Gravity Casting Technique Research Articles

Analysis of the Quality of Incoming AlSi9Mn Alloy Ingots

Previous research revealed that the quality of the ingots produced by different primary or secondary alloy suppliers can differ remarkably. In this way, the quality of the liquid metal and the castings produced from it can be affected by the impurity content of the ingots used as charge material. In this work, a modified reduced pressure test (RPT) technique, which is based on the remelting of samples extracted from ingots, was applied to investigate the quality of primary AlSi9Mn ingots made by horizontal direct-chill (HDC) casting and gravity casting techniques. For the evaluation of metal quality, image analysis of the cross sections was applied. Pore area fraction, number density, normalized bifilm index, and normalized total pore perimeter were determined, and the relationships between the different metrics were analyzed. The results were compared with the melt quality assessment of the as-melted batches made from the ingots. Solidification simulations, thermal analysis, and microstructural investigations were conducted to investigate the solidification conditions of traditional and remelted RPT samples. Based on the results, the HDC cast ingots possess lower oxide and gas concentrations, which can be traced back to the differences in the melt preparation and casting technologies of the ingots. The comparison of the parameters evaluated by image analysis revealed that there is a strong linear relationship between normalized bifilm index and normalized total pore perimeter. The possible sources of error in ingot quality evaluation are highlighted.

Study on the fabrication and performance of 3D-Network SiC/Cu composites

ABSTRACT 3D-Network SiC ceramic was prepared using a polymer sponge replica technique with SiC ceramic slurry (77 wt% solid content). The triangular hole defects in 3D-Network SiC ceramic were reduced and the mechanical properties were improved by high-pressure spraying and vacuum infiltration. The 3D-Network SiC/Cu composite material was fabricated by the gravity casting technique, and the interfacial bonding and abrasion resistance of the composites were tested and analyzed. The results show that the compressive strength of high-pressure sprayed 3D-Network SiC ceramic increased slightly from 0.67 Mpa to 0.74 Mpa due to the triangular hole defects left when the polymer sponge was decomposed at high temperatures. The mechanical properties of 3D-Network SiC ceramics that have been vacuum infiltrated in alumina and a mixture composed of alumina and andalusite were greatly improved, and their compressive strength was increased to 1.02Mpa and 1.57Mpa, respectively. The interface between SiC and Cu in the 3D-Network SiC/Cu composites prepared by different processes shows excellent bonding, and the abrasion resistance of the 3D-Network SiC/Cu composites prepared by different processes was 2.02–9.18 times that of pure copper respectively.

Grain characteristics, electrical conductivity, and hardness of Zn-doped Cu\u20133Si alloys system

The grain characteristics, electrical conductivity, hardness, and bulk density of Cu–3Si–(0.1—1 wt%)Zn alloys system fabricated by gravity casting technique were investigated experimentally using optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The study established the optimal alloy composition and the significance of zinc addition on the tested properties using response surface optimal design (RSOD). The cooled alloy samples underwent normalizing heat treatment at 900 °C for 0.5 h. The average grains size and grains distribution were analyzed using the linear intercept method (ImageJ). The microstructure examination revealed a change in grain characteristics (morphology and size) of the parent alloy by addition of 0.1 wt% zinc. The average grains size of the parent alloy decreased from 12 µm to 7.0 µm after 0.1 wt% zinc addition. This change in grain characteristics led to an increase in the hardness of the parent alloy by 42.2%, after adding 0.1 wt% zinc. The electrical conductivity of the parent alloy decreased from 46.3%IACS to 45.3%IACS, while the density was increased by 8.4% after adding 0.1 wt% zinc. The statistical data confirmed the significance of the change in properties. The result of optimization revealed Cu–3Si–0.233Zn as the optimal alloy composition with optimal properties. The Cu–3Si–xZn alloy demonstrated excellent properties suitable for the fabrication of electrical and automobile components.

