Semi-solid Casting Research Articles

Microstructural study for powder-chip reinforcement of similar matrix metal of AA6061 on semisolid cast by Solid-liquid mixed process

ABSTRACT Cavity formation during the solidification in the conventional casting process affects the cast properties and microstructure. This is generally reduced with help of semi-solid casting and several types of reinforcement particulates. Here, solid-liquid Mixed (SliM) casting process was used to investigate the effect of powder-chip-based reinforcements on the cast properties of 6061 Al alloy. In this study, machined chips of similar matrix metal was ball milled with a fine powder to make powder-chip reinforcement particles. Reinforcement particles of the AA6061 alloy was fed inside the melt of base metal to fabricate solid-liquid slurry under the protection of argon gas. Microstructural results confirm by a settlement of chip particulates inside the cavities and diffusion of powder particles. Also, it was found that a combined effect of 25 wt% reinforcement addition and 582°C pouring temperature extensively increase in the hardness and impact strength about 45.1% and 42.13%, respectively.

Unna boot efficacy in dermatologic diseases

To the Editor: The Paul Gerson Unna boot (UB) is a compressive semisolid gauze casting saturated with a mixture of zinc oxide, gum acacia, glycerol, castor oil, and deionized water.1 In the setting of stasis ulcers, UB compression results in wound granulation and reepithelization.2,3 Evidence supporting UB efficacy in other dermatologic conditions is scant.3,4 The purpose of this study is to review outcomes in 19 conditions treated with UB.

Localized Atmospheric Corrosion of Magnesium-Aluminum Alloys Produced by Semisolid Casting: A 2D and 3D Investigation

The localized corrosion of the two magnesium-aluminum alloys AM50 and AZ91 produced by a semisolid casting method was investigated under atmospheric corrosion conditions, in the presence of NaCl. Gravimetry confirmed the beneficial effect from ambient levels of carbon dioxide (CO2) in suppressing corrosion through the formation of magnesium hydroxy carbonates. Both 2D and 3D characterization revealed that ambient CO2 has a strong influence on the morphology and rate of localized corrosion. In CO2-free atmosphere, the alloys suffered localized corrosion resulting in clustered and interconnected cavities that extended deep into the material. In contrast, corrosion in the presence of ambient levels of CO2 (400 ppm) resulted in evenly distributed shallow corrosion sites. The results indicate that CO2 neutralizes the cathodic areas resulting in diminished cathodic activity and inhibiting NaCl(aq) droplet coalescence.

Feeding and Pore Formation in Semisolid Metal Casting

Semisolid casting can provide excellent castings, but the nature of the pore-forming mechanisms has not been properly clarified. In the current communication, it was suggested that hydrogen precipitated during slurry making might have a decisive role in the formation of both gas and shrinkage porosity. Intensive stirring at the end of the slurry making process may act as a degassing step. Without the intense shearing, structures of primary slurry particles form around the hydrogen pores, strongly affecting pore formation and feeding during the intensification stage.

Experimental Investigation and Optimization of the Semisolid Multicavity Squeeze Casting Process for Wrought Aluminum Alloy Scroll.

Scroll compressors are popularly applied in air-conditioning systems. The conventional fabrication process causes gas and shrinkage porosity in the scroll. In this paper, the electromagnetic stirring (EMS)-based semisolid multicavity squeeze casting (SMSC) process is proposed for effectively manufacturing wrought aluminum alloy scrolls. Insulation temperature, squeeze pressure, and the treatment of the micromorphology and mechanical properties of the scroll were investigated experimentally. It was found that reducing the insulation temperature can decrease the grain size, increase the shape factor, and improve mechanical properties. The minimum grain size was found as 111 ± 3 μm at the insulation temperature of 595 °C. The maximum tensile strength, yield strength, and hardness were observed as 386 ± 8 MPa, 228 ± 5 MPa, and 117 ± 5 HV, respectively, at the squeeze pressure of 100 MPa. The tensile strength and hardness of the scroll could be improved, and the elongation was reduced by the T6 heat treatment. The optimal process parameters are recommended at an insulation temperature in the range of 595–600 °C and a squeeze pressure of 100 MPa. Under the optimal process parameters, scroll casting was completely filled, and there was no obvious shrinkage defect observed inside. Its microstructure is composed of fine and spherical grains.

