Effect of rolling and heat treatment on tensile behaviour of wrought Al-SiCp composites prepared by stir-casting

Al 6061- and Al 7108-SiCp composites (Al-PMMC) were prepared by stir-casting with SiCp size of 8 and 15 μm and volume fraction (Vf) of 0–20%. These composites were then subjected to successive hot rolling at 450 °C using a strain rate of 1 s⁻¹ while the intermediate period of heating between each two successive rolling steps was 1 min to 1 h. Tensile test was conducted on the as-rolled composite strips with 3.0, 1.1 and 0.4 mm thicknesses using 81, 94 and 98% reductions, subsequently, with a tensile rate of 10 MPa s⁻¹. Different tensile properties including ultimate tensile strength UTS, Young's modulus and elongation, were determined. The tensile behaviour was analysed in view of matrix alloy type and SiCp size and Vf. The effect of T6 treatment on the microstructure and tensile properties was also presented. Generally, successive hot rolling resulted in decreasing casting defects such as void and SiCp agglomeration present in the as-cast composites and hence enhanced mechanical properties were achieved. Almost 240 and 390% improvement in ultimate tensile strength (UTS) for 6061 and 7108 composite was obtained, respectively. The improvement in strength was remarkable for composites rolled to 0.4 mm. Annealing improved the elongation% at break of the 10–15% Vf composite more than 3 times. UTS of rolled composite was enhanced by T6 treatment at 176 °C and 120 °C for 6061 and 7108 composites. The effect of T6 treatment on the composite tensile behaviour was discussed.     

Friction and wear behaviors of reciprocatingly extruded Al–SiC composite

This study focuses on the friction and wear behaviors of reciprocatingly extruded Al–SiC composites. To increase the strength of metal matrix composites and refine the grains of the matrix some deformation processes can be applied, such as reciprocating extrusion (RE). For this reason, RE was carried out on a 6061 Al matrix by a SiC (20 μm) reinforced composite one. The billets were extruded under a pressure of 17.5 MPa at 573 K with a 10:1 extrusion ratio. The reciprocating extrusions were carried out by using up to 15 passes.     

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiC_p particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiC_p/Al composites. Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing, hot extrusion and heat treatment. The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti₅Si₃ phases at the interface. Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles. The microstructure, relative density and mechanical properties of the composite are significantly improved. When the volume fraction is 15%, the hardness, fracture strain and tensile strength of the SiC_p reinforced Al 2519 composite after Ti plating are optimized, which are HB 138.5, 4.02% and 455 MPa, respectively.     

搅拌铸造SiC_p/A356复合材料的显微组织及力学性能

采用搅拌铸造技术制备质量分数为15%的SiCp增强A356铝基复合材料,并对所制备的复合材料进行后续热挤压变形。通过金相观察(OM),扫描电镜(SEM)及力学性能测试等手段,对该复合材料显微组织与力学性能进行了研究。结果表明,所制备的复合材料铸态组织中,SiCp较均匀地分布于基体中,SiCp与Al界面处存在Si原子的富集;热挤压变形后,显微气孔等铸造缺陷明显减少,材料致密度显著提高,SiCp沿热挤压方向呈流线分布特征,颗粒均匀分散性明显提高;采用535℃×5h固溶+180℃×5h时效处理后,热挤压棒材的力学性能为:σs=370MPa,σb=225MPa,δ=5.3%,时效后析出强化相大小约为200nm,且弥散分布于基体中;断口分析表明,SiCp/A356铝基复合材料的断裂主要是由基体的塑性断裂及SiCp的断裂导致的。     

T6热处理对Al+SiC预制颗粒增强ZL101/ZL101-Mg基复合材料组织和力学性能影响的研究

通过半固态搅拌铸造的方法制备了Al+SiC预制颗粒增强ZL101基及ZL101-Mg基复合材料,研究了T6热处理对该复合材料微观组织及力学性能的影响。结果表明,T6热处理对Al+SiC预制颗粒增强ZL101基复合材料和Al+SiC预制颗粒增强ZL101+Mg基复合材料中SiC颗粒的分布没有明显影响。但T6热处理使Al+SiC预制颗粒增强ZL101复合材料中共晶硅细化,Al+SiC预制颗粒增强ZL101+Mg复合材料中共晶硅长大变粗。T6热处理对Al+SiC预制颗粒增强ZL101复合材料抗拉强度的平均提升率达到了54.44%,对其伸长率的平均提升率为5.47%。对Al+SiC预制颗粒增强ZL101+Mg复合材料抗拉强度的平均提升率为13.52%,对其伸长率的平均提升率为31.5%。     

预分散对SiCp/Al复合材料微观组织均匀性的影响

采用液态搅拌法制备SiCp/ZL105复合材料,研究预分散措施对SiCp/Al复合材料微观组织均匀性的影响规律.试验结果表明,在其他条件相同的情况下,采用预分散措施,可明显改善SiC颗粒在Al基体中分布的均匀性.     

