As-cast Microstructure Research Articles

SiC nanoparticles additions to squeeze-cast Mg-5.0Al-2.0Ca-0.3Mn alloy: An evaluation of microstructure and mechanical properties

The influences of the SiC nanoparticles (SiCnp) content on the microstructural modification and mechanical properties of the squeeze-cast Mg-5.0Al-2.0Ca-0.3Mn (AXM520) alloy have been investigated. The concentrations of the SiCnp are varied from 0.5 to 3.0 (wt%), and the nanocomposites (NCs) are abbreviated as NC0.5SiC, NC1.0SiC, NC2.0SiC and NC3.0SiC. The as-cast microstructures of the AXM520 alloy and NCs consist of an α-Mg phase, a eutectic of α-Mg and (Mg,Al)2Ca (C36), and an Al8Mn5 phase. Additionally, the SiC phase is also present in the NCs. The continuous network of the C36 phase is fragmented and becomes discontinuous as the content of the SiCnp increases in the NCs. All the NCs exhibit superior tensile and compressive properties than the AXM520 alloy. The NC2.0SiC exhibits the best tensile properties among the NCs employed. The YS of the NCs improves with the increase in the SiCnp content up to 3.0 (wt%). The UTS and %El of the NCs increase up to 2.0SiCnp (wt%), and beyond that, the same declines owing to the agglomeration of the nanoparticles. The discontinuous network of the C36 phase in the NCs inhibits crack propagation, leading to their improved %El. All the NCs exhibit higher strain-hardening exponent (n) and strain-hardening rate (SHR) compared to the AXM520 alloy. The superior ‘n’ and SHR exhibited by the NCs were attributed to the grain refinement and dislocations generation. The strengthening from CTE mismatch contributes the most to the overall strengthening of the NCs. The ‘Zhang and Chen’ model is modified by introducing an agglomeration factor, and the predicted YS of the NCs matches pretty well with the experimentally obtained values.

Microstructure and mechanical properties of cast, eutectic Al-Ce-Ni-Mn-Sc-Zr alloys with multiple strengthening mechanisms

The effects of Ni additions on microstructure and microhardness of near-eutectic Al-9Ce-xNi-0.75Mn-0.18Sc-0.12Zr (x = 2.5, 3.2, and 3.9 wt.%) alloys are investigated for various cooling rates. The as-cast microstructure consists of fine, micron-scale Al11Ce3 and Ni-rich phases formed during eutectic solidification. Two Ni-rich phases are observed: (i) Al27Ce3Ni6 at higher Ni contents and slower solidification rates, and (ii) Al9(Ni,Mn,Fe)2 at lower Ni contents and faster solidification rates. While these Ni-containing alloys have higher microhardness than a Ni-free control alloy, varying the Ni concentration in the 2.5–3.9 wt.% range does not significantly affect the microhardness, indicative of competing strengthening and weakening effects from adding Ni. The alloy with intermediate Ni content (3.2 wt.%) is selected for further microstructural and mechanical characterization. It contains four coarsening-resistant strengthening constituents: (i) micron-scale Al11Ce3 and (ii) Al27Ce3Ni6 or Al9(Ni,Mn,Fe)2 platelets, all formed during eutectic solidification, (iii) L12-Al3(Sc,Zr) nanoprecipitates formed on aging, and (iv) Mn atoms in solid solution in the α-Al matrix. The combined strengthening mechanisms impart high strength at ambient and elevated temperatures, as measured by microhardness (as a function of aging time), by compression and tensile experiments, and by compressive creep measurements. Alloys previously reported in the literature - with various combinations of one, two or three of these four strengthening phases - show lower hardness and creep resistance, indicating that cumulative strengthening can be achieved when combining mechanisms; the present alloy containing all four phases shows a remarkably high creep threshold stress of 62 MPa at 300 °C.

