Ablation Casting Research Articles

Alloy development and process innovations for light metals casting

The combination of light metals (aluminum, magnesium and titanium) and innovative casting processes provides cost-effective technologies to produce lightweight components and systems for many industrial applications. This article provides a comprehensive and yet critical review of light alloy development for cast components used in lightweight and high-performance structural and propulsion applications. It also summarized some latest process innovations in gravity casting, high pressure die casting, and low pressure casting, to overcome some fundamental issues related to defect formation in casting processes. Emerging casting processes developed in the last twenty years, such as semisolid processing, squeeze casting, ablation casting, bimetallic overcasting, and diffusion solidification processing, are discussed for further development. Recent advances in casting simulation and the concept of Integrated Computational Materials Engineering (ICME) are summarized for casting applications. Finally, future perspectives in light alloy development (including green alloys, high entropy alloys and metal matric composites), process innovations (such as high integrity casting, multi-material manufacturing and additive manufacturing), and ICME development are presented to stimulate further research and sustainable development in this important field of metals processing technology.

Computer modelling of the ablation casting process and prediction of the strength properties of AC-42000 castings

Computer modelling of the ablation casting process and prediction of the strength properties of AC-42000 castings

The Influence of Various Matrixes on the Strength Properties of Moulding Sands with Thermally Hardened Hydrated Sodium Silicate for the Ablation Casting Process

The essence of ablation casting technology consists in pouring castings into single-use moulds made from the mixture of sand and a water-soluble binder. After pouring the mould with liquid metal yet while the casting is still solidifying, the mould destruction (washing out, erosion) takes place using a stream of cooling medium, which in this case is water. This paper focuses on the selection of moulding sands with hydrated sodium silicate for moulds used in ablation casting. The research is based on the use of water glass 145 and 150 as binders. As part of the research, loose moulding mixtures based on two silica sands from different sand mines with different content of binders were prepared. The review of literature data and the results of own studies have shown that moulding sand with hydrated sodium silicate hardened by dehydration is characterized by sufficient strength properties to be used in the ablation casting process. Our own research also confirmed the possibility of using these sand mixtures in terms of both casting surface quality and sand reclamation. The results presented in this paper prove that both sand grains and types of binder tested may be used as components in moulding sands devoted to ablation casting.

Features of A356 alloy solidified under water cooling conditions

This study focused on using a simple quench method to study the effect of ablation water cooling on microstructural features and heat treatment response of A356 alloy. Molten alloy of a given quantity was solidified in water and the resultant microstructure was characterized and compared with that solidified in metal molds and that reported on ablation castings. It is found that the simple method is suitable in simulating certain features of eutectic solidification during ablation casting. The microstructural length scales obtained in this multicomponent alloy are comparable to that predicted by theories developed for binary alloys. The heat treatment response of the water cooled samples are much faster than that of conventional castings which can be translated into reduced energy consumptions and significant cost savings if the heat treating process is optimized for ablation casting.

Modeling Ablation Casting

Research published in open literature on ablation casting has been mainly experimental. Modeling of this innovative technology is scarce. This article describes an initial attempt in modeling ablation casting process. Material properties and boundary conditions were defined for calculating cooling curves and microstructural length scales in A356 alloy castings made using sand casting and ablation casting processes. Model predictions were compared with published data on cooling curves and solidification times in an A356 alloy casting. The validated model was then used to predict unique solidification features associated with the ablation casting process, including the eutectic solidification time, shrinkage porosity formation, eutectic front morphology, the advancing rates of the eutectic front and the associated eutectic silicon morphology. Simulation results indicate that the progressive advancing ablation cooling is capable of reducing secondary dendrite arm spacing, modifying the eutectic silicon phase owing to the water quench effect, and eliminating shrinkage porosity using much smaller risers than usual if the ablation is correctly driven towards the risers.

The Influence of Inorganic Binder Type on Properties of Self-Hardening Moulding Sands Intended for the Ablation Casting Process

The aim of the present work is to compare the properties of self-hardening moulding sands based on inorganic binders based on sodium silicate of different modules, geopolymer binders and phosphate binders and to prove they can be used in the ablation casting process. Ablation casting is a process in which, directly after pouring the liquid alloy, the mould is sprayed with water until it is completely eroded and a finished, cooled casting is obtained. The use of proecological water-dilutable binder makes it possible to recover the sand matrix after drying the suspension that remains after the process. Moulding sands were prepared on the basis of four inorganic binders available on the market. For each of the moulding sands the bending strength was tested after 1, 2, 4 and 24 h of hardening. Then, the masses with optimum bending strength were selected and subjected to gas emissivity tests. A thermal analysis of moulding sands selected for testing was also carried out in order to determine the loss of mass during annealing. The susceptibility of moulds to erosion under the influence of ablative medium was also assessed by measuring the time of mould erosion. Tests showed the possibility of using self-hardening moulding sands based on inorganic binders for the ablation casting process of aluminium-silicon alloys.