热挤压变形对搅拌铸造SiCp/2024复合材料显微组织与力学性能的影响

利用搅拌铸造?热挤压工艺制备SiCp/2024复合材料板材。通过金相观察(OM)、扫描电镜(SEM)及力学性能测试等手段研究了该复合材料热挤压变形前后的显微组织与力学性能。结果表明,复合材料铸坯主要由大小为80μm~100μm的等轴晶组成,晶界第二相粗大呈非连续状分布,SiC颗粒较均匀地分布于基体合金,大部分SiC颗粒沿晶界分布,少数颗粒分布于晶内;热挤压变形后,显微孔洞等铸造缺陷和SiC颗粒团聚现象明显消除,SiC颗粒及破碎的第二相沿热挤压方向呈流线分布,复合材料的强度和塑性显著提高;拉伸断口表明,热挤压变形有利于改善SiC颗粒与基体合金的界面结合;SiCp/2024复合材料主要的断裂方式为SiC颗粒断裂和SiC/Al的界面脱粘。     

Processing and compressive strength of Al–Li–SiCp composites fabricated by a compound billet technique

Al–Li–SiC_p composites were fabricated by a simple and cost effective stir casting technique. A compound billet technique has been developed to overcome the problems encountered during hot extrusion of these composites. After successful fabrication hardness measurement and room temperature compressive test were carried out on 8090 Al and its composites reinforced with 8, 12 and 18 vol.% SiC particles in as extruded and peak aged conditions. The addition of SiC increases the hardness. 0.2% proof stress and compressive strength of Al–Li–8%SiC and Al–Li–12%SiC composites are higher than the unreinforced alloy. In case of the Al–Li–18%SiC composite, the 0.2% proof stress and compressive strength were higher than the unreinforced alloy but lower than those of Al–Li–8%SiC and Al–Li–12%SiC composites. This is attributed to clustering of particles and poor interfacial bonding.     

Centrifugal casting of functionally graded aluminium matrix composite components

Abstract

Centrifugal casting is one of the potential manufacturing techniques used for producing near net shaped components with improved properties. The emergence of new class of functionally graded materials has made it an important technique for the fabrication of engineering components and structures with graded property. The present paper describes the studies carried out on processing and characterisation of functionally graded Al matrix composites components based on Al–SiC ex situ and Al–Si in situ composites. The microstructural and mechanical characteristics of the composites are evaluated. In the case of Al–SiC functionally graded metal matrix composites discs, the particles are segregated gradiently towards the outer periphery of the casting exhibiting high strength and hardness towards the outer periphery. The Al–Si in situ composite cylinder shows the dispersion of primary Si particles towards the inner periphery of the casting which can lead to higher hardness and wear resistance.     

Microstructure and mechanical properties of Mg-Al-Mn-Ca alloy sheet produced by twin roll casting and sequential warm rolling

Microstructural evolution and mechanical properties of twin roll cast (TRC) Mg-3.3 wt.%Al-0.8 wt.%Mn-0.2 wt.%Ca (AM31 + 0.2Ca) alloy strip during warm rolling and subsequent annealing were investigated in this paper. The as-TRC alloy strip shows columnar dendrites in surface and equiaxed dendrites in center regions, as well as finely dispersed primary Al₈Mn₅ particles on interdendritic boundaries which result in the beneficial effect on microstructural refinement of strip casting. The warm rolled sheets show intensively deformed band or shear band structures, as well as finely and homogeneously dispersed Al-Mn particles. No evident dynamic recrystallization (DRX) takes place during warm rolling process, which is more likely attributed to the finely dispersed particle and high solid solution of Al and Mn atoms in α-Mg matrix. After annealing at 350 °C for 1 h, the warm rolled TRC sheets show fine equiaxed grains around 7.8 μm in average size. It has been shown that the present TRC alloy sheet has superior tensile strength and comparative elongation compared to commercial ingot cast (IC) one, suggesting the possibility of the development of wrought magnesium alloy sheets by twin roll strip casting processing. The microstructural evolution during warm rolling and subsequent annealing as well as the resulting tensile properties were analyzed and discussed.     