Effect of Grain Modifier on Mechanical and Tribological Properties of Al-Si Alloy and Composite

This study investigates the effect of Strontium (Sr) grain modifier addition on Al-9Si alloy and B4C reinforced composite fabricated by two step gravity casting technique. The optimum level of Sr was identified as 0.08 wt.% for complete modification. The modified cast components were thermally treated by T6 temper to enhance the tribo-mechanical properties. Metallographic observation revealed the transformation of acicular Si grains to fine fibrous in as-cast condition, which later transformed to spheroidised eutectic Si after heat treatment. The combined effect of grain modification by Sr and the influence of spheroidised eutectic Si enhanced the mechanical properties. Heat treated modified composite exhibited superior tribological properties when compared to other components under varying applied normal loads and sliding distances. Worn mechanism of heat treated modified composite was observed to be minor delamination wear regime at high load (55 N) and sliding distance (1500 m).

Lifetime simulation of traditional boat propellers using Ansys

In this study an age-predictive simulation of propellers used by traditional fishermen in the Indramayu region was carried out. These boats were driven by gasoline or diesel motors to drive boat propellers. This boat propeller is made of aluminum alloy with gravity casting technique. The problem is that there are many fishermen who fail on their propellers which generally occur faults on the propeller fins, the purpose of this study is to predict fatigue and age of propellers used in traditional boats, with the observation and calculation method of Finite Element Analysis (FEA) using Ansys software. The results of lifetime propeller analysis with variability in boat hull loading and boat load, with different variations between 3488N and 4788 N, obtained a lifetime for the loading did not experience a significant difference with a lifetime of 277,7 hours.

Dry reciprocating wear and frictional behaviour of B4C reinforced functionally graded and homogenous aluminium matrix composites

A comparative study was drawn for evaluating mechanical and tribological properties between as-cast, heat treated (HT) Functionally Graded (FG) A359/10wt% B4C and homogenous A359/6wt% B4C composites (wt% equivalent to FGM outer zone, determined by chemical dissolution method) processed through horizontal centrifugal and gravity casting techniques respectively. Metallographic analysis confirmed decreasing gradation of reinforcement particles from outer to inner layers for as-cast FG composite, whereas even distribution of reinforcement was observed throughout for homogenous composite. Formation of fine alpha-spheroidized eutectic silicon was observed in HT composite. Comparative analysis carried out for mechanical properties of as-cast to HT composite confirmed an improvement of 37.9 % for outer layer of FG composite and 32.6 % for homogeneous composite in micro-hardness, while an improvement of 24.1 % for outer layer FG composite and 5.6 % for homogeneous composite was observed for tensile strength. Reciprocating wear analysis confirmed superior resistance to wear for outer zone of HT FG composite, with an increasing trend for wear rate and friction co-efficient under the effect of load and sliding distance. A decreasing trend was observed for wear rate and friction co-efficient as weight percentage of reinforcement increased. Worn morphological analysis confirmed predominant delamination wear mechanism for homogenous composites, whereas a combination of abrasive, adhesive and delamination wear was observed for FG composite.

Effect of Bi addition on microstructure and mechanical properties of hypereutectic Al-17.6Si alloy

Al-17.6Si-XBi (X = 0.0, 0.5, 1.0, 1.5 and 2.0 wt%) alloys have been synthesized using gravity casting technique to study the influence of Bi concentration on the microstructure and mechanical properties of hypereutectic Al-17.6Si alloy. The as-cast unmodified hypereutectic Al-17.6Si alloy consists of irregular polygonal and plate-like primary Si (SiP) particles and irregular plate and rod-like shape, coarse eutectic Si (SiE). The Bi addition modifies and refines the SiP particles into small pentagonal shape particle with blunt corners. Volume fraction, average equivalent diameter and aspect ratio of the SiP particle decrease with increase in Bi concentration in the alloy. The bulk hardness of the alloys and micro-hardness of SiP particles are increased with increase in Bi concentration as the SiP particles became compact and finer. The microstructure modification also has a significant effect on the mechanical properties of the alloy. The ultimate tensile strength (UTS), yield strength (YS) and elongation (%El) increase with the increase in Bi concentration in the alloy. Further, fractographs reveal that the brittle mode of fracture decreases and ductile fracture with dimples formation increases due to the formation of finer SiP and SiEwith round corners.

