Cast Alloy Research Articles

Microstructure and properties of the GEWZ522K casting magnesium alloy based on the Mg–Gd–Nd–Y–Zn–Zr system

The article discusses the solidification and phase composition of the (wt.%) Mg–4.8Gd–2.1Nd–1.6Y–0.4Zn–0.6Zr (GEWZ522K) casting alloy. It is demonstrated that in the as-cast state, the alloy structure comprises primary zirconium particles, dendrites of the magnesium solid solution (αMg), and eutectic intermetallic phases located between dendritic branches. Following solution heat treatment at t = 530±5 °C, the alloy transitions into a single-phase state and can be significantly strengthened through artificial aging after quenching. It is recommended to apply alloy aging at t = 250 °C for 8–10 h or at t = 200 °C for 15–18 h. This approach leads to the maximum strengthening of the alloy, with the best mechanical properties achieved for the alloy aged at t = 250 °C. Regardless of the aging method used, the ultimate tensile strength (UTS) of the samples surpasses 300 MPa, which significantly exceeds that of commercial casting alloys according to GOST 2856-79. The measured corrosion rate for the GEWZ522K alloy is 7.5±0.4 mm/year, that slightly higher than that for the less alloyed commercial alloy ML10 (approximately 2.5 mm/year) tested under similar conditions. Furthermore, the alloy was subjected to tests for ignition resistance when in contact with air. It was observed that with continuous airflow over the specimen’s surface, ignition centers appear at t = 625 °C due to the breakdown of the oxide film, causing the alloy to nearly completely melt. Therefore, the GEWZ522K alloy can be employed as a high-strength casting alloy. However, during the operation of cast parts, particular attention must be paid to safeguarding the surface of these parts against corrosion.

The Effect of Recasting on Microhardness of Cobalt/Chromium Base Metal Alloys

Castings made of base metals include the cobalt/chromium alloy. This alloy is frequently used in dentistry to make crowns, bridges, and partial dentures. This alloy was first promoted as a less expensive option to cast gold that had even better physical and mechanical properties and approximately comparable bioco mpatibility. It was better suited for long-span bridges and cast prostheses. Aim: to assess how recasting affects the cobalt/chromium base metal alloys' microhardness. Material and Methods: 42 disc-shaped specimens of cobalt/chrome alloy measuring 5 mm in diameter and 3 mm in thickness were prepared. The cast specimens were divi ded into three groups based on the weight of the newly and pr eviously cast Co/Cr alloy addition: the first group was 14 specimens of (new cast) alloy; the second group was 14 specimens of (50% new cast+50% old cast) alloy; and the third group was 14 specimens of (old cast) alloy. All the speci mens were subjected to measuring the microhardness prope rty by using a digital microhardness tester. Results: Using a student t-test, it was determined that there was no significant difference in the microhardness between the two gr oups (new cast) and (new cast + old cast), and that there was al so no significant difference between the groups (new cast + ol d cast) and (old cast) (P-value p>0.05), yet that there was a highly significant difference between the two groups (new cast) and (old cast) (P-value P<0.01). Conclusion: The incl usion of different ratios of fresh and recast Co/Cr alloys can affect the microhardness. Also, the recast Co/Cr metal alloy has shown excellent results for microhardness property.

Effect of Alloying Elements on the Short-Range Orders and Atomic Diffusion Behavior of Liquid Al-9Si Cast Alloys.

To investigate the influence of alloying elements (Zn, Mg, and Cu) on the structural and dynamical properties of liquid Al-9Si alloy, we conducted ab initio molecular dynamics (AIMD) simulations. Our results indicate that the structure of Al-Si-M ternary alloys is determined with a combination of atomic radii and mixing enthalpy, while the dynamic properties are primarily influenced by electronic structure of the alloying elements. Specifically, the addition of Cu promotes the formation of Al-Cu short-range order (SRO), while Zn has a higher propensity for Zn-Zn SRO. The Al-Cu SRO in liquid alloy may serve as the precursor for the Al2Cu reinforcing phase in Al-Si-Cu alloys. Upon the addition of Mg, a greater number of relatively stable perfect and distorted icosahedral structures, as well as hcp and bcc ordered structures with lower energies, are observed. Additionally, the presence of Mg leads to a reduction in the atomic diffusion rates of Al and Si, while Cu and Zn exhibit complex diffusion behavior influenced by the presence of Si atoms.