Abrasive wear behavior of Ni-P coated Si3N4 reinforced Al6061 composites

Ni-P coated Si₃N₄ reinforced Al6061 composites were fabricated by vortex method. Percentage of reinforcement was varied from 6 wt.% to 10 wt.% in steps of 2. Cast matrix alloy and developed composites were hot forged at a temperature of 500 °C using a 300T hydraulic hammer. Both as cast and hot forged matrix alloy and its composites were subjected to microstructure studies, grain size analysis, microhardness and abrasive wear tests. Microstructure studies reveal uniform distribution of silicon nitride particles with good bond between matrix and reinforcement in both as cast and hot forged condition. It is observed that, increased content of reinforcement in both as cast and hot forged composites do result in significant grain refinement. However, when compared with as cast matrix alloy and its composites hot forged alloy and its composites exhibits higher extent of grain refinement. Both as cast and hot forged composites exhibit improved microhardness and abrasive wear resistance when compared with the unreinforced alloys under identical test conditions. Abraded worn surfaces were examined using scanning electron microscopy (SEM) for possible wear mechanisms. Increased abrasive particle size and load has resulted in larger extent of grooving leading to increased abrasive wear loss for both the matrix alloy and developed composites.     

Effects of SiC volume fraction and aluminum particulate size on interfacial reactions in SiC nanoparticulate reinforced aluminum matrix composites

The SiC nanoparticulate reinforced Al-3.0 wt.% Mg composites were fabricated by combining pressureless infiltration with ball-milling and cold-pressing technology at 700 °C for 2 h. The effects of SiC nanoparticulate volume fractions (6%, 10% and 14%) and Al particulate sizes (38 μm and 74 μm) on interfacial reactions were investigated by SEM, TEM and X-ray diffraction. The results show that the MgO at the interface between SiC nanoparticulate and molten Al can provide a barrier for the diffusion of Si, C and Al. Using Al particulate (74 μm) as raw material, the Al₄C₃ phase was not found in the composites containing 6 vol.% and 10 vol.% SiC, but presented in the composites containing 14 vol.% SiC. When SiC content up to 14 vol.%, the products of MgO around SiC nanoparticulate are not enough to provide effective protection from the reaction between SiC and molten Al, therefore the diffusion of Si, C and Al can take place to produce Al₄C₃ and Si phases. Using 38 μm Al particulate as raw material, the fine Al particulate possesses the high reaction activity and can easily be embedded into the gap among the big Mg particulate segregated at the interface, resulting in the appearance of exposure surface of SiCp to the Al and the forming of diffusion channels for the atomics C, Si and Al. So, the formations of Al₄C₃ and Si phases were occurred.     

Friction stir processing of Al/SiC composites fabricated by powder metallurgy

Friction stir processing (FSP) was applied to modify the microstructure of sintered Al–SiC composites with particle concentrations ranging from 4 to 16 vol%. Two SiC particle sizes (490N and 800 grades) were examined. Following FSP, the hardness of the 4 and 8 vol% of 490N grade SiC composites increased from 130 HV and 145 HV to 171 HV and 177 HV respectively. The increase was accounted for by the severe deformation occurring during FSP which uniformly distributed the SiC particles. The composites containing 16 vol% SiC could not be fully consolidated using FSP, and contained residual pores and lack of consolidation which originated from the as-received sintered microstructure. The hardness correlated well with the mean inter-particle spacing for the SiC particles in the case of composites containing 4 and 8 vol% SiC.     

铸造ZL101A／SiCp复合材料的研究

采用真空搅拌复合工艺制备了铸造ZL101A／SiC复合材料,研究了变质和细化处理对复合材料组织的影响。结果表明：变质和细化处理铸造 ZL101A／SiC复合材料制备工艺的重要处理措施,可明显改善复合材料的组织。利用透射电镜对AL／SiC界面特征及界面反应进行分析,同时对该复合材料的铸造性能（熔体合金流动性能、线收缩、体收缩和热裂倾向）以及力学和物理性能进行了测试。     

An investigation on corrosion behaviour of pressure infiltrated Al-Mg alloy/SiCp composites

In this study, effect of Mg alloying addition (2-8 wt.%) on corrosion behaviour of Al matrix composites, in 3.5 wt.% NaCl environment, has been investigated. Composites were produced by pressure infiltration technique at 750 °C and had a SiC particle (SiC_p) volume fraction of ∼60%. Results were evaluated by using potentiodynamic polarisation measurements, immersion tests, SEM, EDS and XRD analysis. Compared to the pure Al matrix, mass loss of the composites decreased with increasing Mg content. Experimental results revealed that intermetallics as a result of reaction between Al-Mg alloy and SiC particle has beneficial effect on corrosion resistance of the composites due to interruption of the continuity of the matrix channels within the pressure infiltrated composites.     

