Microstructure and mechanical properties of Al/Cu/Mg laminated composite sheets produced by the ARB proces

In the present study, an Al/Cu/Mg multi-layered composite was produced by accumulative roll bonding (ARB) through seven passes, and its microstructure and mechanical properties were evaluated. The microstructure investigations show that plastic instability occurred in both the copper and magnesium reinforcements in the primary sandwich. In addition, a composite with a perfectly uniform distribution of copper and magnesium reinforcing layers was produced during the last pass. By increasing the number of ARB cycles, the microhardness of the layers including aluminum, copper, and magnesium was significantly increased. The ultimate tensile strength of the sandwich was enhanced continually and reached a maximum value of 355.5 MPa. This strength value was about 3.2, 2, and 2.1 times higher than the initial strength values for the aluminum, copper, and magnesium sheets, respectively. Investigation of tensile fracture surfaces during the ARB process indicated that the fracture mechanism changed to shear ductile at the seventh pass.     

累积叠轧焊强化金属材料的力学性能

在多功能热轧机上对广泛应用的代表性金属材料Q235碳素钢和L2铝分别进行了累积叠轧焊实验,重点研究了变形温度、累积叠轧次数和压下量对金属材料强度、应力-应变曲线、显微硬度、塑性的影响规律,分析了规律形成的原因.结果表明:Q235碳素钢和L2铝在不加入任何强化元素的情况下完全可以达到良好的自身结合,材料的抗拉强度得到提高,金属材料的塑性分别有不同程度的下降.     

Microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting

The microstructure and elevated-temperature mechanical properties of dispersoid-strengthened Al-Mg-Si-Mn alloys produced by twin roll casting (TRC) and conventional mold casting (MC) were studied. A specific heat treatment at 430 ​°C for 6 ​h was applied, followed by rolling. Tensile tests were carried out at 300 ​°C. The results show that in the as-cast microstructures, equiaxed grains formed in the MC sample while elongated grains with substructures formed in the TRC sample. The eutectics in the TRC sample were much finer than those in the MC sample. Upon heat treatment, large numbers of α-Al(Fe, Mn)Si dispersoids precipitated, and the TRC sample had a greater number density of dispersoids than those in the MC sample. During the tensile test after rolling, the TRC samples exhibited higher strength than the MC samples, which resulted from the combination of the strengthening effect of the stronger dispersoids and the greater substructure hardening effect in the TRC sample; the TRC sample exhibited better ductility due to its finer initial eutectic than that in the MC sample, which depressed the stress concentration and delayed the occurrence of microcracks and fracture in the TRC sample.     

Microstructure and mechanical properties of automobile beam steels produced by EAF-CSP process

The microstructure, mechanical properties, and misorientation of automobile beam steels produced by EAF-CSP process were studied using optical microscopy (OM) and electron back-scattered diffraction (EBSD). It is shown that the microstructure of strips is mainly polygonal ferrite, and the average grain size is about 5-8 μm. The electron back-scattered diffraction results show that grain boundaries in ferrite are basically high-angle grain boundaries without remarkable preferred orientation. Hot strips of automobile beam steels possess a good combination of strength and plasticity because of their fine microstructures and low quantity of impurities.     

Processing of nanostructured metallic matrix composites by a modified accumulative roll bonding method with structural and mechanical considerations

Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. Al/B₄C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B₄C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.     

累积复合轧制工艺晶粒细化机制对1060工业纯铝组织和性能的影响

采用累积复合轧制(ARB)技术的两种工艺路径,研究变形后1060工业纯铝的显微组织和力学性能变化. 结果显示:路径A的晶粒细化效果比路径B明显;ARB 7道次后,采用路径A的试样的显微组织由拉长的细小纤维状晶粒组成,路径B的试样由扁平状晶粒组成;路径A和路径B的试样的平均晶粒尺寸分别为470nm和680nm;路径A的试样的抗拉强度提高程度大于路径B. 1060工业纯铝在ARB过程中的强化机制主要是细晶强化. 初步分析了ARB过程中材料的变形规律和细小晶粒的形成机制.     

Ti6Al4V和Al2A12的扩散连接界面组织及力学性能

采用热等静压(HIP)工艺连接Al2A12和Ti6Al4V两种不同的航空航天用材料.利用扫描电镜、能谱仪和X射线衍射仪观察连接过渡区的微观组织和组成的演化,并测试其主要的力学性能.结果表明:采用热等静压制备这两种材料的界面连接好;Ti/Al反应层界面处形成了不同的金属间化合物,例如,Al3Ti、TiAl2和TiAl;连接接头处硬度为163HV,界面连接处剪切强度达到了23MPa,比只添加镀层而无中间层的连接强度提高了约17.9%,但低于带有中间层的连接强度.由于过烧和孔隙的形成使得断裂方式是脆性断裂.由此可知,在热等静压成形过程中异种材料的元素发生了相互扩散,在扩散连接处形成了不同的金属间化合物,这些金属间化合物影响连接处的力学性能.     

