Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with SiC particles was produced using an accumulative roll bonding (ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements (Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.     

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.     

复合轧制工艺对Al/Mg复合板冶金结合层组织和性能的影响

采用AZ31镁合金和纯铝进行高温复合轧制制备镁-铝复合板,使其兼具铝的表面耐蚀性和镁合金的高比强度特性.采用金相显微镜、扫描电子显微镜和电子万能拉伸机等设备,研究了不同热轧温度及退火工艺参数对铝-镁复合界面的显微组织和结合强度的影响.结果表明：300 ℃轧制,镁-铝复合板出现严重边裂;450 ℃轧制,边裂消失;在轧制温度为400 ℃、压下率为50%、300 ℃退火2 h的条件下得到的复合板界面结合强度最大,为7.5 MPa.     

Cu-(B4C)p metal matrix composites processed by accumulative roll-bonding

In this study, Cu/B4C metal matrix composites were prepared by accumulative roll-bonding (ARB). The microstructure of the processed samples was characterized by TEM, SEM and optical microscopy. The microhardness, uniaxial tensile and four-point probe tests were carried out to evaluate the mechanical properties and electrical resistivity of the ARBed monolithic and composite samples. The results showed that the reinforcement distribution was improved by increasing ARB cycles, which was quantitatively confirmed by some models. Based on TEM observations, the formation of an ultrafine grained structure in the composite matrix was also approved. It was shown that with increasing ARB cycles, the microhardness and tensile strength of the monolithic Cu samples were enhanced up to the 3rd cycle and then saturated, but the microhardness and tensile strength of the composites showed an increasing trend to the last cycle. Apart from a substantial improvement in the mechanical properties of the Cu/B4C composites, a minor decrement in electrical conductivity was detected after six ARB cycles.     

超声波搅拌时间对原位自生Mg2Si/Al基复合材料凝固组织和力学性能的影响

为了研究铝基复合材料的凝固组织和力学性能,采用超声波搅拌的方法制备了原位自生Mg₂Si/Al基复合材料.利用X射线衍射仪(XRD)、金相显微镜(OM)和扫描电子显微镜(SEM)分析其微观形貌,并通过硬度检测和拉伸试验测试其力学性能.结果表明:超声波搅拌不但能够细化初生Mg₂Si颗粒,改变凝固组织形貌,而且具有除气除杂功能,二者共同提高了Mg₂Si/Al基复合材料的力学性能;经过超声波搅拌的Mg₂Si/Al基复合材料与未经过超声波搅拌的Mg₂Si/Al基复合材料相比,抗拉强度与伸长率总体呈上升趋势,其断口形貌均为准解理面.在超声时间为40 s时,抗拉强度和伸长率达到最大值,分别为201 MPa和5.63%,相比未超声处理的Mg₂Si/Al基复合材料的抗拉强度和伸长率,分别增长了139.29%和178.71%;复合材料的硬度先升高后降低,超声作用时间为30 s时硬度最佳,为116.96(HB).     

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.     

Mg/Al异种材料瞬间液相过冷连接工艺研究

采用瞬间液相过冷连接工艺对AZ31镁合金和5083铝合金进行连接实验,研究保温扩散时间t2对焊缝微观组织及力学性能的影响。利用SEM,EDS,XRD和微观硬度计对接头剖面的微观组织和力学性能进行表征;在拉伸试验机上测试接头拉伸强度,利用SEM对断口形貌进行分析。研究结果表明:采用瞬间液相过冷连接工艺可以实现Mg/Al异种材料的有效连接;随着保温扩散时间t2的增加,接头的抗拉强度随之提高,当t2=30 min时,接头抗拉强度最高达到20.5 MPa;拉伸断口形貌具有明显的脆性断裂的特征,铝合金侧主要有解理面和撕裂棱组成,而镁合金侧属于典型的沿晶断裂形貌;在接头处形成MgAl,Mg2Al3,Mg0.44Al0.56和Mg17Al12金属间化合物,结合界面的微观维氏硬度最高达320。     

铜/铝异步轧制复合带的界面反应与强化机制

采用同步和异步轧制复合工艺制备铜/铝复合带,研究退火过程中的界面反应和异步轧制工艺的强化机制.利用扫描电镜观察界面微观组织和拉伸断口形貌,通过线扫描和电子探针分析界面元素分布,采用XRD进行界面物相分析,通过剥离和拉伸实验研究复合带的力学性能.结果表明,经400℃保温1h后界面形成具有三个亚层的扩散层组织,各亚层内元素含量存在突变;铝剥离表面检测到大量铜元素,化合物相包括CuAl₂,Cu₉Al₄,CuAl和Cu₄Al,而铜剥离表面只检测到Cu₉Al₄和Cu₄Al;异步轧制工艺可以提高界面结合强度和复合带的拉伸性能,使界面层在拉伸断裂后破坏程度降低.     