Microstructural evolution and hardness property of in situ Al–Mg2Si composites using one-step gravity casting method

ABSTRACTIn the present investigation, Al–X wt-% Mg2Si (X = 0, 5, 10, 15 and 20) in situ composites are successfully synthesised by one-step gravity casting technique. Commercially pure Al, Mg and Si are used as raw materials. Microstructural evaluation and correlation of micro- and bulk hardness properties have been studied on developing composites. The composites consist of mainly three phases: matrix (α-Al), reinforcing (primary Mg2Si) and binary eutectic (Al–Mg2Si) phase. Primary Mg2Si particles are formed by pseudo-eutectic transformation during solidification and surrounded by matrix and binary eutectic phase. It is found that Mg2Si concentration has a significant impact on morphology and volume per cent of the above-mentioned phases. Primary Mg2Si particles’ size and volume per cent increase with increasing wt-% of Mg2Si. Volume per cent of individual phases and Mg2Si concentration have great impact on hardness properties of composites. Bulk hardness increases with increasing wt-% of Mg2Si concentration, but micro-hardness of primary Mg2Si particle decreases slightly. Mg2Si concentration also has significant impact on micro-hardness of individual phases.

Influence of Ca addition on microstructural evolution and mechanical properties of near-eutectic Mg–Li alloys by copper-mold suction casting

The influence of small amount of Ca addition on the microstructures and mechanical properties of three near-eutectic Mg-x Li (x = 6.8, 7.5, 8.4 wt. %) binary alloys under rapid solidification condition by using Copper-mould Suction Casting technique were investigated. The resultant microstructures were very distinct from those by conventional gravity casting technique in the morphology, grain size and the volume fraction of α-Mg phase. Mechanical properties of the Ca-modified Mg-x Li binary alloys were significantly enhanced. More interestingly, a eutectic growth mode transition from their regular divorced eutectic growth to the regular coupled eutectic structure was induced in Mg-8.4Li alloy via Ca addition. The eutectic transition mechanisms in three Mg-x Li alloys by Ca addition were discussed in terms of the freezing rate, Mg2Ca particle segregation, the relative volume fraction of α-Mg phase.

Tribological and thermomechanical analysis of CaO (quicklime) particulates filled ZA-27 alloy composites for bearing application

This research work investigates friction and wears behaviour of CaO filler / particulate reinforced ZA-27 alloy composites. Pin-on-disk tribometer confining to ASTM G 99 standard with EN-31 hardened steel disc was used to simulate the tribological performance experimentally. The tribological parameters were evaluated over a normal load range of 5–45 N, sliding velocity of 1.047–5.235 m/s., sliding distance of 500–2500 m, environment temperature of 25–45℃ and filler content range of 0–10 wt%. The various alloy composites were fabricated under vacuum environment by high-temperature gravity casting technique. The steady-state specific wear rate and coefficient of friction were evaluated under different boundary conditions and thereafter Taguchi design of experiment methodology was adopted to compute the experimental specific wear rate of the proposed alloy composites. The dynamic mechanical analysis and thermo-gravimetric analysis study were also performed in order to observe the thermal characteristics of the composites at higher temperature. Finally, the surface morphology of the worn samples was performed using field-emission scanning electron microscope to understand the wear mechanism prevailed at rubbing surfaces and then atomic force microscopy analysis was studied to evaluate the surface profile of the worn sample. At the end, energy-dispersive spectrometer analysis was also performed to find out the elemental compositions of the worn alloy composites.

Enhancement in tribological behaviour of functionally graded SiC reinforced aluminium composites by centrifugal casting

Enhanced tribological and location-specific properties achieved in functionally graded metallic composites make them potential materials for futuristic engineering components. The present investigation aims on the processing of homogenous and functionally graded Al matrix composites reinforced with SiC particles of 23 µm average particle size by gravity and centrifugal casting techniques. The sizes of the primary aluminium and eutectic silicon phases are finer towards the outer periphery due to the higher solidification rate. Functionally graded Al–SiCp composite rings produced by centrifugal casting show higher concentration of SiCp towards outer periphery, followed by a gradient transition region and the particle depleted zone. Particle agglomerates formed due to partially wetted particles associated with voids and gas porosities segregate towards the inner periphery. The higher concentration of reinforcement particles near the outer periphery in FGM enhances the hardness and wear resistance in rotary and reciprocating wear studies. Centrifugal cast alloys show enhanced wear resistance than the gravity cast specimen due to fine grains of primary aluminium and eutectic silicon. The rotary and reciprocating wear test shows the adhesive and abrasive type wear mechanisms.

