Interfacial reactions between Sn-2.5Ag-2.0Ni solder and electroless Ni(P) deposited on SiC_p/Al composites

A novel Sn-2.5Ag-2.0Ni alloy was used for soldering SiCp/Al composites substrate deposited with electroless Ni(5%P) (mass fraction)and Ni(10%P)(mass fraction)layers.It is observed that variation of P contents in the electroless Ni(P)layer results in different types of microstructures of SnAgNi/Ni(P)solder joint.The morphology of Ni3Sn4 intermetallic compounds(IMCs)formed between the solder and Ni(10%P)layer is observed to be needle-like and this shape provides high speed diffusion channels for Ni to diffuse into solder that culminates in high growth rate of Ni3Sn4.The diffusion of Ni into solder furthermore results in the formation of Kirkendall voids at the interface of Ni(P)layer and SiCp/Al composites substrate.It is observed that solder reliability is degraded by the formation of Ni2SnP,P rich Ni layer and Kirkendall voids.The compact Ni3Sn4 IMC layer in Ni(5%P)solder joint prevents Ni element from diffusing into solder,resulting in a low growth rate of Ni3Sn4 layer.Meanwhile,the formation of Ni2SnP that significantly affects the reliability of solder joints is suppressed by the low P content Ni(5%P)layer.Thus,shear strength of Ni(5%P) solder joint is concluded to be higher than that of Ni(10%P)solder joint.Growth of Ni3Sn4 IMC layer and formation of crack are accounted to be the major sources of the failure of Ni(5%P)solder joint.

Choice of reference surfaces for machined surface roughness in milling of SiC_p/Al composites

In order to choose the appropriate reference surface on the machined surface roughness of Si Cp/Al composites, the cutting experiments of Si Cp/Al composites were carried out, and the machined surface topography was measured by OLS3000 Confocal laser scanning microscope. The 3D measured data of machined surface topography were analyzed by the area power spectrum density. The result shows that the texture of machined surface topography in milling of Si Cp/Al composites is almost isotropic. This is the reason that the values of Rq at different locations on the same machined surface are obviously different. Through the comparison of performance of different filtering methods, the robust least squares reference surface can be used to extract the surface roughness of SiC p/Al composites effectively.

Interfacial reaction control during pulsed argon arc welding of SiC_p/Al composites

The interfacial reaction control of SiC_p/2124Al composites was investigated during pulsed argon arc welding. Meanwhile, the mechanical properties, the metallographic structure and interfacial microstructure of the induced welding joint were tested and detected, respectively. The results reveal that the joint with excellent properties could be achieved by the proper selection of the special filling material and the addition of the pulse during welding. Moreover, the formation mechanism of the welding joint was discussed and the corresponding measures on further improving the quality of the welding joint of SiC_p/2124Al composites were put forward in the condition of pulsed argon arc welding.

ULTRASONIC VIBRATION LIQUID CAST SiC_w/Al AND SiC_p/Al COMPOSITES

SiC_w Al and SiC_p/Al composites have been produced by an uhrasonic vibration casting technique. Ultrasound irradiation promoted the wetting of reinforcements in aluminum liquid, improved the reinforcement distribution in the metal matrix, and reduced porosity. The composites can be remelted. Initial studies of the preparation procedures, microstructure, fracture surface morphology and remelting properties of SiC_w/Al and SiC_p/Al composites fabricated by ultrasonic vibration liquid are presented in this work.

Infiltration kinetics of pressureless infiltration in SiC_p/Al composites

The pressureless infiltration kinetics was investigated by plotting the infiltration distance as function of the infiltration time. The effects of key process parameters such as time, temperature, Mg content on the pressureless infiltration of silicon carbide particle compacts were studied and quantified. The preform with high volume fraction SiC was obtained by mixing SiC particles with bimodal size distribution, whose diameters are 5 and 50 μm, respectively. The results show that an incubation period exists before infiltration, the influence of temperature on the incubation time exceeds that of Mg content, infiltration rate increases with the increasing temperature and Mg content, infiltration rate decreases as Mg consumes. A model of macroscopical infiltration and microscopical infiltration of liquid alloy in porous SiC preform was proposed.

Laser-weldable Si_p-SiC_p/Al hybrid composites with bilayer structure for electronic packaging

Laser-weldable Sip-SiCp/Al hybrid composites with high volume fraction （60%-65%） of SiC reinforcement were fabricated by compression moulding and vacuum gas pressure infiltration technology. Microscopic observation displayed that the Sip-SiCp/Al hybrid composites with bilayer structure were compact without gas pores and the intergradation between Sip/Al layer and SiCp/Al layer was homogeneous and continuous. Further investigation revealed that the Sip-SiCp/Al hybrid composites possessed low density （2.96 g/cm^3）, high gas tightness （1.0 mPa·cm^3）/s）, excellent thermal management function as a result of high thermal conductivity （194 W/（m·K） and low coefficient of thermal expansion （7.0×10^-6 K-1）. Additionally, Sip-SiCp/Al hybrid composites had outstanding laser welding adaptability, which is significantly important for electronic packaging applications. The gas tightness of components after laser welding （48 mPa·cm^3）/s） can well match the requirement of advanced electronic packaging. Several kinds of these precision components passed tests and were put into production.