A Comparison Between Semisolid Casting Methods for Aluminium Alloys

Semisolid casting of aluminium alloys is growing. For magnesium alloys, Thixomoulding became the dominant process around the world. For aluminium processing, the situation is different as semisolid processing of aluminium is more technically challenging than for magnesium. Today three processes are leading the process implementation, The Gas-Induced Superheated-Slurry (GISS) method, the RheoMetal process and the Swirling Enthalpy Equilibration Device (SEED) process. These processes have all strengths and weaknesses and will fit a particular range of applications. The current paper aims at looking at the strengths and weaknesses of the processes to identify product types and niche applications for each process based on current applications and development directions taken for these processes.

Effects of process parameters on semi-solid squeeze casting performance of aluminum alloy scrolls for scroll compressors

The aluminum alloy scroll is one of the key parts of the scroll compressors widely used in the air-conditioning, refrigeration, and heat pump systems. In this work, the semi-solid squeeze casting (SSSC) process was used to fabricate the aluminum alloy scroll. The effects of process parameters including the pouring temperature, mold temperature, and squeezing velocity on the filling and solidification behaviors of the alloys were investigated through simulations based on the power law cut-off (PLCO) material model. Results show that there is a significant increase in the flow velocity of the slurry, and the area of the high-speed region enlarges with the increase of the pouring temperature. The homogeneity of the temperature and velocity fields in the slurry is improved with an increase in mold temperature. Both the filling time and its variation rate decrease with an increase in squeezing velocity. The maximum solidification time exhibits a linear variation with the increase in pouring temperature. The shrinkage area is decreased by increasing the mold temperature. The optimal process parameters of the SSSC process were obtained from simulation analysis, which are the pouring temperature of 595 °C, mold temperature of 350 °C, and squeezing velocity of 0.3 m·s−1. Moreover, the qualified scroll casting was fabricated using the SSSC process under the optimal process parameters.

The Combined Effect of Cooling Slope Plate Casting and Mold Vibration on Microstructure, Hardness and Wear Behavior of Al–Si Alloy (A390)

Semisolid casting using the cooling slope plate method (CSP) is known to refine the microstructure of hypereutectic aluminum alloys and enhance their mechanical properties. The current research investigates the combined effect of casting using the CSP and mechanical vibration of the mold on microstructure and wear behavior of A390 alloy. After pouring the alloy on the CSP, the mold (sand/metallic) was vibrated mechanically at 50 Hz during filling and up to solidification. Conventional casting with the same mold vibration conditions was also done for comparison. During CSP casting with mechanical vibration of the mold, the crystal nucleus multiplication inhibits the grain growth, and the dendrite break-up takes place simultaneously, leading to refinement of the microstructure. The double effect of the shear force by melt flow and vibrational turbulence is responsible for fragmentation of the particles. This finding was more pronounced in case of using the sand mold. The quantitative measurements showed that the size of primary Si reduced from ~ 184 μm for the conventional casting in the sand mold without vibration to ~ 70 μm when the mold was vibrated and from ~ 30 μm in case of CSP down to ~ 20 μm when CSP was followed by mechanical vibration of the mold. However, applying the mechanical vibration after CSP in case of the metallic mold increased the size of primary Si from ~ 21 to 36 μm. Accordingly, the improvement in the hardness and wear resistance of the CSP samples due to vibration was more significant in case of using the sand mold.

Influence of semisolid squeeze casting technology on alpha phase and eutectic of AlSi7Mg0.3

The paper deals with processing of material in semisolid state by the technology of semisolid squeeze casting. The investigated material was a subeutectic aluminium alloy AlSi7Mg0.3. The influence of various preparation meth-ods of batch material on the structure after processing by this technology was studied. Alloy AlSi7Mg0.3 was pre-pared as gravity cast, inoculated, heat treated and by technology of direct squeeze casting. In article is assessed microstructure of castings before and after processing by technology of semisolid squeeze casting. The shape and distribution of eutectic silicon was observed. The shape and the distribution of alpha phase formations has an im-pact on whether micro-volumes of molten eutectic will be closed in alpha phase or will be segregated along the boundaries of alpha phase formations. It was observed the partial inheritance in microstructure. Also the segrega-tion in surface layer was observed.