Ablation Casting of Thin-Wall Ductile Iron

An unalloyed thin-wall ductile cast iron with the chemical composition of C = 3%, Si = 4.15%, Mn = 0.36%, Mg = 0.04%, and carbon equivalent of 4.39% was cast by both conventional and ablation casting in sections of nominal thickness 1, 2, 4, 8 mm. The effect of various commercial inoculants (based on Zr, Sr, and Ba) on microstructure and mechanical properties of the samples was investigated. In the ablation casting, the mold is eroded away by water, and the water becomes responsible for the heat transfer from the casting. In our work, ablative cooling could not be applied quickly enough to have any influence on the microstructure of the 1 mm thick cast section. In the 2-mm-thick specimen, ablation increased the nodule count from 497 to 1484 and graphite nodularity from 76 to 93%. In the 8 mm section, the tensile yield strength increased from 539 to 624 MPa and elongation was increased from 4.9 to 10.2%.

Effect of Cooling Rate on the Microstructure and Mechanical Properties of High-Zinc AA 5182 Aluminum Wrought Alloy Cast by the Ablation Green Sand Mold Casting Process

In this research, the effects of cooling rate on the microstructure and mechanical properties of 5182 aluminum alloy were investigated. Two plates were cast using conventional and ablation green sand mold casting processes and microstructure, casting defects, tensile properties, and hardness of these two castings were compared to each other. In the ablation casting, water spraying onto the mold was started immediately after filling the mold. In the ablation casting compared to the conventional casting following results were obtained: SDAS decreased from 70 to 41 µm. The eutectic phases were modified from coarse and lamellar morphology to fine and divorced morphology. The porosity content decreased significantly from 9.3 to 1.8%. The yield and ultimate tensile strengths increased from 153 and 188 MPa to 163 and 259 MPa, respectively, while the elongation increased from 2.3 to 12% and the hardness remains unaffected.

Ablation Casting: Solidification Characteristics, Microstructure Formation, and Mechanical Properties

Ablation casting is an emerging sand casting technology that achieves high cooling rates in a casting during its solidification, especially its eutectic solidification of the metal, resulting in an extremely fine eutectic microstructure, reduced levels of defect, and enhanced mechanical properties of the casting. The technology is creating extensive interest in the industry for its capability in producing castings with high mechanical properties and internal integrity. However, scientific research lags behind the industrial applications of this new technology. There is a lack of scientific understanding on the solidification features of the castings made using ablation casting. Experimental data on the microstructural length scales seem inconsistent. This article aims at interpreting the experimental data available in the literature by considering the solidification characteristics of ablation casting. The paper also discusses certain research needs to further exploring the potential of the ablation casting process.

High-Performance Al/PDMS TENG with Novel Complex Morphology of Two-Height Microneedles Array for High-Sensitivity Force-Sensor and Self-Powered Application.

Triboelectric nanogenerators (TENGs) are widely applied to self-powered devices and force sensors. TENGs consist of the electrode-layer frequently made of high-cost conductors (Ag, Au, ITO) and the tribo-layer of rigid negative-triboelectricity fluoropolymers (PTFE, FEP). The surface morpholoy is studied for enhancing performance. Here, a high-performance Al/PDMS-TENG is proposed with a complex morphology of overlapped deep two-height microneedles (OL-DTH-MN) fabricated by the integrated process of low-cost CO2 laser ablation and PDMS casting for self-powered devices and high-sensitivity force/pressure sensors. The high open-circuit voltage and short-circuit current of the OL-DTH-MN-TENG are 167 V and 129.3 µA. Also, the sensitivity of the force/pressure sensor of the OL-DTH-MN-TENG is very high, 1.03 V N-1 and about 3.11 V kPa-1 , at an area of 30 cm2 that is much higher than the sensitivity of about 0.18-0.414 V N-1 and 0.013-0.29 V kPa-1 of conventional TENG sensors. Meanwhile, the high-performance OL-DTH-MN-TENG not only exhibits the energy storage capability of charging a 0.1 µF capacitor to 2.75 V at 1.19 s, to maximum 3.22 V, but also activates various self-powered devices including lighting colorful 226 LEDs connected in series, the "2020-ME-NCKU" advertising board, a calculator and a temperature sensor. Numerical simulation is also performed to support the experiments.

