Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Effect of HEA/Al composite interlayer on microstructure and mechanical property of Ti/Mg bimetal composite by solid-liquid compound casting

In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can effectively inhibit the interfacial diffusion between Al and Mg,which is conducive to the formation of solid solution,especially when the thickness of HEA is 800 nm.With the increase of casting temperature from 720 ℃ to 730 ℃,740℃,and 750 ℃,α-Al(Mg),α-Al(Mg)+Al3Mg2,Al3Mg2+Al12Mg17,and Al12Mg17+δ-Mg are formed at the interface of Ti/Mg bimetal,respectively.When the thickness of the HEA layer is 800 nm and the pouring temperature is 720 ℃,the bonding strength of the Ti/Mg bimetal can reach the maximum of 93.6 MPa.

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.

选区激光熔化成形TiB_(2)/Al-Si-Mg大尺寸复杂构件

选区激光熔化(SLM)成形大尺寸复杂构件厚度多样、成形高度较高、方向复杂,需要研究构件微观组织均匀性和力学性能稳定性。本文以SLM成形TiB_(2)/Al-Si-Mg复合材料为研究对象,分析复合材料多级微观组织,对比不同成形厚度、高度、方向下复合材料的力学性能。结果表明:复合材料表现出熔池特征结构,细小等轴晶粒组织均匀分布且随机取向,纳米TiB_(2)颗粒在材料内部弥散分布。随成形厚度增加,复合材料伸长率保持稳定,抗拉强度受本征热处理影响略微增大;在不同成形高度下,复合材料抗拉强度和伸长率保持稳定;在不同成形方向下,复合材料抗拉强度保持稳定,伸长率受熔池结构影响在水平方向略高。基于以上结果,成功制备大飞机舱门铰链臂(588 mm×318 mm×470 mm)复杂结构件。

超声施振方式对消失模铸造Al/Mg双金属复合材料界面组织和力学性能的影响

研究了连续超声振动和间歇超声振动两种施振方式对消失模铸造Al/Mg双金属材料界面组织和力学性能的影响。结果表明,未施加超声振动Al/Mg双金属界面由Al-Mg金属间化合物区和共晶组织区组成,两个区域边界存在一层氧化膜,阻碍了元素扩散,Mg_(2)Si相呈网状,团聚分布于金属间化合物区。两种超声施振方式均能通过超声空化效应和声流效应破碎和消除氧化膜,并使Mg_(2)Si相细化和分散于整个界面,部分共晶组织转变为金属间化合物,提高了界面组织和显微硬度分布均匀性。连续超声振动作用下Al/Mg双金属界面剪切强度达到53.9 MPa,相比未超声处理提升63.8%。间歇超声振动作用下,界面厚度较连续超声振动减小,然而局部区域存在孔洞缺陷和Mg_(2)Si相局部聚集,削弱了对界面的强化效果,但界面剪切强度仍达到49.5 MPa。

不同铝合金对Al/Mg/Al层状复合材料腐蚀行为的影响

将镁合金与铝合金经过热轧制成Al/Mg/Al层状复合材料,结合析氢试验、电化学试验和电偶试验,对1060/AZ31/1060、5052/AZ31/5052和6061/AZ31/6061在3.5%(质量分数)NaCl溶液中腐蚀行为进行研究,通过分析其腐蚀形貌、腐蚀产物、析氢速率、动电位极化曲线和交流阻抗谱,探究Al/Mg/Al层状复合材料的腐蚀机理。结果表明:Al/Mg/Al层状复合材料的表面腐蚀行为与铝合金的腐蚀行为相似,其相对于原始镁合金的腐蚀电流密度降低了两个数量级;Al/Mg/Al层状复合材料截面腐蚀产物呈颗粒状密集分布在镁一侧,腐蚀行为主要受电偶效应的影响,镁-铝电偶对电偶电流可达10^(-3)A·cm^(-2)数量级;对应的三种镁-铝电偶对电偶电流密度和电偶电位与混合电位理论拟合值相差不大;三种Al/Mg/Al层状复合材料中5052/AZ31/5052的整体耐蚀性最好。