Processing and characterization of the microstructure and mechanical properties of Al6061–TiB2 composite

In the present research, aluminum metal matrix composites were processed by the stir casting technique. The effects of TiB2 rein-forcement particles, severe plastic deformation through accumulative roll bonding (ARB), and aging treatment on the microstructural charac-teristics and mechanical properties were also evaluated. Uniaxial tensile tests and microhardness measurements were conducted, and the micro-structural characteristics were investigated. Notably, the important problems associated with cast samples, including nonuniformity of the rein-forcement particles and high porosity content, were solved through the ARB process. At the initial stage, particle-free zones, as well as particle clusters, were observed on the microstructure of the composite. However, after the ARB process, fracturing phenomena occurred in brittle ceramic particles, followed by breaking down of the fragments into fine particles as the number of rolling cycles increased. Subsequently, com-posites with a uniform distribution of particles were produced. Moreover, the tensile strength and microhardness of the ARB-processed com-posites increased with the increase in the reinforcement mass fraction. However, their ductility exhibited a different trend. With post-deforma-tion aging treatment (T6), the mechanical properties of composites were improved because of the formation of fine Mg2Si precipitates.     

TiB2含量对原位自生TiB2/2219铝基复合材料组织与性能的影响

利用混合盐高温反应法制备了原位自生TiB2/2219铝基复合材料铸锭. 通过光学显微镜、扫描电镜、X射线等显微组织表征方法以及弹性模量、室温拉伸和室温摆锤冲击实验等测试手段,研究了TiB2含量对原位自生TiB2/2219铝基复合材料组织和性能的影响. 研究表明,当TiB2质量分数由0提高到5%时,TiB2颗粒尺寸和TiB2/2219铝基复合材料铸锭的平均晶粒尺寸逐渐减小,固溶时效态的TiB2/2219铝基复合材料板材的弹性模量和强度显著上升,但延伸率和冲击韧性下降. 当质量分数为5%时,TiB2/2219铝基复合材料板材的弹性模量、抗拉强度、屈服强度和延伸率分别达到88.7 GPa、（474.2±2） MPa、（400.6±1） MPa和（4.7±0.1）%.     

Characteristic investigation of trilayered Cu/Al8011/Al1060 composite: Interface morphology,microstructure, and in-situ tensile deformation

In this work, Cu/Al8011/Al1060 trilayered composite with an ultrathin copper layer was fabricated successfully by the hybrid process of cast-rolling and hot-roll-bonding. The effects of heat treatment were investigated on the microstructure and mechanical behavior of the composite. The results showed that annealing temperatures above 300 ​°C led to the formation of new intermetallic compounds that joined their initial counterparts. Also, the interface growth was fast above 340 ​°C. It was found that the annealing temperature of 320 ​°C led to the optimal tensile properties of the composite. Through rolling, hard-brittle IMCs imposed intense plastic strains on the surrounding regions, resulting in further grain refinement of both metals in the vicinity of the interface. Although the kernel average misorientation of the trilayered composite was almost identical with the Cu/Al8011 bimetal, its amount was considerably decreased after heat treatment, as the distorted structure changed into a nearly strain-free one using the restoration phenomenon. The SEM-based in-situ tensile test showed that crack initiation occurred within the IMCs and propagated into the Cu strip, leading to its early fracture. However, the strength-displacement curve during in-situ tensile deformation did not decrease significantly due to the ultrathin copper layer.     

5052/6005A异种铝合金激光填丝焊接头组织与力学性能研究

对铝合金6005A与5052进行异种铝合金激光填丝焊,研究了焊接接头的微观组织及力学性能,并对接头断口微观特征进行了分析。结果表明,焊缝中心为等轴晶与树枝晶,铝合金6005A侧熔合线附近存在清晰柱状晶,铝合金5052侧熔合线较为模糊。拉伸时在铝合金6005A侧热影响区断裂。焊接件焊接接头的平均抗拉强度为197.9 MPa,达到铝合金6005A母材抗拉强度的83%。断裂特征为韧性断裂,接头弯曲性能良好。     

纳米碳管铝基复合材料组织与性能的研究

试验采用搅拌铸造法制备了纳米碳管增强铝基复合材料,对其显微组织、硬度、抗拉强度和电阻率进行了研究.结果表明：纳米碳管的加入能够细化复合材料晶粒,表面镀铜后可以抑制基体与增强体之间的界面反应,避免脆性碳化物的生成;复合材料的硬度和抗拉强度随着纳米碳管加入量的增加先增加后减小,纳米碳管的质量分数为1.0%时,达到最大值,与基体相比分别增加了34.8%和34.4%;纳米碳管的加入对基体的导电性影响不大.     

Influence of ECAP on the fatigue behavior of age-hardenable 2xxx aluminum alloy

The fatigue behavior under load control and the mechanical properties of commercial 2011 aluminum as an age-hardenable Al alloy was studied. To estimate the effects of the equal channel angular pressing (ECAP) process, solution heat treatments, and aging on the fatigue life, tests were conducted at four different stages:furnace cooling; furnace cooling plus one ECAP pass; solid solution heat treatment, quenching, one ECAP pass plus aging at peak age level; and the T6 condition. Only one pass was possible at room temperature because of the high strength of the material. The fracture surface morphology and microstructure after fatigue were evaluated by scanning electron microscopy (SEM). The experimental results revealed that the optimum fatigue life under load control, the tensile strength, and the Vickers hardness of the material were interdependent. The optimum fatigue life under load control was achieved by increasing the tensile strength and hardness of the material.     