The novel strategy for enhancing mechanical properties and corrosion resistance via regulating multi-scale microstructure characteristics in Al-Si-Cu-Mg-Zr cast alloy

High strength and low corrosion resistance are always the contradiction in Al-Si-Cu-Mg cast alloy due to introducing high Cu and Mg levels. In this work, the new strategy was achieved for enhancing corrosion resistance and mechanical properties by regulating multi-scale microstructure characteristics in Al-9Si-4.2Cu-0.25Mg-Zr alloy. Electrochemical and corrosion morphology results indicate that the addition of Zr significantly enhances the corrosion resistance of the alloy. The grain refinement inhibits the charge transfer process between cathode phases and the matrix is the main reason at the Zr level of less than 0.15%. When the Zr level is up to 0.3%, the multi-scale synergistic effect of grain refinement and passive film enhancement significantly inhibits the corrosion process. Moreover, 0.3%Zr addition increases the yield strength to 419 MPa, tensile strength to 490 MPa, and the acceptable fracture elongation to 3.8%. The strengthening of mechanical and corrosion properties originates from the nano-Al3Zr precipitates after T6 treatment. This study provides a novel micro-mechanism and design strategy for simultaneously improving corrosion resistance and enhancing the mechanical properties of Al-Si-Cu-Mg cast alloy.

Universal Model for the Quality Analysis of Aluminium Alloys Castings

Universal Model for the Quality Analysis of Aluminium Alloys Castings

Electrochemical corrosion behavior of Mg-Al-Sn alloys with different morphologies of β-Mg17Al12 phase as the anodes for Mg-air batteries

The morphologies of β-Mg17Al12 phase in Mg-Al-Sn alloys are tailored by using different molds during the casting of liquid alloys. The electrochemical corrosion behavior of these alloys is investigated; the results indicate that the finer β-Mg17Al12 induced by a thick-walled copper mold facilitates the spalling of oxidation products and mitigates the self-corrosion during galvanostatic discharge. All these features lead to the superior anode performance when used for Mg-air batteries, as compared with the coarser β-Mg17Al12 prepared via a flat iron mold. Furthermore, the intrinsic linkage between electrochemical corrosion behavior and β-Mg17Al12 morphologies in Mg-Al-Sn specimens is unraveled according to electrochemical response and microstructural characterization.

Third-generation biodegradable bone implants: A novel Mg-1Zn-0.5Sc alloy treated by laser shock peening to improve its characteristics

Magnesium (Mg) and its alloys are of much interest as promising third-generation bio-materials for bone implant applications; however, challenges remain for the alloy's mechanical integrity and bio-corrosion behaviour. Therefore, appropriate alloying elements and surface-modification techniques are required to overcome these limitations. Zinc and scandium were found to possess good biocompatibility and biodegradability, in addition to magnesium. This study aims to enhance the mechanical integrity and bio-corrosion resistance behaviour of a novel Mg-1wt% Zn-0.5wt% Sc cast alloy by laser shock peening surface treatment with multiple passes (LSP-2 pass and LSP-3 pass). The microstructural and texture evolution was investigated using various techniques, including field emission scanning electron microscopy with energy-dispersive spectroscopy (FESEM-EDS), optical microscopy (OM), X-ray diffraction (XRD) analysis, electron back-scattered diffraction analysis (EBSD), as well as the surface residual stress, wettability, microhardness, tensile strength, electrochemical polarization test, and biocompatibility were analysed on as-cast, LSP-2 pass and LSP-3 pass specimens. LSP induced beneficial compressive residual stress around the surface and sub-surface region of Mg-1Zn-0.5Sc alloy due to severe plastic deformation, which led to grain refinement through the twinning mechanism of the Mg alloy. Also, the dispersion of second-phase particles (β-ScZn) was observed while analysing the XRD profiles. Strain hardening, grain refinement, and precipitate strengthening have contributed to the structure and texture evolution, which enhanced the microhardness, tensile strength, ductility, and corrosion resistance of the Mg-1Zn-0.5Sc alloy. From in vitro studies, a low rate of corrosion in simulated body fluid and less cytotoxic behaviour were observed for the LSP-3 pass Mg-1Zn-0.5Sc alloy.

