changes of the microstructure of the surface layer. In this work, a mechanical model of a laser-quenched specimen with a crack in the middle of the quenched layer is developed to quantify the effect of residual stress gradient and the average micro-hardness over the crack length on crack tip opening displacement (CTOD). It is assumed that the crack in the middle of the quenched layer is created after laser quenching, and the crack can be a pre-crack or a defect due to some reasons, such as a void, cavity or a micro-crack. Based on the elastic–plastic fracture mechanics theory and using the relationship between the micro-hardness and yield strength, a concise analytical solution, which can be used to quantify the effect of residual stress gradient and the average micro-hardness over the crack length resulting from laser quenching on CTOD, is obtained. The concise analytical solution obtained in this work, cannot only be used as a means to predict the crack driving force in terms of the CTOD, but also serve as a baseline for further experimental investigation of the effect after laser-quenching treatment on fracture toughness in terms of the critical CTOD of a specimen, accounting for the laser-quenching effect. A numerical example presented in this work shows that the CTOD of the quenched can be significantly decreased in comparison with that of the unquenched.     

玄武岩颗粒增强7A04铝基复合材料的界面结构及力学行为

采用喷射成形技术制备7A04铝合金及玄武岩颗粒增强7A04铝合金复合材料,利用金相显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)和能谱(EDS)分析复合材料微观组织和界面结构,对比研究复合材料的力学性能。结果表明:玄武岩颗粒在铝基体中弥散分布,并与铝基体形成强力结合界面,玄武岩颗粒边缘的SiO2不断被反应生成的Al2O3取代,形成一层几十纳米厚度的高温反应层,反应生成的Al2O3强化玄武岩颗粒与铝基体的结合界面;弥散分布的玄武岩颗粒促进基体中位错增殖、空位形成和析出相的析出,析出相主要以板状的η(MgZn2)相和亮白色条状或椭球状的T(Al2Mg3Zn3)相为主,结合界面、高位错密度及弥散分布的第二相显著提高复合材料的力学性能,添加玄武岩颗粒的7A04铝合金复合材料的屈服强度和极限拉伸强度分别达667 MPa和696 MPa,与未添加玄武岩颗粒的7A04铝合金相比分别提高10.4%和10.1%。     

Prediction of inhomogeneous texture in clad sheet metals by hot roll bond method

A finite element analysis was applied to analyze the evolution of an inhomogeneity of rolling texture in hot rolled clad metal with Taylor-Bishop-Hill model and Renourd-Winterberger method. The shear texture has been developed in the surface layer of the aluminum and plane strain texture has been developed in the center layer. The calculated texture variations through thickness direction could simulate experimental texture using deformation gradient from FEM. The ratio of shear strain to rolling strain, x, which represents the degree of rotation about transverse direction could give the degree of development of shear texture. The larger value of x gives the larger crystal rotation about transverse direction and subsequently the development of shear texture. The calculated (111) pole figures were in good agreement with experimentally measured pole figures.     

Resistivity Distribution of Multicrystalline Silicon Ingot Grown by Directional Solidification

The effects of impurities on the resistivity distribution and polarity of multicrystalline silicon ingot prepared by directional solidification were investigated in this article. The shape of the equivalence line of the resistivity in the vertical and cross sections was determined by the solid-liquid interface. Along the solidification height of silicon ingot, the conductive type changed from p-type in the lower part of the silicon ingot to n-type in the upper part of the silicon ingot. The resistivity in the vertical section of the silicon ingot initially increased along the height of the solidified part, and reached its maximum at the polarity transition position, then decreased rapidly along the height of solidified part and approached zero on the top of the ingot because of the accumulation of impurities. The variation of resistivity in the vertical section of the ingot has been proven to be deeply relevant to the distribution of Al, B, and P in the growth direction of solidification.     

Variety of solidification structures in Al-2.89%Fe alloy solidified under high magnetic field

考察了冷却速率、磁场强度及高梯度磁场对Al-2.89%Fe(质量分数)过共晶合金中Al3Fe 相形貌及分布规律的影响. 结果表明, 在无磁场条件下, 初生Al3Fe相沉积在试样下部; 施加12 T强磁场后, 初生Al3Fe相所受磁力作用和重力作用相平衡, 在整个试样中均匀分布, 且沿着易磁化方向[121]发生定向排列, 其取向程度不受冷却速率的影响, 但随着磁场强度的增大而加强; 在高梯度磁场中, 初生Al3Fe相所受磁力作用大于重力作用而偏聚在试样的上部, 且多个针状初生Al3Fe相结合在一起, 形成近似星状聚合体. 此外, 对强磁场的作用机理进行了分析和探讨.     

Cu／Al真空扩散焊接显微组织分析

采用真空扩散焊工艺方法,对Cu与Al扩散焊接头的组织性能进行了试验,利用扫描电镜（SEM）、电子探针9EPMA）、显微硬度等测试焊接过渡区及基体组织和性能进行了分析。试验结果表明：采用真空扩散焊工艺,在加热温度530－540℃,保温时间60min,压力11．5MPa时,在Cu/Al界面处形成明显的扩散过渡区,扩散区域宽约40μm。在铜侧过渡区中产生金属间化合物,会出现显微硬度高峰区,控制Al的扩散浓度可避免或减少界面处金属间化合物的产生。