Microstructure and mechanical properties of a hot-extruded Al-based composite reinforced with core-shell-structured Ti/Al3Ti

An Al-based composite reinforced with core-shell-structured Ti/Al3Ti was fabricated through a powder metallurgy route followed by hot extrusion and was found to exhibit promising mechanical properties. The ultimate tensile strength and elongation of the composite sintered at 620°C for 5 h and extruded at a mass ratio of 12.75:1 reached 304 MPa and 14%, respectively, and its compressive deformation reached 60%. The promising mechanical properties are due to the core-shell-structured reinforcement, which is mainly composed of Al3Ti and Ti and is bonded strongly with the Al matrix, and to the reduced crack sensitivity of Al3Ti. The refined grains after hot extrusion also contribute to the mechanical properties of this composite. The mechanical properties might be further improved through regulating the rela-tive thickness of Al-Ti intermetallics and Ti metal layers by adjusting the sintering time and the subsequent extrusion process.     

累积叠轧Al/Cu复合板界面反应层核-壳结构形成机制

采用累积叠轧(ARB)结合多次退火处理制备了Al/Cu复合板,重点研究了Al/Cu界面反应层核-壳结构形成机制. 结果表明:Al/Cu界面反应层的形成主要依赖于退火过程中铜原子在界面处的扩散,反应产物包括Al₂Cu、AlCu、Al₄Cu₉. 轧制变形致使反应层破碎并在基体中均匀分布,轧后退火处理导致新的反应层不断形成.最终经多次叠轧及退火处理,原始铜板材全部转变为椭球状具有核-壳结构的Al/Cu金属间化合物颗粒. 8道次复合板抗拉强度最高,达到176.8 MPa,是退火态1060抗拉强度的1.74倍;0道次复合板延伸率较好,主要是Al/Cu界面分层后铝层均匀塑性变形,应力缓慢释放所致.     

薄板坯连铸连轧工艺制备TRIP钢的力学性能与组织

在实验室条件下模拟薄板坯连铸连轧工艺试制了C-Si-Mn系TRIP钢.拉伸实验表明,实验钢的抗拉强度为610MPa,屈服强度为430MPa,屈强比为0.70,总延伸率为28.4%.组织观察发现,试样组织为铁素体 贝氏体 残余奥氏体的三相组织,实验钢中残余奥氏体的平均含量为5.8%.     

Cu/Ni多层膜的调制波长与力学性能的关系

为研究Cu/Ni多层膜的调制波长与力学性能的关系,采用计算机控制的单槽双脉冲控电位沉积系统,在Cu基体上沉积Cu/Ni多层膜,分别采用扫描电镜和纳米压痕技术对Cu/Ni多层膜的截面和硬度进行了测试.结果表明:电沉积方法制备的Cu/Ni多层膜具有良好的周期结构;在调制波长为37 nm时硬度达到极值;在调制波长小于37 nm时其硬度值明显下降.实验结果符合理论分析中多层膜的硬度随调制波长的变化规律,但临界调制波长大于理论计算结果.     

激光熔覆原位合成TiC的Ni／TiC复合层显微组织与性能研究

利用5kW CO2激光器和同轴送粉的方法,在Q235钢基材表面原位合成强化相为TiC的Ni／TiC复合材料层。研究了不同Ni相对含量对熔覆层的显微组织形貌和相组成的影响,并进行了耐磨性试验。结果表明,熔覆层的物相构成为Ni和TiC,熔覆层耐磨性随Ni相对含量的减少而增大。     

活塞用Cu和Ni增强型铝合金的 组织与性能

本文对比研究了一种新型活塞用B型铝合金与ZL109的组织与力学性能.研究表明,ZL109的组织由Al,Si,Al6Mn和Al5Fe Ni的相组成,B型铝合金由Al,Si,Al6Mn,Al2Cu,Al1.9Cu Mg4.1Si3.3(Q相),Al Ni Cu和更多的Al5Fe Ni组成;源于B型铝合金中的α铁相呈现鱼骨状和块状,减轻了ZL109组织中针片状β铁相对基体的割裂作用,La和Ce元素的Al Ni Cu相高温下可起到阻碍晶界滑动和阻碍基体变形的作用,并且组织中还生成了Al2Cu,Al5Fe Ni和Al1.9Cu Mg4.1Si3.3强化相;因而,B型铝合金的力学性能优于ZL109,且受活塞缸径尺寸规格的影响较小;B型铝合金的断裂类型为准解理断裂,呈现韧窝、舌状花样以及撕裂棱特征.     