Laser remelting of a novel carbide-reinforced Ni-Co-Cr-Hf-C alloy with ultra-fine HfC dispersion

The dispersion of stable nano-particles is essential for improving the high temperature creep properties of Ni-base alloys. Additive manufacturing by laser powder bed fusion (LPBF) offers novel means to tailor particle distributions taking advantage of the fast and directional solidification inside travelling melt pools. To benefit of this opportunity, a novel in-situ carbide reinforced alloy Ni − 32Co − 28Cr − 3.5Hf − 0.25C (wt. %) was developed. In a first rapid approach laser remelting of a cast alloy block was used to mimic LPBF solidification conditions. After a subsequent annealing treatment at 1150 °C for 6 h, an ultra-fine and intragranular dispersion of nano-sized HfC particles was obtained. The HfC particles have an average size of 54 nm and a mean inter-particle distance of 326 nm, which is an exceptional refinement compared to the as-cast microstructure. The number density of HfC particles ranges around 1 × 1012/m2 in 2D and is estimated to be 2 × 1019/m3 in 3D.

The Effect of Heat Treatment on the Mechanical Properties and Oxidation Resistance of AlSi10Mg Alloy

In this study, the microstructure, hardness, tensile strength, and dry wear properties of the cast AlSi10Mg alloy as well as the effects of processing parameters on the oxidation behavior of this alloy were investigated. In this context, AlSi10Mg (wt%) alloy was produced by gravity die casting method, and then, air cooling, quenching, and T6 treatment were applied. The microstructure of the alloy was investigated using an optical microscope, SEM, and EDS. Additionally, thermogravimetric analysis (TGA) was used to determine the effect of processing parameters on the oxidation behavior of the samples. The friction and wear properties of the alloy were investigated using a ball-on-disk wear test device. It was founded that the as-cast AlSi10Mg alloy's microstructure contained phases of α(Al), Si, and β-Mg2Si. It has been observed that the microstructure of the cast AlSi10Mg alloy gradually turns into a spherical form when quenching and air-cooling heat treatments are applied. Also, T6 heat treatment led to further spheroidization of Si particles, formation of β-Mg2Si precipitates, and elimination of the Chinese script morphology of the β-Mg2Si phase. It was observed that the yield strength of the AlSi10Mg alloy in the as-cast state decreased negligibly compared to the air-cooled state, while there was an increase of up to 70% in the aging-treated condition. The results show that the tensile strength of the as-cast AlSi10Mg alloy increased by 115% after aging. Additionally, it was found that the AlSi10Mg alloy's wear resistance increased with the aging process.

In-situ EBSD study on twinning activity caused by deep cryogenic treatment (DCT) for an as-cast AZ31 Mg alloy

This work studied the activation of the twins in a commercial cast AZ31 Mg alloy by deep cryogenic treatment (DCT) using in-situ EBSD. The initial as-cast microstructure has a range of grain sizes. The DCT mainly activated twins in the areas of fine grain size, in which the twin area fraction increased with increasing DCT time. These twins were {10–12} extension twins, which were evoked and facilitated by the large tensile interior stress that was caused by the large temperature difference during the DCT. Furthermore, only {10–12} extension twins were activated. The activated {10–12} extension twins had the highest Schmid factor and conformed to Schmidt's law. One or two other kinds of tensile twinning variants of the six tensile twinning variants (V1–V6) were activated by the DCT. These activated variants had the highest Schmid factor and the lowest orientation difference (less than 10o), while those non-activated variants had an orientation difference of ∼60o. Theoretical evaluation indicated that these two kinds of tensile twinning variants were the para-position variant rather than the ortho-position variant or the meta-position variant.

Study on the as-cast microstructure and mechanical properties of 35CrMo steel based on electric field control

Herein, the effect of current on the solidification microstructure and properties of 35CrMo structural steel has been studied. The effect of an electric field on the solidification structure of an ingot was investigated by immersing two parallel electrodes into the free surface of molten steel. Using the interaction between the current and melt as well as the Lorentz force generated by its own induced magnetic field, the whole region of the melt was covered with an eddy current. The numerical simulation of the ingot solidification process has been carried out and its influence on the inner flow field during the ingot solidification control process discussed. The results showed that an applied electric field caused turbulence inside the ingot, which drove the molten alloys to rotate and stir, refined the solidification structure, reduced the solidification defects, such as shrinkage cavity and segregation, and increased from 549.9 MPa at the top edge of the ingot and 411.4 MPa at the middle edge to 560.2 and 510.2 MPa, respectively. In addition, the electric field made the hardness and strength of each part of the ingot more uniform and improved the quality of its rigidity for the steel production process.