Microstructure and mechanical properties of magnesium composites prepared by spark plasma sintering technology

Spark plasma sintering (SPS) technology was used to determine the appropriate conditions for SPS sintering of commercially pure magnesium as well as the magnesium alloy AZ31. It was found that the sintering temperatures of 585 °C and 552 °C were the most suitable sintering temperatures for the magnesium and the AZ31 alloy, respectively. Magnesium matrix and AZ31 alloy matrix composites reinforced with SiC particles were then successfully fabricated by the SPS method at sintering temperatures of 585 °C and 552 °C, respectively. A uniform distribution of SiC particles was observed along the boundary between matrix particles. The mechanical properties, i.e. hardness and tensile strength increased with increasing SiC content up to 10 wt%. However, when the SiC content was larger than 10 wt%, the tensile strength decreased due to the agglomeration of SiC particles. The agglomeration of SiC particles was found to lead to the degradation of the interfacial bonding strength between matrix and reinforcement.     

Influence of SiC Particles Distribution and Their Weight Percentage on 7075 Al Alloy

The stir casting method was used for fabrication of 7075 aluminum alloy with 10 wt.% SiC particles of size 20-40 μm. The research objective of this paper are to achieve uniform distribution of SiC particles in the 7075 aluminum alloy matrix, characterization, and analysis of mechanical properties of composite formed. Experiments were carried out at stirring speeds of 500, 650, 750 rpm, and stirring period of 10 min. Microstructures of aluminum alloy and composites with 5, 10 wt.% SiC reinforcements were examined. The results reveal that composite produced at stirring speed of 650 rpm and stirring time of 10 min has uniform distribution of SiC particles. XRD and EDAX analysis were carried out for 7075 Al alloy and composite with 10 wt.% SiC reinforcement. No adverse reaction was observed in XRD and EDAX of composite with 10 wt.% SiC reinforcement. Tensile strength and hardness increased by 12.74% and 10.48%, respectively, with the increase in percentage of SiC reinforcement from 5 to 15 wt.%.     

The effect of primary and secondary processing on the abrasive wear properties of compocast aluminum 6061 alloy matrix composites

In this present work, the compocasting method was used to produce Aluminum 6061 alloy matrix composites reinforced SiC particles with a variety of particle average sizes of 1, 5, 20 and 50 μm. The influences of particle volume fraction of metal matrix composites on the dry sliding wear behaviour have been investigated. The acceptable quality of the fabricated composites calls for a proper selection of process parameter such as pouring temperature, stirring speed, stirring time, preheat temperature of reinforcement, minimum level of the porosity and prevention of the chemical reaction between reinforcement and matrix. Experimental test was carried out on the porosity and hardness of the composites. A pin-on-disc wear test was used to assess the effect of SiC content, SiC size and secondary mechanical processing with different rolling reductions on wear characteristics of Al matrix composites. It is noted that the particle distribution in the cold rolled composites is much more uniform than the as-cast one.     

Enhanced mechanical properties in Al/diamond composites by Si addition

Diamond particles reinforced aluminum–silicon matrix composites,abbreviated as Al(Si)/diamond composites,were fabricated by squeeze casting.The effect of Si content on the microstructure and mechanical properties of the composites were investigated.The mechanical properties are found to increase monotonically with Si content increasing up to 7.0 wt%.The Al-7.0 wt% Si/diamond composite exhibits tensile strength of 78 MPa,bending strength of 230 MPa,and compressive strength of426 MPa.Al–Si eutectic phases are shown to connect with Al matrix and diamond particles tightly,which is responsible for the enhancement of mechanical properties in the Al(Si)/diamond composites.     

The effect of sintering temperature on some properties of Cu-SiC composite

Copper matrix composites reinforced with 1 wt.%, 2 wt.%, 3 wt.% and 5 wt.% SiC particles were fabricated by powder metallurgy method. Cu and Cu-SiC powder mixtures were compacted with a compressive force of 280 MPa and sintered in an open atmospheric furnace at 900-950 °C for 2 h. Within the furnace compacted samples were embedding into the graphite powder. The presence of Cu and SiC components in composites was verified by XRD analysis. Optical and SEM studies showed that Cu-SiC composites have a uniform microstructure in which silicon carbide particles are distributed uniformly in the copper matrix. The results of the study on mechanical and electrical conductivity properties of Cu-SiC composites indicated that with increasing SiC content (wt.%), hardness increased, but relative density and electrical conductivity decreased. The highest electrical conductivity of 98.8% IACS and relative density of 98.2% were obtained for the Cu-1 wt.%SiC composite sintered at 900 °C and this temperature was defined as the optimum sintering temperature.