Effect of Ni content on the wear behavior of Al-Si-Cu-Mg-Ni/SiC particles composites

In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composites,particularly at elevated temperat-ures,remains an understudied area.In this study,Al-Si-Cu-Mg-Ni/20wt%SiC particles(SiCp)composites with varying Ni contents were prepared by using a semisolid stir casting method.The effect of Ni content on the dry sliding wear behavior of the prepared compos-ites was investigated through sliding tests at 25 and 350℃.Results indicated that theθ-Al_(2)Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt%to 3wt%.This change was accompanied by the formation and increase inδ-Al_(3)CuNi andε-Al_(3)Ni phases in microstructures.The hardness and ultimate tensile strength of the as-cast composites improved,and the wear rates of the composites decreased from 5.29×10^(−4)to 1.94×10^(−4)mm^(3)/(N∙m)at 25℃and from 20.2×10^(−4)to 7×10^(−4)mm^(3)/(N∙m)at 350℃with the increase in Ni content from 0wt%to 2wt%.The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites.However,the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of theε-Al_(3)Ni phase.Abrasive wear,delamination wear,and oxidation wear were the predominant wear mechanisms of the investigated composites at 25℃,whereas delamination wear and oxid-ation wear were dominant during sliding at 350℃.

Damping properties and mechanism of aluminum matrix composites reinforced with glass cenospheres

The damping properties were improved by preparing Al matrix composites reinforced with glass cenospheres through the pressure infiltration method.Transmission electron microscopy and scanning electron microscopy were employed to characterize the microstructure of the composites.The low-frequency damping properties were examined by using a dynamic mechanical thermal analyzer,aiming at exploring the changing trend of damping capacity with strain,temperature,and frequency.The findings demonstrated that the damping value rose as temperature and strain increased,with a maximum value of 0.15.Additionally,the damping value decreased when the frequency increased.Dislocation damping under strain and interfacial damping under temperature served as the two primary damping mechanisms.The increase in the density of dislocation strong pinning points following heat treatment reduced the damping value,which was attributed to the heat treatment enhancement of the interfacial bonding force of the composites.

Microstructure,interfacial reaction behavior,and mechanical properties of Ti_(3)AlC_(2)reinforced Al6061 composites

The interfacial reaction behavior of Al and Ti_(3)AlC_(2)at different pouring temperatures and its effect on the microstructure and mechanical properties of the composites were investigated.The results show that the addition of3.0 wt.%Ti_(3)AlC_(2)refines the average grain size ofα(Al)in the composite by 50.1%compared to Al6061 alloy.Morphological analyses indicate that an in-situ Al_(3Ti)transition layer of-180 nm in thickness is generated around the edge of Ti_(3)AlC_(2)at 720℃,forming a well-bonded Al-Al_(3Ti)interface.At this processing temperature,the ultimate tensile strength of A16061-3.0 wt.%Ti_(3)AlC_(2)composite is 199.2 MPa,an improvement of 41.5%over the Al6061 matrix.Mechanism analyses further elucidate that 720℃is favourable for forming the nano-sized transition layer at the Ti_(3)AlC_(2)edges.And,the thermal mismatch strengthening plays a dominant role in this state,with a strengthening contribution of about 74.8%.

Microstructure evolution,mechanical properties and fracture behavior of Al-xSi/AZ91D bimetallic composites prepared by a compound casting

In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically.The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer(MRL),whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites,while the hypereutectic Al-Si/AZ91D composites were opposite.The MRL included eutectic layer(E layer),intermetallic compound layer(IMC layer)and transition region layer(T layer).In the IMC layer,the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg_(2)Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides,increasing Si content,the thickness proportion of the T layer increased,forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content,and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa,which was 73.4% higher than the Al-6Si/AZ91D composite.The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content.The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg_(2)Si particle reinforcement,the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.