Structure and Properties of Carbon Steel Cast by the Ablation Process

Ablation casting is a relatively new casting technique which can improve the mechanical properties of castings. In this paper, the microstructure and mechanical properties of plain carbon steel castings produced by conventional casting and ablation casting techniques were compared. It was found that ablation increased the ultimate strength from 638 to 1094 MPa and tensile elongation increased from approximately 13 to 16% as a result of severe microstructural changes from ferrite and pearlite to acicular ferrite, bainite, and martensite. Ablation increased the core hardness of the casting from 182 to 467 HB and the surface hardness from 205 to 508 HB.

A Preliminary Study Upon the Applicability of the Direct Water Cooling with the Lost Foam Casting Process

Direct water cooling (DWC) application with the lost foam casting (LFC) process was inspired by the ablation casting technique. Ablation casting is designed to combine the controlled filling property of sand mold casting and the rapid cooling of the high-pressure die casting. Briefly, in this method, sand casting is followed by the removal of the mold by water spray and cooling of the part within a short time. The use of special water-soluble inorganic binders facilitates the mold breakdown. However, due to no use of binder materials in the LFC method, the DWC process may become more effective. In this study, similar cooling techniques were applied to the lost foam castings of A356 alloy by two techniques. In the first one, cooling was achieved by tipping the mold content over into a container with a sufficient amount of water after the casting process. The second process was carried out by pouring a sufficient amount of water onto the mold following the casting process. These two developed methods were named as “quench casting” and “splash casting,” respectively. It was seen that both methods changed the traditional casting microstructure and properties considerably. A serious decrement in secondary dendritic arm spacing with accompanying modification of the eutectic silicon was observed for the specimens produced via both methods. Hardness values increased significantly, and the results indicate that splash casting is preferable than quench casting because it exhibits better and more stable properties.

High contact surface area enhanced Al/PDMS triboelectric nanogenerator using novel overlapped microneedle arrays and its application to lighting and self-powered devices

One key to enhance the output performance of triboelectric nanogenerators (TENG) is how to increase the effective contact area that strongly depends on the feature morphology and pattern density. Conventional morphologies of TENG including pyramids, cubes, lines, pillars, and domes with insufficient feature surface area are generally fabricated using an expensive-and-time-consuming lithography and etching process. Here, we propose a novel morphology of overlapped microneedles (OL-MN) arrays for high total contact surface area to enhance the output performance of aluminium/polydimethylsiloxane (Al/PDMS) TENG under low operation frequencies using hand tapping. Two kinds of separate low-density and high-density microneedles arrays, namely LD-MN and HD-MN, are comparatively studied. The integrated process of low-cost CO2 laser ablation and PDMS casting is used for rapid prototyping. The OL-MN has the highest total contact surface area compared to the LD-MN and HD-MN at the constant laser power and scanning speed. The output performance of open-circuit voltage (Voc) and short-circuit current (Isc) of OL-MN-TENG are 123 V and 109.7 μA those are 3.66 and 3.71 times the Voc and Isc of LD-MN-TENG, respectively. The excellent OL-MN-TENG can light on 103 LEDs connected in series and store energy in capacitors for application to various self-powered devices.

Selection of hardening technology of moulding sand with hydrated sodium silicate binder devoted to aluminum alloys ablation casting

Selection of hardening technology of moulding sand with hydrated sodium silicate binder devoted to aluminum alloys ablation casting

Rapid prototyping of biodegradable microneedle arrays by integrating CO2 laser processing and polymer molding

An integrated technology of CO2 laser processing and polymer molding has been demonstrated for the rapid prototyping of biodegradable poly-lactic-co-glycolic acid (PLGA) microneedle arrays. Rapid and low-cost CO2 laser processing was used for the fabrication of a high-aspect-ratio microneedle master mold instead of conventional time-consuming and expensive photolithography and etching processes. It is crucial to use flexible polydimethylsiloxane (PDMS) to detach PLGA. However, the direct CO2 laser-ablated PDMS could generate poor surfaces with bulges, scorches, re-solidification and shrinkage. Here, we have combined the polymethyl methacrylate (PMMA) ablation and two-step PDMS casting process to form a PDMS female microneedle mold to eliminate the problem of direct ablation. A self-assembled monolayer polyethylene glycol was coated to prevent stiction between the two PDMS layers during the peeling-off step in the PDMS-to-PDMS replication. Then the PLGA microneedle array was successfully released by bending the second-cast PDMS mold with flexibility and hydrophobic property. The depth of the polymer microneedles can range from hundreds of micrometers to millimeters. It is linked to the PMMA pattern profile and can be adjusted by CO2 laser power and scanning speed. The proposed integration process is maskless, simple and low-cost for rapid prototyping with a reusable mold.