THE EFFECTS OF WELDING PRESSURE AND REINFORCEMENT RATIO ON WELDING STRENGTH IN DIFFUSION-BONDED AlMg3/SiCp COMPOSITES

In this study, using the diffusion welding method, welded joints were created with AlMg3/SiCp composite materials, and the mechanical strengths of these joints were examined. The AlMg3/SiCp composite specimens were cut out of plates produced directly with semi-solid stir-squeeze casting and contained 10% SiCp and 20% SiCp reinforcement. To examine the effects of reinforcement ratios on joint strength, specimen couples with the same and different reinforcement ratios were created. To examine the effects of different welding pressures on joint strength, by keeping the welding temperature constant at 580°C, welding was achieved under 3 different pressures as 1.5 MPa, 2.5 MPa and 3.5 MPa. By determining the mechanical strengths of the welded joints that were formed by shear test, the effects of reinforcement ratios and welding pressures on joint strength were investigated. As a result of the shear tests applied on the welded specimens, in the specimens that were diffusion-welded, welding quality decreased based on increasing reinforcement ratios, but as the amount of pressure and application duration increased, joint strength increased. As the SiC ratio increased in the joint zones, diffusion became difficult, and weak joints were occurred. The microscopic structure of the joint zone was examined by using optical microscopy and scanning electron microscopy (SEM) .It was seen that diffusion welding could be successfully performed in bonding SiCp-reinforced aluminum composites if the suitable welding pressure and duration are selected.

Optimizing the Pouring Temperature for Semisolid Casting of a Hypereutectic Al–Si Alloy Using the Cooling Slope Plate Method

This work investigates the optimum pouring temperature during semisolid casting (rheo-casting) of Al–17%Si alloy (A390) to obtain the best combination of microstructure modification and wear resistance. Pouring semisolid slurry was done in both metallic and sand molds to observe the effect of cooling rate on the optimum pouring temperature. The molten metal/slurry was poured into the specified mold type through a cooling slope plate which was continuously water cooled. Different pouring temperatures: 670, 690, 710 and 730 °C, were applied, and their influence on the microstructure and alloy properties was analyzed. Based on the obtained results, the optimum pouring temperature for semisolid casting was decided for the two mold types. Conventional casting was conducted at the optimum temperature in both metallic and sand molds for comparison. It was observed that rheo-casting using the cooling plate is an effective process in microstructure modification of A390 alloy in terms of refining and redistributing the primary Si and fragmenting the coarse AlFeMnSi phase. The optimum temperatures to obtain small particle size of primary Si, uniform distribution and regular shape using the cooling plate technique were 690 °C and 710 °C for the metallic and sand molds, respectively. This refinement and homogenization of the microstructure enhanced the hardness and wear resistance of alloy A390.

Semi-Solid Rheological Squeeze Casting Process of ZL114A Aluminum Alloy Thin-Wall Complex Casting

High-strength aluminum alloy with large-scale and thin-walled complex castings have broad application prospects in aerospace, weapons, electronics, defense and military industries. However, due to the uneven thickness of the plate, the casting defects are inevitable by the ordinary casting method, and it is impossible to accurately control the shape and performance of the casting in the casting process. Previous studies have found that the semi-solid rheological extrusion casting technology with short process and near-end type can help solve this technical problem. Therefore, this paper studies the semi-solid rheological extrusion casting process of thin-walled complex casting of ZL114A aluminum alloy. The combination of numerical simulation and experimental research is used to simulate and optimize the filling and solidification process of thin-walled specimens. Based on this, a semi-solid rheological extrusion casting test was conducted. The result showed that, (1) The optimized model can well reflect the filling and solidification process under different rheological extrusion casting parameters, and obtain defect-free castings through process optimization. (2) The thin-walled parts of the thin plate casting produced by semi-solid rheology extrusion have excellent mechanical property and ductility.