IMPROVING THE STRENGTH AND CORROSION PROPERTIES OF ALUMINIUM ALLOYS WHEN MODIFICATION WITH NANODISPERSED COMPOSITIONS

Aluminium alloys of the Al-Si and Al-Mg-Sc systems, which are promising for nuclear power generating facilities, were studied. The AK9 aluminium casting alloy and the 1545 wrought alloy were selected as the study materials. Modification of aluminium alloys with a multicomponent nanodispersed modifier based on Mg2Si and SiC was proposed. Grain grinding of modifying alloys by 1.5–2 times, strength properties increasing by 12…18% and corrosion resistance improving were achieved. The mechanism of action of the multicomponent nanodispersed modifier in an aluminium melt was proposed. The use of such modifiers facilitates the technological process, is environmentally safe, and leads to a uniform distribution of the introduced nanocompositions, which increases the strength and stability of alloys. The results achieved showed the effectiveness of modification aluminium alloys with nanodispersed compositions.

Differences in Oxidation Behavior of Conventionally Cast and Additively Manufactured Co-Base Alloy MAR-M-509

AbstractHigh-temperature oxidation behavior of conventionally cast and additively manufactured (AM) Co-base alloy MAR-M-509 was compared in the present study. The specimens were exposed in air at 1000 °C and characterized by means of scanning electron microscopy equipped with energy/wavelength dispersive x-ray spectroscopy (EDX/WDX) and electron backscatter diffraction as well as transmission electron microscopy. Substantial differences in the oxidation processes of two alloy versions were observed. Faster oxidation of the cast alloy was mainly induced by (1) oxidation of coarse primary carbides, (2) internal oxidation and nitridation processes and (3) incorporation of other alloy constituents (e.g., Co, Ni, W) into the Cr-oxide scale. AM specimens, in contrast, formed a more homogeneous, thinner and better adherent external oxide scale. The results are discussed in terms of differences in the chemical composition and alloy microstructure, including the grain size distribution in the material and the morphology of the strengthening precipitate phases.

The Casting and Hot Forging of Low-Carbon Copper-Bearing Steel and Its Substructural Characterization