铸造Mg/Al复合材料工艺参数和复合界面的研究进展

Mg/Al复合材料在汽车、航空航天和电子设备等领域广泛应用。相对于制备复合板的轧制工艺,铸造能够用于制备复杂的复合材料构件,并具有成本低和生产效率高等优点。然而,铸造Mg/Al复合材料存在微观组织难以控制和界面结合强度较低等问题,限制了材料性能。影响复合材料性能的因素包括铸造工艺、界面处理和扩散层组织等。目前,主要通过控制晶粒尺寸、界面强化和界面反应等方式来强化复合材料。本文综述了铸造法制备Mg/Al复合材料过程中的工艺参数对复合界面的影响,包括扩散层厚度、晶粒尺寸等,最后对此方向提出自己的见解。

衬板叠轧Mg/Al复合板基体组织演变优化强塑性机制

Mg/Al复合板兼并了镁合金的轻质性及铝合金的可塑性、耐腐蚀等性能,显著增强了其综合性能,但制造周期长、工艺要求高等不足制约了异质复合板成形技术的快速发展。为此,本文提出一种衬板辅助叠轧成形新方法。研究结果表明:3ARB时Mg/Al复合板抗拉强度可达235 MPa,伸长率为14.7%,镁板中出现明显的韧窝,呈韧性断裂特征,综合性能为最佳。由于此时Mg板基面滑移与非基面滑移同时开动,促进了动态再结晶的生成,此时Mg板再结晶比例为77.21%。随着累积叠轧的进行,大角度晶界增加和晶粒细化明显,原始晶粒已经基本破碎细化成等轴晶,Mg、Al基体硬度波动逐渐减小,复合板内部结构逐渐趋于稳定。本研究可为高性能异质复合板成形制造提供了一种新思路。

Microstructure and dry sliding wear behavior of cast Al-Mg_2Si in-situ metal matrix composite modified by Nd

The microstructure and dry sliding wear behav- ior of cast Al-18 wt% MgaSi in-situ metal matrix com- posite modified by Nd were investigated. Experimental results show that, after introducing a proper amount of Nd, both primary and eutectic Mg2Si in the Al-18 wt% Mg2Si composite are well modified. The morphology of primary Mg2Si is changed from irregular or dendritic to polyhedral shape, and its average particle size is signifi- cantly decreased. Moreover, the morphology of the eutectic MgzSi phase is altered from flake-like to very short fibrous or dot-like. The wear rates and friction coefficient of the composites with Nd are lower than those without Nd. Furthermore, the addition of 0.5 wt% Nd changes the wear mechanism of the composite from the combination of abrasive, adhesive, and delamination wear without Nd into a single mild abrasion wear with 0.5 wt% Nd.

Comparison of microstructures and mechanical properties of composite extruded AZ31 sheets

The microstructures and mechanical properties of the composite extruded AZ31/AZ31 and AZ31/4047 Al sheets were investigated and made a comparison to the conventional extruded AZ31 sheet.Owing to the introduced intense shear deformation at the interface during the composite extrusion,grain refinement and tilted texture were detected in AZ31 layers of the AZ31/AZ31 and AZ31/4047 Al sheets,while the conventional extruded AZ31 sheet exhibited a relative coarse,inhomogeneous microstructure and strong basal texture.The compressiontension yield ratio was increased gradually from the AZ31 to the AZ31/AZ31 and AZ31/4047 Al sheets.Besides,the AZ31/4047 Al sheet could successfully accomplish the whole bending forming process at room temperature,while the AZ31 and AZ31/AZ31 sheets were both bend-formed to failure with significant cracks in the outer tensile region under the identical bending parameters.Moreover,under the same bending strain,both the outward offset degree of strain neutral layer and the sheet thickening were more serious in the AZ31/4047 Al composite sheet than those of the AZ31 and AZ31/AZ31 sheets.The foremost reason was the quite wide gap of material properties between Mg alloy AZ31 layer(tensile loading in the outer region)and Al 4047 layer(compressive loading in the inner region).