Effect of heat treatment on microstructure and properties of semi-solid squeeze casting AZ91D

Semi-solid AZ91D magnesium alloy billets were prepared by near-liquidus heat holding. Semi-solid squeeze casting was conducted at 575, 585 and 595 °C, respectively, with 1 mm·s−1 squeeze speed. The semisolid squeeze casting AZ91D samples were heat treated by T4 (solution at 415 °C for 24 h) and T6 (solution at 415 °C for 24 h + 220 °C for 8 h) processes, respectively. The microstructure and mechanical properties of the alloy in different states were investigated by means of OM, SEM and tensile testing machine. The results show that compared to as-cast alloy, the grain size of the semi-solid squeezed AZ91D decreased significantly, and with the increase of semi-solid squeeze temperature, the grain size of AZ91D increased. The grains of the alloy were refined by T4 treatment, and further refined by T6 treatment. T6 treatment greatly improved the tensile strength, elongation, and hardness, but did not significantly improve yield strength. After 575 °C squeeze casting and T6 treatment, the ultimate tensile strength (UTS) reached 285 MPa, the elongation reached 13.36%, and the hardness also reached the maximum (106.8 HV), but the yield strength (YS) was only 180 MPa. During the process of semi-solid squeeze casting and heat treatment, the matrix grain was refined and a large number of precipitated and secondary precipitated phases of Mg17Al12 appeared. Both the average size of matrix grain and secondary precipitated phase decreased, while the volume fraction of secondary precipitated phase increased. All these resulted in high tensile strength, elongation and hardness.

Fatigue Cycles and Performance Evaluation of Accelerating Aging Heat Treated Aluminum Semi Solid Materials Designed for Automotive Dynamic Components

The A357-type (Al-Si-Mg) aluminum semi solid casting materials are known for their excellent strength and good ductility, which make them materials of choice, preferable in the manufacturing of automotive dynamic mechanical components. Semi-solid casting is considered as an effective technique for the manufacturing of automotive mechanical dynamic components of superior quality performance and efficiency. The lower control arm in an automotive suspension system is the significant mechanical dynamic component responsible for linking the wheels of the vehicle to the chassis. A new trend is to manufacture this part from A357 aluminum alloy due to its lightweight, high specific strength, and better corrosion resistance than steel. This study proposes different designs of a suspension control arm developed, concerning its strength to weight ratio. Furthermore, this study aims to investigate the effect of accelerating thermal aging treatments on the fatigue life of bending fatigue specimens manufactured from alloy A357 using the Rheocasting semi-solid technology. The results revealed that the multiple aging cycles, of WC3, indicated superior fatigue life compared to standard thermal aging cycles. On the other hand, the proposed designs of automotive suspension control components showed higher strength-to-weight ratios, better stress distribution, and lower Von-Mises stresses compared to conventional designs.

Study on microstructure, mechanical and tribological properties of as-cast LPSO-containing Mg96Zn2Y2 matrix composite reinforced with TiB2 nanoparticles

In this work, the influence of TiB2 nanoparticles on microstructure, mechanical properties and tribological properties in the as-cast Mg96Zn2Y2 matrix composites containing 18R-LPSO (long-periodic stacking ordered) structure was investigated. Nano-TiB2/Mg96Zn2Y2 composites were fabricated by the combined process of powder mixtures compact extrusion and semi-solid stir casting. The results show that the appropriate TiB2 nanoparticles can significantly refine the microstructure, facilitate the precipitation of 18R-LPSO phase and optimize the growth pattern of 18R-LPSO and W phase. Meanwhile, the as-cast 1.5 wt%TiB2/Mg96Zn2Y2 composite with ultimate tensile strength (UTS) and elongation of 309 MPa and 16.2% exhibited better mechanical properties than that of matrix alloy with UTS and elongation of 175 MPa and 4.9%. In addition to traditional composites strengthening mechanisms, the synergistic strengthening effect (between TiB2 nanoparticles and 18R-LPSO phase) and the optimized growth pattern were also responsible for the excellent mechanical properties. Besides, the wear resistance of as-cast TiB2/Mg96Zn2Y2 composite is significantly improved under 5 N loading for 30 min, which was related to the enhanced hardness, work hardening ability and strength.