Effect of Sphere Properties on Microstructure and Mechanical Performance of Cast Composite Metal Foams

Aluminum-steel composite metal foams (Al-S CMF) are manufactured using steel hollow spheres, with a variety of sphere carbon content, surface roughness, and wall porosity, embedded in an Aluminum matrix through gravity casting technique. The microstructural and mechanical properties of the material were studied using scanning electron microscopy, energy dispersive spectroscopy, and quasi-static compressive testing. Higher carbon content and surface roughness in the sphere wall were responsible for an increase in formation of intermetallic phases which had a strengthening effect at lower strain levels, increasing the yield strength of the material by a factor of 2, while higher sphere wall porosity resulted in a decrease on the density of the material and improving its cushioning and ductility maintaining its energy absorption capabilities.

Fabrication of metallic composite foam using ceramic porous spheres “Light Expanded Clay Aggregate” via casting process

Composite metal foam was produced as an advanced porous material, using gravity casting technique. Light Expanded Clay Aggregate “LECA” was used as space holder for the produced composite metal foam. The used LECA density was 0.33–0.43g/cm3 and the volume fraction of its porosity was from 73 to 88vol.% and aluminum A355.0 was selected as matrix in order to produce the composite foam. Structural characterization, relative density, hardness and compressive test were studied. The composite metal foam was well investigated and found to have homogeneous structure, relatively equal pore, distributable pore and isotropy properties. The study resulted in that relative density, yield strength and energy absorption capacity were 0.44, 35.9MPa and 18MJ/m3, respectively.

Effect of processing parameters on the microstructure and mechanical properties of Al–steel composite foam

Al–steel composite foams comprise of steel hollow spheres embedded in an aluminum matrix and are processed using a gravity casting technique. The effect of processing parameters such as casting temperature and cooling rate on the microstructure and mechanical behavior was studied to establish structure–property relationships. Results show that the amount and composition of intermetallic phases present in the foam microstructure is directly related to casting temperature and cooling rate. Highest strength and energy absorption were obtained from Al–steel foams with fast solidification rates that minimize the growth of intermetallic phases.

Sensitivity of different Al–Si alloys to centrifugal casting effect

This paper is concerned with the sensitivity of different Al–Si alloys to centrifugal effect of the vertical centrifugal casting technique on castings as compared to the traditional gravity casting technique. A comparison of mechanical properties of specimens obtained by both centrifugal casting technique and gravity casting technique is made on three different Al–Si alloys (from a hypoeutectic to a hypereutectic alloy). A microstructure analysis, in order to quantify the phase/constituent distribution along the gradation axis, is made to understand the relationship between constituents and mechanical properties for both casting techniques. It was verified that the centrifugal effect is very alloy dependent and may be substantially well correlated with the eutectic volume fraction of the alloy. It was also found that the centrifugal effect on mechanical properties is more is more pronounced in alloys with high eutectic contents.

Fatigue in aluminum–steel and steel–steel composite foams

The compression–compression fatigue behavior of two classes of composite metal foams (CMF) manufactured using different processing techniques, was investigated experimentally. Aluminum–steel composite foam processed using gravity casting technique comprises of steel hollow spheres and a solid aluminum alloy matrix. Steel–steel composite foam, processed using powder metallurgy (PM) technique consists of steel hollow spheres packed in a steel matrix. Under compression fatigue loading, the composite foam samples showed a high cyclic stability at maximum stress levels as high as 90 MPa. The deformation of the composite foam samples was divided into three stages – linear increase in strain with fatigue cycles (stage I), minimal strain accumulation in large number of cycles (stage II) and rapid strain accumulation within few cycles culminating in complete failure (stage III). Composite foams under cyclic loading undergo a uniform distribution of deformation, unlike the regular metal foams, which deform by forming collapse bands at weaker sections. As a result, the features controlling the fatigue life of the composite metal foams have been considered as sphere wall thickness and diameter, sphere and matrix materials, processing techniques and the bonding strength between the spheres and matrix.