The casting of metal alloys followed by hot forging is a widely used manufacturing technology to produce a homogeneous microstructure. The combination of mechanical and thermal energy envisages the microstructural properties of metal alloys. In the present investigation, a metal alloy of composition 0.05C-1.52Cu-1.51Mn (in weight %) was cast in an induction furnace using a zirconia crucible. The melt pool was monitored using optical emission spectroscopy (OES) to maintain the desired composition. The as-cast block was then subjected to forging under a pneumatic hammer of 0.5 t capacity so that any casting defects were eliminated. The as-cast block was reheated to a temperature of 1050 °C and held at that temperature for 6 h to homogenize, followed by hammering with a 50% strain using a pneumatic hammer. The microhardness was calculated using a Vickers microhardness testing apparatus. The microstructure characterization of the processed alloy was carried out using an optical microscope, electron backscattered diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDXA), and a transmission electron microscope (TEM). The sample for optical microscopy was cut using a diamond cutter grinding machine and surface polishing was carried out using emery paper. Further, mechanical polishing was performed to prepare the samples for EBSD using a TEGRAPOL polishing machine. The EBSD apparatus was operated at a 20 kV accelerating voltage, 25 mm from the gun, and with a 60 µ aperture size. HKL Technology Channel 5 Software was used for the post-processing of EBSD maps. The procedure of standard polishing for OES and TEM sample preparation was followed. Recrystallization envisages equiaxed grain formation in hot forging; hence, the strain-free grains were observed in the strained matrix. The lower distribution of recrystallized grains indicated that the driving force for recrystallization was not abundant enough to generate a fully recrystallized microstructure. The fractional distribution of the misorientation angle between 15 and 60° confirms the formation of grain boundaries (having a misorientation angle greater than 15°) and dislocations/subgrain/substructures (having a misorientation angle less than 15°). The fraction of misorientation angle distribution was higher between the angles 0.5 and 6.5°; afterwards, it decreased for higher angles. The substructure was observed in the vicinity of grain boundaries. The softening process released certain strains, but still, the dislocation was observed to be deposited mostly in the vicinity of grain boundaries and at the grain interior. The fine precipitates of the microalloying element copper were observed in the range of size in nanometers. However, the densities of these precipitates were limited and most of these precipitates were deposited at the grain interior. The microhardness of 210.8 Hv and mean subgrain size of 1.61 µ were observed the enhanced microhardness was due to the limited recrystallized grains and accumulation of dislocations/subgrain/substructures.

Study on chemical corrosion properties of titanium alloy in 2A14 aluminum melt

Titanium alloy radiation rods have excellent physical and chemical properties compared to other materials, and are commonly used for ultrasonic casting of 2A14 aluminum alloy. However, titanium alloys are chemically corroded in high-temperature aluminum melts for a long time, making it difficult to precisely regulate the elemental composition during casting. In order to better understand the high-temperature chemical corrosion mechanism of titanium alloy radiation rods, this research looks into the corrosion morphology, weight loss, surface roughness, and reaction layer. The study’s findings suggest that the rate of chemical corrosion of titanium alloy in high-temperature aluminum melt is often inversely correlated with the degree of roughness, with the degree of roughness changing nonlinearly during the corrosion process. Titanium alloy weight loss rates with roughness Ra0.4 μm, Ra7.2 μm, Ra9.5 μm and Ra9.8 μm are 0.16 mg per min, 0.25 mg per min, 0.37 mg per min and 0.29 mg per min, respectively. The corrosion product of the chemical corrosion process is TiAl3, which is granular. Under varying roughness conditions, the solid-liquid interface of Al/Ti emerges reactants after 4 min, and the TiAl3 reaction layer arises after 12 min. Furthermore, the reaction layer with little roughness is flat and compact, whereas the reaction layer with great roughness is loose and contains many faults. At the same time, the growth rate of the reaction layer decreases slightly. And the greater the surface roughness, the greater the TiAl3 reaction layer grows at the titanium alloy matrix.

Tribological Behavior of Cast Aluminum Matrix Composites After Multiple Remelting

One of the limiting factors for expanding the applications of aluminum alloy castings in many high-tech industries is the insufficient level of tribological properties, especially under conditions of dry and abrasive wear. Reinforcing of aluminum alloys with hard ceramic particles, i.e., transition to aluminum matrix composites, allows significantly increasing their resistance against dry sliding friction, scuffing, and seizure in wide temperature and force intervals of operation. Among the numerous problems related to the industrial implementation of cast aluminum matrix composites, the problem of their recycling takes the important place. This work is aimed at establishing the influence of metallurgical processes during remelting on the change in tribological properties of cast Al-Si-B4C aluminum matrix composites. For this purpose, tribological tests in conditions of dry friction according to the ball-on-disc scheme were used. Reinforcing of an AlSi12 matrix alloy with B4C particles leads to a decrease in the composite friction coefficient and the mass wear in the as-cast state in comparison with an unreinforced matrix alloy. During remelting, the tribological properties of the aluminum matrix composites do not deteriorate. Repeated remelting leads to the improvement in particle distribution uniformity, formation of the Al3BC phase at the matrix/particle interfaces, fragmentation of reinforcing B4C particles due to cyclic thermal loads as well as an increase in the porosity fraction. The changes in the structural-phase composition during remelting have a direct influence on the level of tribological properties. Typical effects associated with dry friction, such as plastic deformation of the matrix material and the formation of areas of adhesion-cohesive fracture, indicative of scuffing, were revealed by SEM analysis of the wear tracks of an unreinforced matrix alloy. For the composite material, these effects manifested to a much lesser extent. A qualitatively similar sliding wear behavior was observed for all composite samples, regardless of the remelting iteration. The study suggests that the formation of a transitional tribolayer may occur during dry sliding friction of aluminum matrix composites, which can reduce the friction coefficient.