Evolution of Thermoplastic Shear Localization and Related Microstructures in Al/SiC_p Composites Under Dynamic Compression

The localized shear deformation in the 2024 and 2124 Al matrix composites reinforced with SiC particles was investigated with a split Hopkinson pressure bar (SHPB) at a strain rate of about 2.0×103 s-1. The results showed that the occurrence of localized shear deformation is sensitive to the size of SiC particles. It was found that the critical strain, at which the shear localization occurs, strongly depends on the size and volume fraction of SiC particles. The smaller the particle size, the lower the critical strain required for the shear localization. TEM examinations revealed that Al/SiCp interfaces are the main sources of dislocations. The dislocation density near the interface was found to be high and it decreases with the distance from the particles. The Al matrix in shear bands was highly deformed and severely elongated at low angle boundaries. The AI/SiCp interfaces, particularly the sharp corners of SiC particles, provide the sites for microcrack initiation. Eventual fracture is caused by the growth and coalescence of microcracks along the shear bands. It is proposed that the distortion free equiaxed grains with low dislocation density observed in the center of shear band result from recrystallization during dynamic deformation.

Wear mechanism for spray deposited Al-Si/SiC_p composites under dry sliding condition

Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10-220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

Effect of porosity and interface structures on thermal and mechanical properties of SiC_p/6061Al composites with high volume fraction of SiC

50 vol.% SiCp/Al composites with high thermal and mechanical properties were successfully produced by spark plasma sintering technique. The influences of sintering temperature on the thermal conductivity, coefficient of thermal expansion and bending strength of the SiCp/Al composites were carefully investigated. The results show that the SiCp/Al composites sintered at 520℃ exhibits a thermal conductivity of 189 W/(m·K), a coefficient of thermal expansion (50.200℃) of 10.03×10^-6 K^-1 and a bending strength of 649 MPa. The high thermal and mechanical properties can be ascribed to the nearly full density and the well interfacial bonding between the alloy matrix and the SiC particles. This work provides a promising pathway for producing materials to meet the needs of high performance electronic packaging.

Research on the Characters of the Cutting Force in Vibration Cutting Particle Reinforced Metal Matrix Composites SiC_p/Al

In this paper, turning experiments of machining particle reinforced metal matri x composites(PRMMCs) SiC p/Al with PCD tools have been carried out. The cutting force characteristics in ultrasonic vibration turning compared with that in com mon turning were studied. Through the single factor experiments and multiple fac tor orthogonal experiments, the influences of three kinds of cutting conditions such as cutting velocity, amount of feed and cutting depth on cutting force were analyzed in detail. Meanwhile, according to the experimental data, the empirica l formula of main cutting force in ultrasonic vibration turning was conclude d. According to the test results, the cutting force is direct proportion to cutt ing depth basically according to the relation between cutting force and other fa ctors, which is similar to that of common cutting, so is the feed rate, but the influence is not so big. The influence of cutting speed is larger than that of f eed rate on cutting force because the efficient cutting time increases in vibrat ion cycle with the increase of cutting speed, which causes cutting force to incr ease. The research results indicate: (1) Ultrasonic vibration turning possesses much lower main cutting force than that in common turning when adopting smaller cutting parameters. If using larger cutting parameters, the difference will inco nspicuous. (2) There are remarkable differences of cutting force-cutting veloci ty characteristics in ultrasonic vibration turning from that in common turning m ainly because built-up edge does not emerge in ultrasonic turning unlike common turning in corresponding velocity range. (3) In ultrasonic vibration cutting, t he influence of cutting velocity on cutting force is most obvious among thre e cutting parameters and the influence of feed is smallest. So adopting lower cu tting velocity and larger cutting depth not only can reduce cutting force effect ively but also can ensure cutting efficiency. (4) The conclusions are useful in precision and super precision manufacturing thin-wall pieces.

Tensile behavior of SiC_p/2124Al composites with various SiC particle sizes at room temperature

The tensile properties of 2124Al alloy composites reinforced with various sizes of SiC particles were investigated at room temperature. The size of SiC p was changed from 0.2 μm to 48.0 μm with an identical volume fraction of 20%. The results show that the relative density of the composite decreased with increase of the SiC p size from 3.0 μm to 48.0 μm, whereas 0.2 μm SiC p reinforced composite has the lowest relative density. The pore density, interparticle spacing, SiC particle cracking, SiC p/Al interfacial debonding, the distribution of SiC particles, in the composites are considered as factors to determine the failure behavior of the composites. [

Corrosion Behavior of SiC_p/2024 Al Matrix Composites in 3.5 wt pct Sodium Chloride

The influences of volume fraction and particle size of SiC particulate reinforcements on the corrosion characteristics of SiCp/2024 Al metal matrix composites in aerated 3.5 wt pct NaCI aqueous solution were investigated. The electrochemical behavior was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy, the general corrosion behavior of the composites was studied further by immersion tests. The results showed that pitting susceptibility was about the same for the composites and the alloy. The corrosion potentials were also independent of SiC phase. The corrosion resistance for the composites decreased as the volume fraction increased or particle size decreased.