Effect of Gravity/ Vibration/ Centrifugal Process on Mechanical Properties of an Al-Si Alloy

On this paper, a study that evaluates the influence of some variables on the mechanical properties of the vertical centrifugal casting is made. It is emphasized the fact that the centrifugal effect from vertical centrifugal casting brings special features on mechanical properties. It has been observed that the centrifugal effect may substantially increase, in some alloys, the rupture strength, rupture strain, and Young modulus, as compared to the gravity casting technique. When compared to gravity casting, the centrifugal casting process, besides the centrifugal force (pressure effect), always has an inherent associated vibration during the casting. In this study, as an attempt to isolate the vibration effect from the overall centrifugal effect, tests on castings obtained by vibrating gravity casting process are made. A comparison between castings obtained by centrifugal casting technique, vibrating casting technique and gravity casting technique is made in order to fully understand the features that allow the improvement on mechanical properties during the vertical centrifugal casting technique. An analysis of the most important effects, on both mechanical properties and on some metallurgical features is made.

A study on aluminum–steel composite metal foam processed by casting

Composite metal foam (CMF), a new material belonging to the class of advanced cellular and porous materials, has been processed using gravity casting technique for the first time at North Carolina State University. This material comprises of steel hollow spheres and a solid aluminum alloy matrix. The energy absorption behavior of the material under static compression has been studied extensively. Experimental results show that CMF not only has a higher energy absorption capability than that of other commercially available metal foams produced from similar materials, but also possess a higher strength to density ratio. The microstructural analysis of the material was used to study and explain the formation of different phases at the aluminum–steel interface and their effect on the deformation behavior of the foam under compression. As the result of high strength and strain rates, the increase in energy absorption of the composite metal foam samples observed ranges over 30 times compared to that of 100% Al foams and over twice compared to that of 100% steel foams.

New Composite Metal Foams under Compressive Cyclic Loadings

New composite metal foams are processed using powder metallurgy (PM) and gravity casting techniques. The foam is comprised of steel hollow spheres, with the interstitial spaces occupied by a solid metal matrix (Al or steel alloys). The cyclic compression loading of the products of both techniques has shown that the composite metal foams have high cyclic stability at very high maximum stress levels up to 68 MPa. Under cyclic loading, unlike other metal foams, the composite metal foams do not experience rapid strain accumulation within collapse bands and instead, a uniform distribution of deformation happen through the entire sample until the densification strain is reached. This is a result of more uniform cell structure in composite metal foams compared to other metal foams. As a result, the features controlling the fatigue life of the composite metal foams have been considered as sphere wall thickness and diameter, sphere and matrix materials, and processing techniques as well as bonding strength between the spheres and matrix.

Advantages of the centrifugal casting technique for the production of structural components with Al–Si alloys

This work discusses the mechanical properties advantages of using the vertical centrifugal casting technique for the production of structural components when compared to traditional gravity casting. An analysis of the most important features that occur in mechanical properties due to the centrifugal force is made. A comparison of mechanical properties of specimens obtained by both centrifugal casting technique and gravity casting technique is made. It is observed that the centrifugal force may increase rupture strength in ≈35%, and rupture strain in about 160% over the gravity casting technique. The Young modulus also increases in about 18%. The fatigue life experiences an increase of about 1.500% and the fatigue limit increases in about 45%. The centrifugal casting process is, therefore, much more effective in terms of obtained mechanical and fatigue properties as compared to gravity casting. The previous effects vary within the casting, according to the relative position from where the specimen is taken from the casting. The higher the distance in relation to the rotation centre (higher centrifugal force or higher G) the bigger the increase in mechanical properties. Thus, a functional graded material, with properties changing along one axis is obtained. This effect may be useful for the production of components where different specifications are needed in different parts of the component. An example of a potential application is an engine piston. In this paper it will also be shown how this technique would be very advantageous for the production of these structural components.