Electrochemical corrosion of stir cast and heat-treated magnesium alloy EV31A in different electrolytes: Analysis via X-ray photoelectron spectroscopy

The study aims to determine the chemical state of elements in EV31A after electrochemically corroded in four different electrolytic solutions. EV31A, a magnesium alloy containing rare earth elements, was manufactured via stir-casting and heat-treated based on T4 and T6 conditions. Electrochemical corrosion of the as-cast, T4, and T6 EV31A were carried out in 0.6 M NaCl, 0.05 M H2SO4, 0.1 M HNO3, and 0.1 M HF solutions. In addition, the X-ray photoelectron spectroscopy (XPS) examination was performed on the corroded surface of EV31A. During the XPS analysis, the elements such as Magnesium (Mg), Neodymium (Nd), Gadolinium (Gd), Zinc (Zn), Zirconium (Zr), chlorine (Cl), sulphur (S), nitrite (N), fluorine (F), and oxygen (O) were studied, and only the peaks of Mg, O, Nd, and Gd were detected on the surface of corroded alloy. In all test settings, the corrosion resistance of the as-cast alloy is better than that of the heat-treated alloy. Even though the corrosion resistance of the as-cast alloy is high, its corrosion rate of EV31A in H2SO4 and HNO3 is very high. The corrosion resistance of as-cast EV31A in NaCl and HF mainly results from the formation of Nd2O3 and electronegative fluorine, respectively, as determined by XPS.

Investigation of chemical short range order strengthening in a model Fe–12Ni–18Cr (at. %) stainless steel alloy: A modeling and experimental study

Solid solution strengthening remains the basis for many industrial alloys, yet chemical short-range order (CSRO) can also play a significant role in the strengthening of alloys with appreciable alloying additions, such as in Austenitic stainless steels. In this work, we study the evolution of CSRO under various annealing temperatures and its role on the mechanical strength of a ternary Fe–12Ni–18Cr (at.%) alloy using molecular dynamics (MD) and Monte Carlo atomistic simulations and experimental measurements from mechanical microindentation and atom-probe tomography (APT). A general model that incorporates the role of CSRO into a solute–solution strengthening model is proposed, based on a family of analytical models due to Varvenne et al. (2016) which takes into account dislocation-solute misfit interaction, and a more recent extension due to Nag and Curtin (2020) which incorporates the role of solute–solute interactions during dislocation slip. Predictions of the modified model are validated against MD shearing simulations using two commonly used embedded atom model (EAM) interatomic potentials for Austenitic stainless steel alloys, and mechanical microindentation experiments on cast alloys of the same composition. Our results suggest that, while significant CSRO is predicted in the simulations, there is little experimental evidence in cast and annealed alloys analyzed by APT.