Microstructure characteristics of Ni/WC composite cladding coatings

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr₇C₃/Cr₂₃C₆, CrB, and Ni+Ni₃Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.     

TiC强化Cr12MoV基复合材料的组织和性能分析

用原位合成铸造法制备了TiC弥散强化Cr1 2MoV钢基复合材料 ,对材料的制备工艺、力学性能及微观组织进行了系统的研究 .试验结果表明 ,用原位合成铸造法制备TiC颗粒增强钢基复合材料的工艺具有可行性 ,且易于实现工业化生产 .TiC颗粒在基体中分布均匀 ,形状呈块状和球状 ,分布在晶内和晶界上 .颗粒与基体结合良好 ,且无团聚现象 .引入TiC后材料的室温和高温强度比基体材料的强度均有提高 ,说明TiC颗粒起了良好的强化效果 .金属基体与高耐磨性的增强粒子相结合 ,使复合材料获得了优异的耐磨性能 .在提高材料的强度、耐磨性、抗热疲劳性能的同时 ,TiC的加入也使材料的塑性和韧性有一定程度的下降     

Microstructure and mechanical properties of a novel Zr-based bulk metallic glass composite

Zr48.5Cu46.5Al5 bulk metallic glass （BMG） composites with diameters of 3 and 4 mm were prepared through suction casting in an arc melting furnace by modulating the alloy composition around the monothetic BMG composition of the high glass forming ability. Microstructural characterization reveals that the composites contain micron-sized CuZr phase with martensite structure, as well as nano-sized Zr2Cu crystalline particles and Cu10Zr7 plate-like phase embedded in an amorphous matrix. Room temperature compression tests showed that the composites exhibited significant strain hardening and obvious plastic strain of 7.7% for 3 mm and 6.4% for 4 mm diameter samples, respectively.     

铝合金表面机械球磨Ni-Al-Mo复合涂层的制备及其摩擦特性研究

通过机械球磨方法在铝合金表面制备了Ni-Al-Mo复合涂层,对涂层微观组织、组成成分和摩擦学性能等进行了分析.结果表明:经过7 h机械球磨制备的Ni-Al-Mo复合涂层内元素均匀分布;550℃退火后涂层中均有Al3 Ni金属间化合物新相生成;复合涂层中Al3 Ni和Mo的存在使得涂层硬度高于铝合金基体和Ni-Al涂层,...     

热型连铸Al-Cu合金的组织与性能

在热型连铸设备上制取了 Al- 1 0 %Cu合金的线材 ,对线材的组织与室温拉伸性能进行了实验分析 ,发现该工艺可显著提高材料的轴向性能 ,认为这是硬脆的α-Al+ Cu Al2 共晶体在材料中沿轴向分布的结果 .     

外氧化法制备Al_2O_3/Cu复合材料的组织与性能

在不添加外氧化剂Cu2O的条件下,通过外氧化法生成氧化剂Cu2O,真空条件下进行Al2O3内氧化与烧结、热挤压和冷拉拔制备了Al2O3颗粒弥散强化的铜基复合材料,对其微观组织和硬度、导电率进行了分析测试。结果表明:外氧化法制备的Al2O3/Cu复合材料,随着Al2O3含量的增加,材料的硬度增加,而导电率减小;进行热挤压变形后,Al2O3/Cu复合材料的硬度随变形量的增加而增加,而导电率降低;制备的冷拉拔变形率为24.8%的1.04wt.%Al2O3/Cu复合材料硬度为69.2 HRB,导电率为73.6%IACS。     

原位观察铜网格增强Al/Cu复合材料的断裂行为

将一种按正交法编织的铜网格作为增强体引入到铝基体中制备了Al/Cu复合材料,再借助原位拉伸扫描电镜(SEM),观察了铝铜复合材料的组织演变,研究了其断裂机理与力学性能之间的关系.结果表明:在相同轧制变形量下,25 ℃冷轧和400 ℃热轧均可破碎增强体铜网格,并使其均匀分布于基体铝板.复合板原位拉伸下的载荷-位移曲线均表现出明显的弹性阶段、塑性阶段和失效阶段,微裂纹在Cu颗粒周围和应力集中处萌生,主裂纹及其扩展主要是Cu颗粒周围界面分层开裂与微裂纹沿滑移线方向的扩展共同作用下形成的,并且最终沿滑移线的断裂路径与单轴拉伸方向呈45°.发生在Al层的塑性断裂和Al/Cu结合界面上的界面分层断裂是Al/Cu复合板两种主要的失效方式.