The effect of waterjet beginning time on the microstructure and mechanical properties of A356 aluminum alloy during the ablation casting process

The effect of delay time (time interval between melt pouring and waterjet beginning) achieved by ablation process on the microstructure and mechanical properties of A356 aluminum alloy is investigated. By applying the process of ablation cooling 0.5min after melt pouring, eutectic silicon and iron intermetallic size were reduced extremely and the dendrite arm spacing was refined almost considerably. For 0.5min and 1min of delay times ablated samples, besides interdendritic phases size reduction, the morphology of eutectic silicon was converted from coarse needle-like particles to fine and fibrous morphology. Also gas and shrinkage porosities were minimized considerably without any melt treatment. The mechanical properties of 0.5min ablated samples were improved significantly and in comparison with the conventional casting samples in the sand mold, the ultimate tensile strength and elongation were increased from 161MPa to 264.5MPa and from 3% to 12% respectively. Fractography investigations showed a ductile fracture surface for ablated samples.

The Research on the Ablation Casting Technology for Aluminium Alloys

The article presents preliminary results of the research on the ablation casting technology. The guidelines for the designing of an equipment to carry out the process were described. Based on the above-mentioned instructions a test stand was developed and built. Many tests were performed concerning the influence of the water jet directed at a sand mould on its removal tendency. The effect of the cooling rate of a tested cast parts on its microstructure was studied based on metallographic and radiographic examinations.

Magnesium casting technology for structural applications

This paper summarizes the melting and casting processes for magnesium alloys. It also reviews the historical development of magnesium castings and their structural uses in the western world since 1921 when Dow began producing magnesium pistons. Magnesium casting technology was well developed during and after World War II, both in gravity sand and permanent mold casting as well as high-pressure die casting, for aerospace, defense and automotive applications. In the last 20 years, most of the development has been focused on thin-wall die casting applications in the automotive industry, taking advantages of the excellent castability of modern magnesium alloys. Recently, the continued expansion of magnesium casting applications into automotive, defense, aerospace, electronics and power tools has led to the diversification of casting processes into vacuum die casting, low-pressure die casting, squeeze casting, lost foam casting, ablation casting as well as semi-solid casting. This paper will also review the historical, current and potential structural use of magnesium with a focus on automotive applications. The technical challenges of magnesium structural applications are also discussed. Increasing worldwide energy demand, environment protection and government regulations will stimulate more applications of lightweight magnesium castings in the next few decades. The development of use of Integrated Computational Materials Engineering (ICME) tools will accelerate the applications of magnesium castings in structural applications.

Effect of ablation casting on microstructure and casting properties of A356 aluminium casting alloy

Recently the Ablation Casting Technology was invented as a new casting process to improve foundry products quality. In this study, the effects of processing variables on the porosity content, microstructure and feedability of A356 casting alloy were investigated. Secondary dendrite arm spacing (SDAS) and eutectic silicon morphologies were studied to evaluate the influence of Ablation Casting on the microstructure. Casting density was measured in order to identify porosity content and feedability of ablated and non-ablated specimens. In addition, solidification behavior of the samples was investigated by using thermal analysis technique. The cooling curves and the first derivative curves were plotted and compared with each other. Results showed the ablation process could increase solidification rate significantly. In addition, the microstructural evidences revealed that Ablation Casting process results in more fine and homogeneous structure compared to the nonablated casting. The feedability improved, SDAS reduced to 35% and porosity content decreased to 3.84 vol.% by implementing this process. It concluded the Ablation Casting is an effective process to gain higher quality in aluminum foundry.

Fatigue life of ablation-cast 6061-T6 components

The fatigue life of 6061-T6 alloy, normally used in its wrought form, was investigated in this study in cast form from parts produced by the new ablation casting process. All specimens were excised from military castings. Unidirectional tensile test results yielded elongation values comparable to forgings and extrusions. A total of 39 fatigue specimens were tested by the rotating cantilever beam technique at five maximum stress levels. Moreover nine specimens excised from a forging were also tested for comparison. Results revealed that the fatigue life of ablation-cast 6061-T6 (i) follows a three-parameter Weibull distribution, and (ii) is comparable to data from the 6061 forging and is superior to conventionally cast Al-7% Si–Mg alloy castings published in the literature. Analysis of the fracture surfaces of ablation-cast 6061-T6 via scanning electron microscopy showed the existence of fracture surface facets and multiple cracks propagating in different directions.