A study on the impact and fatigue failure of AZ91E–Ni coated alumina composites

ABSTRACT Failure analysis is a key concern in the development of composites. It not only helps to understand the material performance under severe loading conditions but also to decide the suitability of the material in particular applications. In this context, this paper highlights the behaviour of AZ91E with 2 wt-% nickel-coated alumina reinforced composites under different loading conditions. Composites were fabricated by semi-solid stir casting route while impact, and fatigue tests are conducted according to standard procedures. The properties of the prepared composite are discussed and compared with the monolithic alloy AZ91E. Ni coated alumina reinforced AZ91E magnesium-based composites yielded improved impact and fatigue strength because of good bonding between the matrix and reinforcement achieved through a metallic coating on the ceramic reinforcement. Further fractographical analysis is presented to understand the mechanism of failure.

Effect of Pouring Temperature on Mechanical Properties of Semisolid Cast A319 Aluminum Alloy

Semisolid metal (SSM) casting or thixoforming is a technique used to produce near net-shaped products. The process is used with non-ferrous metals, such as aluminium, copper and magnesium. Furthermore, it has advantage over conventional casting due to suppression of dendrite growth. In the present work, the semisolid casting of A319 aluminium alloy has been carried out by using an inclined plate with different melt pouring temperatures (620, 625, 630 and 635 °C). A319 alloy melt undergoes partial solidification when it flows down on an inclined plate. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed or fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. The prepared castings were checked for their mechanical properties like tensile, hardness and impact strength. The results obtained were compared with that of alloy prepared from conventional sand casting. It was found that there is an enhancement in mechanical properties due to shearing off columnar dendrites.

Evaluation of Fracture Mechanisms in Al-Si Metal Matrix Nanocomposites Produced by Three Methods of Gravity Sand Casting, Squeeze Casting and Compo Casting in Semi-Solid State

Magnetic stirring is considered to be the most useful stirring method in semi-solid casting processes which doesn’t have the restrictions of the mechanical stirring. In this research, fracture mechanisms of aluminum-Al2O3 nanocomposites produced by three methods of gravity sand casting, squeeze casting and compo casting in semi-solid state using electromagnetic stirring were studied and discussed. For this purpose, microstructure and fracture surfaces obtained from broken tensile test samples were analyzed using optical and scanning electron microscopies. On the fracture surfaces of all the samples, dimples were observed, which are the sign of ductile fracture. It was revealed that the dimples on the samples produced by the compo casting method are smaller, more spherical and uniformly distributed in the metal matrix in comparison with the ones from sand and squeeze casting. It also investigated that on the fracture surfaces of compo casting samples less cleavage planes, dendritic fracture and particles agglomeration were observed in comparison with the ones from the sand and squeeze casting processes.

Effects of T4 and T6 Heat Treatments on the Wear Behaviour of WC-Reinforced Mg Alloy Matrix Composite

Collective outcomes of WC particle reinforcement and heat treatment on the dry sliding wear rate of AZ91 magnesium metal matrix composite have been presented. The vacuum-assisted semi-solid stir casting method was employed to fabricate the composites. Wear study was conducted on the specimens using a pin-on-disc tribometer with EN8 steel as a counter material. The experiments were designed using Taguchi L27 array, with control factors viz. applied load (20, 40 and 60 N), sliding speed (1, 2 and 3 m/s), heat treatment (no treatment, T4 and T6) and WC wt% (0, 1.5 and 3). Energy-dispersive X-ray spectroscopy and scanning electron microscopy analyses were performed to study the surface of the tested specimens. T6-treated AZ91/3.0WC composite showed 63% enhanced resistance to wear due to the presence of β-phase (Mg17Al12) precipitation during the heat treatment process and WC reinforcements.

Simulation Fluidity Test for Semisolid Squeeze Casting

The paper deals with semi solid squeeze casting technology. Fluidity tests were designed for the selected technology. The shape of the test casting was designed in the shape of test bars with different thicknesses and also in the shape of a stepped casting. The thickness of the individual elements was chosen on the basis of a selected / preferred numbers R10 EN STN 17. As a result, the thickness of the elements was 2.0, 2.5, 3.15, 4.0, 5.0 and 6.3 mm. Designed fluidity tests were verified by using ProCast simulation software. The selected process parameters were: operating pressure 80 MPa, mold temperature 200 °C, piston speed 30 mm.s-1. The experimental material was an AlSi7Mg0.3 alloy with a different solid phase content. The initial solid amount were 50, 55 and 60 %. The effect of solidus and liquidus, temperature distribution and pressure was monitored during the evaluation of fluidity.