Preparation, structure and properties of Mg/Al laminated metal composites fabricated by roll-bonding, a review

Laminated metal composites(LMCs) are a unique composite material and have great application prospects in automobiles, ships, aircraft,and other manufacturing industries. As lightweight materials, the Mg/Al LMCs are expected to combine the advantages of both Mg and Al alloys to broaden their application prospects. Roll-bonding is the most popular process for the fabrication of Mg/Al LMCs due to high production efficiency and good product quality stability. The roll-bonding process involves the deformation of the substrates and the formation of the interfacial diffusion layer. The latter will directly determine the interface bonding strength of Mg/Al LMCs. Bonding strength is very sensitive to the thickness of the reaction layer in the diffusion layer. When the thickness of the reaction layer exceeds 5 μm, the bonding strength decreases sharply. Therefore, controlling the thickness of the reaction layer is very important for the design of rolling parameters.The latest research also showed that the addition of intermediate layer metal and the construction of three-dimensional interfaces can further improve the interface bonding strength. How to apply these methods to roll-bonding is the focus of future research. Recently, a new rolling technique, corrugated roll/plat roll rolling+flat roll/flat roll rolling has been developed to fabricate Mg/Al LMCs. It can effectively promote the deformation of the hard layer and generate a wavy interface, resulting in the enhancement of the bonding quality and rolling quality.In the current review, the effects of rolling parameters and subsequent annealing on the interface structure of Mg/Al LMCs were elaborated in detail. The application of some special rolling techniques in the preparation of Mg/Al LMCs was also summarized. The latest research results on the relationship between interface structure and mechanical properties of Mg/Al LMCs were reviewed. Finally, further research directions in this field were proposed.

Effect of SiC particle addition on microstructure of Mg_2Si/Al composite

In the present study, by adding SiC particles into Al-Si-Mg melt, Mg2Si and SiC particles hybrid reinforced Al matrix composites were fabricated through the Mg2Si in situ synthesis in melt combined with the SiC ex situ stir casting. The as-cast microstructure containing primary Mg2Si and SiC particles that distribute homogenously in Al matrix was successfully achieved. The effects of SiC particle addition on the microstructure of Mg2Si/Al composites were investigated by using scanning electron microscopy(SEM) and XRD. The results show that, with increasing the fraction of the SiC particles from 5wt.% to 10wt.%, the morphologies of the primary Mg2Si particulates in the prepared samples remain polygonal, but the size of the primary phase decreases slightly. However, when the SiC particle addition reaches 15wt.%, the morphologies of the primary Mg2Si particulates change partially from polygonal to quadrangular with a decrease in size from 50 μm to 30 μm. The size of primary Al dendrites decreases with increasing fraction of the SiC particles from 0wt.% to 15wt.%. The morphology of the eutectic Mg2Si phase changes from a fi ber-form to a short fi ber-form and/or a dot-like shape with increasing fraction of the SiC particles. Furthermore, no signifi cant change in dendrite arm spacing(DAS) was observed in the presence of SiC particles.

Effects of Mg content on microstructure and mechanical properties of SiC_p/Al-Mg composites fabricated by semi-solid stirring technique

10%(volume fraction) SiCp/Al-Mg composites with different Mg contents were successfully fabricated by semi-solid mechanical stirring technique under optimum processing conditions.Effects of Mg content on microstructure and mechanical properties were studied by scanning electron microscopy(SEM),X-ray diffractometry(XRD) and transmission electron microscopy(TEM).The results indicate that SiC particles disperse homogeneously in Al-Mg matrix and interfacial reaction between Al matrix and SiC particles is effectively controlled.Distribution of SiCp reinforcement and interfacial bonding are improved by adding Mg.Additionally,the mechanical properties of composites are remarkably improved with the Mg content increasing.

Study on in-situ Mg_2Si/Al-Si composites with different compositions

Effects of chemical composition and heat treatment on microstructures and mechanical properties of in-situ Mg2Si/Al-Si composites were investigated.It was found that,in the microstructure of an Al-5.7wt% Mg2Si composite with 8.2wt% extra Si,the binary eutectic Mg2Si locates at the grain boundaries with an undeveloped Chinese script-like morphology,and the primary α-Al is formed into a cell structure due to the selective modif ication effect of the modif iers of mischmetal and Strontium salt;whereas in the composite with a near Al-Mg2Si eutectic composition and little extra Si content,the intercrescence eutectic Mg2Si formed with the binary eutectic α-Al grows into integrated Chinese script-like shape.As Si content increases,the eutectic Mg2Si dendrite becomes coarser in morphology but less in volume fraction.Hardness and tensile strength of the cast Mg2Si/Al-Si composites do not increase with increasing of Mg content,but they are related to the size and morphology of the eutectic and primary Mg2Si phases.Heat treatment with optimal parameters is an effective way to improve the properties of the in-situ composites.