Experimental and statistical investigation into surface characteristics in micro milling of bottom pouring/gravity stir cast Al6061 alloy

Micro milling offers the best way to create micro channels; however, the burr formation and surface roughness of the micro channel are difficult to control. Micro channel fabrication and their characterization of stir cast Al6061 are rarely investigated. In the present study, Al6061 alloy was processed by the bottom pouring stir casting method. The micro channels were fabricated on a base and stir cast Al6061 alloys using TiSIN-coated micro end mill tools. The influence of micromachining parameters such as spindle speed, feed rate, and depth of cut on burr formation, cutting force, burr size, and surface roughness was investigated. A comparison was made between the findings obtained from the micro milling of the base and stir cast Al6061 alloys. The surface morphology of fabricated micro channels was analysed and correlated with the roughness profile to understand the channel profile and burr formation. The top burr formation mechanism in stir cast Al6061 alloy was investigated in detail. Low feed rate, low depth of cut, and high spindle speed produced the micro channel with fewer burrs, low surface roughness, and low cutting forces. At the optimum parameter, stir cast Al6061 alloy showed an approximate 420%, 16%, and 300% increase in Fy, Fz, and Ra, respectively, as compared to the base Al6061 alloy. Adhesion wear, built-up edge, and microchipping were found to be the main tool wear mechanisms in micro machining of stir cast alloy. This study directs the choice of cutting parameters for the stir cast micro milling process.

An investigation of process parameter influences on dissimilar friction stir welding of cast aluminum alloy joints

ABSTRACTCast alloys find suitable employability in industrial applications favoring automotive and aerospace sectors owing to their high specific strength, low porosity, excellent fluidity, and machinability. The present study focuses on friction stir welding of cast aluminum alloys (AA356 and AA2014) with a varied range of process parameters, namely, tool pin shape (cylinder, cone, square, and threaded cylinder), tool speed (1800–2100 rpm), and tool feed (5–20 mm min−1). The novelty of the present work spotlights/features the implementation of L16 orthogonal design with the analysis of variance, grey relational analysis, fuzzy logic system, and artificial neural network approaches to contemplate the weld quality of cast joints. The microstructural analysis and grain size estimation is comprehended in the study. Regression models have been developed based on the analysis of variance. The prime factors favoring the ultimate tensile strength and microhardness were 2100 rpm, 10 mm min−1, and threaded cylinder shape. The findings from the analysis of variance and grey relational analysis are in concurrence with each other. The results of fuzzy logic showcased a substantial improvement in terms of grey relational grade. The results from the artificial neural network deliver rational evidence for the analysis of variance conducted on the selected tool pin shapes.

Robotic friction stir welding in lightweight battery assembly of extrusion-cast aluminium alloys

The present study focuses on developing lightweight assembly of two different aluminium alloys extruded and high pressure die cast (HPDC) for battery frame assembly in BEV. The goal is to produce defect-free welds in lap configuration with smooth surface finish. Stationary shoulder friction stir welding (SSFSW) was employed with welding speeds of 3–15 mm/s. EBSD analysis revealed two groups of grains in the stir zone (SZ) due to dynamic recrystallization. Moreover, the grain size of the SZ significantly decreased compared to both alloys. The cast alloy contains large iron particles, and that were broken by the rotating probe, and the stirred material consisted of fine dispersed precipitates. Tensile-shear test found the fracture location at the hook area near to cast, and a model representing fracture behavior is also discussed. With increasing welding speed from 3 to 5 mm/s, the tensile strength found ∼95 and ∼100 MPa, respectively without any significance difference in the fracture behavior and location. Overall, this study provides valuable insights such as materials mixing, grain refinement, and joint strength in dissimilar joining using SSFSW. The findings could be useful in developing optimized welding parameters and improving the overall quality and productivity of the SSFSW process for battery pack assembly in BEV.

Joining of Aluminum and CFRP via Laser Powder Bed Fusion: Influence of Experimental Set-Up and Laser Processing on Microstructure and Mechanical Properties.