Investigation of Al-based Alloys for Brazing SiC_p/Al Composites

The brazing of SiCp/Al composites is limited owing to the unavailability of suitable commercial intermediate temperature brazes. Adding a third constituent of copper to aluminum-silicon brazing alloy can depress the melting point sharply. While, it generates a large volume fraction of the hard Al2Cu intermetallic compounds (IMCs), which makes the alloy brittle and reduces its corrosion resistance. A quaternary addition of nickel that partly substitute for copper can refine grain size significantly, improve the mechanical properties, and without altering the melting range of aluminum-silicon-copper alloy. Al-Cu-Ni-Si braze alloy has been prepared and a fluxless process has been employed to braze SiCp/Al composites that leads to a good bonding strength of brazing joint.

Research on the Surface Micro-configuration in Vibration Cutting Particle Reinforced Metallic Matrix Composites SiC_p/Al

The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.

Preparation of SiC_p/Al_2O_3-Al Composites by Directed Metal Oxidation

SiCp/Al2O3-Al composites were synthesized by means of direct metal oxidation method. The composition and microstructures of the composites were investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM） and metallurgical microscope. The effects of technical parameters on the properties of the product were analyzed. The results indicate that the composite possesses a dense microstructure, composed of three interpenetrated phases. Of them, SiO2 layer prohibits the powdering of the composites; Mg promotes the wetting and infiltration of the system and Si restricts the interfacial reaction while improving the wetting ability between reinforcement and matrix.

Rolling of Al-SiC_p Composites

Aluminum based metal matrix composites are offering o utstanding properties in a number of automotive and aircraft components and body structures. The major advantages of these composite materials are their high st rength to weight ratio, high stiffness, high hardness, wear resistance, low coef ficient of thermal expansion, superior dimensional stability and versatility to designer. In addition to these their isotropic properties, good forming characte ristics, easy availability of cheaper reinforcements along with the availability of comparatively low cost, high volume production methods have made them a prom ising material for future growth. Weight reduction is a major goal of automotive innovations. Lighter vehicles/ ai rcraft means less fuel consumption, reduced emissions, and improved performance. Components made from highly loaded aluminium matrix composites are attractive r elative to iron based materials because of their low density, high stiffness (eq uivalent to nodular iron) and better heat transfer characteristics. The basic co st of materials is higher with these advanced composites; however, manufacturing the part to near net shape may offset basic material costs. A good aluminium based material design can improves safety. The aluminium-based composites can give cars better acceleration and braking, improved handling, ex cellent durability, and ease of repair. Tha aluminum-based composite performs a s well or better in crash than conventional steel-structured cars because of th eir larger volume, which can absorb more crash energy. Another excellent advanta ge of Al-SiC p composite in auto design is better stability and response, and reduced noise, vibration/harshness (NHV). These advantages stem from reduced veh icle weight combined with high structural stiffness and also lead to improved st ability and turning response. In the present work Al-SiC p composite plates of 10 to 12 mm thickness w ere cast using sand casting as well as die casting process. The plates were furt her machined to 3 to 4 mm thicknesses. The machined plates were subjected to col d as well hot rolling. The cold rolling of Al-3 wt.% SiC composite plates was done on 2 high experimental cold rolling mill at Indian Oil Corporation Ltd., R esearch and Development centre, Faridabad. For hot rolling, the Al-5 weight % SiC p composite plates were heat treated at 500 ℃ temperature and Al-15 weight % SiC p composite plates were heat treate d at 550 ℃ temperature for 20 minutes. The plates were hot rolled on 2 high ro lling mill of one ton capacity at IIT Delhi. The maximum percentage reduction ob tained after hot rolling of Al-5 weight % SiC p composite and Al- 15 weight % SiC p composite plates for 10 passes was 11 % and 6 % respectively. During col d rolling of Al-SiC p composites cracks (particle fracture) were observed due to the low ductility of Al-SiC p composties at room temperature. The various m echanical properties such as tensile strength, hardness and wear resistance were measured for the rolled and un-rolled Al-SiC p composite plates. The tensile strength of un-rolled and rolled Al-5wt.% SiC p composites are shown in Tab. 1. Table shows that the tensile strength decreases after rolling. This may be du e to the damage of the bonding between aluminum and silicon carbide particulates . The Rockwell hardness values of Al-5 wt.% SiC p composites measured before a nd after hot rolling are shown in Tab.2. The hardness was found to decrease afte r hot rolling, which may be due to the annealing of composites during heating. T he Rockwell hardness values of Al-3 wt.% SiC p composites before and after cold rolling are shown in Tab.3. The Table shows that the Rockwell hardness of Al-SiC p compostes increases after cold rolling due to the workhardening effec t. The wear resistance of rolled and un-rolled Al-SiC p composites were teste d on reciprocating ball on flat wear testing machine. The wear resistance of Al -SiC p composites decreases after hot rolling due to decrease in hardness