Centrifugal casting processes of manufacturing in situ functionally gradient composite materials of Al-19Si-5Mg alloy

Cylindrical components of in situ functionally gradient composite materials of Al-19Si-5Mg alloy were manufactured by centrifugal casting. Microstructure characteristics of the manufactured components were observed and the effects of the used process factors on these characteristics were analyzed. The results of observations shows that, in thickness, the components possess microstructures accumulating lots of Mg2Si particles and a portion of primary silicon particles in the inner layer, a little MgzSi and primary silicon particles in the outer layer, and without any Mg2Si and primary silicon particle in the middle layer. The results of the analysis indicate that the rotation rate of centrifugal casting, mould temperature, and melt pouring temperature have evidently affected the accumulation of the second phase particles. Also, the higher the centrifugal rotation rate, mould temperature, and melt pouring temperature are, the more evident in the inner layer the degree of accumulation of Mg2Si and primary silicon particles is.

The evolution of microstructure and mechanical properties during high-speed direct-chill casting in different Al–Mg_2Si in situ composites

The effect of high-speed direct-chill(DC) casting on the microstructure and mechanical properties of Al–Mg_2Si in situ composites and AA6061 alloy was investigated. The microstructural evolution of the Al–Mg_2Si composites and AA6061 alloy was examined by optical microscopy, field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). The results revealed that an increase of the casting speed substantially refined the primary Mg_2Si particles(from 28 to 12 μm), the spacing of eutectic Mg_2Si(from 3 to 0.5 μm), and the grains of AA6061 alloy(from 102 to 22 μm). The morphology of the eutectic Mg_2Si transformed from lamellar to rod-like and fibrous with increasing casting speed. The tensile tests showed that the yield strength, tensile strength, and elongation improved at higher casting speeds because of refinement of the Mg_2Si phase and the grains in the Al–Mg_2Si composites and the AA6061 alloy. High-speed DC casting is demonstrated to be an effective method to improve the mechanical properties of Al–Mg_2Si composites and AA6061 alloy billets.

Synthesis, Characterization of Mesoporous Al-Mg Composite Oxide and Catalytic Performance for Oxyethylation of Fatty Alcohol

A mesoporous Al-Mg composite oxide with a hexagonal structure was synthesized with aluminium nitrate and magnesium nitrate as the reagents and sodium dodecyl sulfate（SDS） as the template in the presence of ethylenediamine. The XRD, nitrogen adsorption-desorption and TEM studies indicate that the composite has a hexagonal framework structure and an average pore diameter of 2. 6 nm. The TG/DTA spectra indicate that the decomposition and the removal of the occluded surfactant of the sample take place in a range of 230-550 ℃. The mesoporous Al-Mg composite oxide exhibites a highly catalytic activity for the oxyethylation of fatty alcohols. Narrow-range distributed ethoxylates are formed in the presence of the mesoporous Al-Mg composite oxide catalyst. The distribution selectivity coefficient（Cx） is 24 when the mesoporous Al-Mg composite oxide was used as a catalyst for the oxyethylation of octanol and the average adduct degree of ethoxylates is 6. 4.

Strengths and Fracture Mechanisms of Al_2O_3 Short Fiber Reinforced Al-Mg Alloy Matrix Composite at Elevated Temperatures

Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of AI2O3 short fiber reinforced AI-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally, the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideration of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300℃) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.

Effect of Mg Addition on the Structure and Properties of Al-4.5 Cu-3.4 Fe <i>In-Situ</i>Cast Composite

Ternary Al-4.5 (wt%) Cu-3.4 (wt%) Fe in-situ composite was prepared at 1100&#176;C by conventional casting method. However, this particular alloy contains larger needle-shaped intermetallics of Al3Fe phase. These exert adverse effect on the mechanical properties of the alloys. The larger shape and uneven orientation of the intermetallic were found to be responsible for the degradation of properties. The main purpose of this study was to modify the geometry of those needles by adding magnesium (Mg) as a fourth material. A series of alloys were prepared by adding 4, 6, 8, 10, wt% Mg in Al-4.5 (wt%) Cu-3.4 (wt%) Fe alloy. Microstructures were observed by optical microscopy. Mechanical properties like ultimate tensile strength, % elongation, % area reduction, hardness and wear test were determined. The study revealed that Mg transformed the needles of Al3Fe into globular shape which gave the alloys better mechanical properties.