Additive-manufacturing-based joining methods enable tailored or even functionalized joints and allow for hybridization at small scales. The current study explored an innovative joining method for aluminum cast alloys (AlSi12) with thermoset carbon-fiber-reinforced polymers (CFRPs) via laser powder bed fusion (LPBF). The direct build-up of AlSi12 on a CFRP substrate proved to be challenging due to the dissimilar thermal properties of the considered materials, which led to substrate damage and low joint adhesion. These effects could be overcome by introducing an AlSi12 foil as an interlayer between the two joining partners, acting as a thermal barrier and further improving the AlSi12 melt wettability of the substrate. Within LPBF, the energy input in the form of volumetric laser energy density influenced both the porosity of the fused layers and the formation of thermally induced stresses due to the high cooling rates and different thermal expansion properties of the materials. While the AlSi12 volume density increased with a higher laser energy input, simultaneously increasing thermal stresses caused the debonding and deformation of the AlSi12 foil. However, within a narrow processing window of laser parameters, the samples achieved remarkably high shear strengths of τ > 20 MPa, comparable to those of conventional joining methods.

Microstructure and mechanical properties of friction stir processed Zn-Mg biodegradable alloys

Magnesium, iron and zinc-based alloys are potential metallic biodegradable alloys for bioimplant applications. The issues of hydrogen evolution along magnesium’s surface and the release of bulky corroded products of iron alloys during its usage necessitated to look for an alternate alloy system for biodegradable implant applications. Zn-Mg alloy is one such alternate alloy that is widely explored by several researchers. The typical cast microstructure of Zn-Mg alloy contains pro-eutectic α-Zn and eutectic mixture of α-Zn and Mg2Zn11. The cast alloy exhibits poor ductility as the intermetallic Mg2Zn11 phase exists only in eutectic mixture. Therefore, the cast alloys were subsequently processed through hot rolling, hot extrusion and rarely through severe plastic deformation to enhance the mechanical properties. In the current study, probably for the first time, friction stir processing (FSP) has been used to refine the microstructure of Zn-Mg alloys with an intention to enhance the mechanical properties. Indeed, it was a challenge to friction stir process the Zn alloys through friction stir processing, as they have poor ductility (< 10 %) in as-cast condition. By choosing tool rotational speed that can impart significant heat input to the processed regime, this study demonstrated successful FSP of Zn and Zn-(0.5, 1.0 & 2.0) wt% Mg alloys. The pure-Zn and Zn-Mg alloys are FSPed using constant tool traverse speed of 20 mm/ min and variable rotational speeds of 560, 710 and 900 rpm. Hardness of as-cast Zn was 32 VHN whereas addition of 2 % Mg increased it to 105 VHN. Hardness of zinc increased to 39 VHN after FSP using 560 rpm; at the same time, further increase of rotational speed retained the hardness around 40 VHN. On the other hand, hardness of Zn-Mg alloys significantly improved after FSP. Interestingly, hardness of alloys increased with the rotational speed. Usually, increase of rotational speed increases heat input in to the processed regime thus assists the development of coarse microstructure results in hardness degradation. An opposite trend has been observed in the current study. The reasons for this notable observation are found to be refinement of microstructure and redistribution of Mg2Zn11 phase throughout α-Zn matrix that happened during FSP.

Thermomechanical Joining of Hypoeutectic Aluminium Cast Plates

Consistent lightweight construction in the area of vehicle manufacturing requires the increased use of multi-material combinations. This, in turn, requires an adaptation of standard joining techniques. In multi-material combinations, the importance of integral cast components, in particular, is increasing and poses additional technical challenges for the industry. One approach to solve these challenges is adaptable joining elements manufactured by a thermomechanical forming process. By applying an incremental and thermomechanical joining process, it is possible to react immediately and adapt the joining process inline to reduce the number of different joining elements. In the investigation described in this publication, cast plates made of the cast aluminium alloy EN AC-AlSi9 serve as joining partners, which are processed by sand casting. The joining process of hypoeutectic AlSi alloys is challenging as their brittle character leads to cracks in the joint during conventional mechanical joining. To solve this, the frictional heat of the novel joining process applied can provide a finer microstructure in the hypoeutectic AlSi9 cast alloy. In detail, its Si is finer-grained, resulting in higher ductility of the joint. This study reveals the thermomechanical joining suitability of a hypoeutectic cast aluminium alloy in combination with adaptively manufactured auxiliary joining elements.