表面处理方式对钛/钢复合板界面结合性能的影响

采用真空制坯轧制复合法,在相同的加热温度、轧制道次和压下量等工艺条件下,分别对钢丝刷打磨、酸洗和带水砂带机打磨的表面处理方式,研究了3组钛/钢复合板的界面组织和力学性能.分析了表面处理方式对界面结合性能的影响.结果表明:带水砂带机表面处理方式下的钛/钢复合界面生成连续均匀的TiC层,剪切断口呈韧窝状,界面剪切强度稳定,平均强度达到242.6MPa.其他两种表面处理方式下的钛/钢复合板界面生成断续的TiC层,其剪切强度均未满足国家标准.     

On the liquid-phase technology of carbon fiber/aluminum matrix composites

The main problems with the liquid-phase technology of carbon fiber/aluminum matrix composites include poor wetting of the fiber with liquid aluminum and formation of aluminum carbide on the fibers' surface. This paper aims to solve these problems. The theoretical and experimental dependence of porosity on the applied pressure were determined. The possibility of obtaining a carbon fiber/aluminum matrix composite wire with a strength value of about 1500 MPa was shown. The correlation among the strength of the carbon fiber reinforced aluminum matrix composite, the fracture surface, and the degradation of the carbon fiber surface was discussed.     

采用超声组装与滚压工艺制备铝–碳纳米管复合材料

This study introduced a novel fabrication of aluminum–carbon nanotube (CNT) composites by employing bulk acoustic waves and accumulative roll bonding (ARB). In this method, CNT particles were aligned using ultrasonic standing wave in an aqueous media, and the arrayed particles were precipitated on the aluminum plate substrate. Then, the plates rolled on each other through the ARB process with four passes. Optical and scanning electron micrographs demonstrated the effective aligning of CNTs on the aluminum substrate with a negligible deviation of arrayed CNTs through the ARB process. The X-ray diffraction pattern of the developed composites showed no peaks for carbon and aluminum carbide. In addition, tensile tests showed that the longitudinal strength of the specimens processed with aligned CNTs was significantly greater than that of the specimens with common randomly dispersed particles. The proposed technique is beneficial for the fabrication of Al–CNT composites with directional mechanical strength.     

AlSi/AlMn双金属复合材料制备试验研究

在自行设计和制造的双金属复合材料连铸设备上,通过工艺参数的合理配置,成功制备出尺寸为150mm×120mm×100mm的AlSi/AlMn双金属复合材料铸坯。分析了复合铸锭的宏观和显微组织、界面附近的元素成分以及界面结合强度和硬度分布。结果表明,复合界面为冶金结合,所制备复合材料的微观组织与化学成分分布及硬度之间有良好的对应关系。     

高挤压比下挤压工艺对AZ31B镁合金组织与力学性能的影响

研究了高挤压比条件下挤压温度、速度对AZ31B镁合金微观组织、力学性能的影响。采用光学显微镜观察了显微组织,拉伸试验测试了力学性能,并配合扫描电镜观察了拉伸试样的断口形貌。结果表明,高挤压比条件下,动态再结晶较为充分,少量晶粒长大,混晶组织消失。低温、高速挤压有助于晶粒细化,并使晶粒尺寸分布均匀,因而可获得高的抗拉强度、屈服强度以及良好的塑性。350 ℃,2 m/min条件下挤压,试样抗拉强度与延伸率最高,为336.5 MPa与 23%。低温、高速下的挤压试样的拉伸断口韧窝较深且细密,呈现明显的韧性断裂特征,而高温、低速的断口为混合断裂。     

焊接热输入对镁合金与镀铜钢冷金属过渡焊接接头性能和缺陷影响

利用冷金属过渡焊(CMT)对镁合金和镀铜钢异种金属进行焊接,填充材料选择AZ31镁合金焊丝,对焊接接头的显微组织进行检测,分析焊接接头的性能和缺陷。实验结果表明:Cu元素对镁合金在钢表面的润湿铺展起到良好的促进作用,焊接热输入影响Cu元素对镁/钢表面的润湿铺展效果。焊接接头产生富铜区,易产生裂纹,降低了焊接接头强度。经过拉伸测试,在焊接热输入为212. 2 J/mm时,焊接接头强度达到最大值3. 99 k N,但在焊接热输入达到254. 6 J/mm时,焊接强度反而降低,这是由于钎焊区生成了大量的中间层脆性化合物。焊接接头组织中检测到气孔、夹渣和裂纹等焊接缺陷的存在,这与母材表面的氧化膜和焊缝内应力有关。