Effect of Hf addition on structural transformation and aging stability of Cu–15Ni–8Sn alloy

The Cu–15Ni–8Sn-xHf (wt.%, x = 0–0.6) alloys were prepared by vacuum melting, and the effect of Hf on the micro-structure of as-cast, as-solution-treated and as-aged alloys was systematically investigated, as well as the alloy aging stability. The Hf addition provided a significant role on refining the solidification structure and reducing the micro-segregation degree, and it also made γ-D03 phases more likely to form in needlelike-shape rather than lamellar-shape. With the presence of more Hf atoms, their existence form was accordingly changed from solid solute atoms to nano-scale precipitation phases and then to micron-scale segregation phase. A small content of Hf (0.1 wt%) could effectively improve the aging stability by inhibiting the growth of γ-D03. Once its content reached or exceeded 0.3 wt%, the harmful discontinuous precipitation was completely inhibited, and the common lamellar-shape γ-D03 locating around the grain boundary was no longer formed. Even the alloy failed at higher temperatures, it could only be carried out through the continuous precipitation method, namely the generation of needlelike-shape γ-D03 uniformly in the matrix. The appropriate Hf addition was capable of extending the alloy aging window, and the hardness of Cu–15Ni–8Sn-0.3Hf alloy could still exceed 360 HV even after 48 h aging.

The influence of La and Ce additions on the solidification of alloys from the Al–Fe system

AbstractAluminium alloys are popular in modern applications due to their lightweight, high strength and ductility. Alloys in the 8xxx series have similar properties to those in the 1xxx series, but are stronger, are more malleable and have higher stiffness. The addition of rare earths (RE) can refine the as-cast microstructure and, as a result, can increase the corrosion resistance and mechanical properties of aluminium alloys at room and high temperatures. The effects of rare earth (Ce and/or La) additions to Al-1.4Fe alloys were investigated. Thermal analysis of the solidification behaviour of the reference alloy showed the occurrence of three reactions corresponding to the formation of α-Al, eutectic (α-Al + AlxFey) and Fe intermetallics, respectively. The results showed similar reactions for the Ce- and/or La-modified alloy, but at slightly different temperatures, indicating a change in the forming phases due to the addition of Ce and/or La. In all cases, the microstructures were typically hypoeutectic, consisting of the primary α-Al and the eutectic (α-Al + AlxFey). The effect of grain refinement of the primary α-Al grains of the as-cast alloy was observed by the addition of RE, while La showed the strongest effect. The effect of the RE additions showed no obvious differences in the morphology of the eutectic AlxFey, although they were present in these phases. When Ce and/or La were added, (α-Al + Al11Ce3) and/or (α-Al + Al11La3) eutectics were formed, while Fe was not detected in these eutectics.

Influence of Investment Casting Manufacturing Conditions on As-Cast Microstructure and Erosive Wear Resistance of 26%Cr Cast Iron

Influence of Investment Casting Manufacturing Conditions on As-Cast Microstructure and Erosive Wear Resistance of 26%Cr Cast Iron

Effect of compositional minor adjustment on localized lamellar structure coarsening of TiAl alloys with different solidification modes

Possible lamellar coarsening in the as-cast microstructure of TiAl alloys significantly affects the subsequent processing of ingot metallurgy, and a systematic study of it is necessary. In this paper, two TiAl alloys with different solidification modes (TNM-45Al alloy and TNM-0.3Si-0.7 C alloy) were obtained by compositional minor adjustment basing on TNM alloy. The effect of different adjustment routes on the localized lamellar structure coarseing behaviour and the resulting differences in the uniformity of the nanohardness distribution were investigated by comparing with TNM alloy. It is found that increasing the Al content of the TNM alloy while keeping the solidification mode as β-solidification unchanged leads to severe localised lamellar coarsening in the S-segregation zone of TNM-45Al alloy, including continuous coarsening (CC) and discontinuous coarsening (DC). In contrast, the solidification mode of the TNM-0.3Si-0.7 C alloy with the addition of the strong α stabilizer elements Si and C is transformed into hypoperitectic solidification with severe peritectic segregation, but the lamellar structure exhibits surprising full-domain stability. The results show that the thermodynamic tendency caused by high Al content and the absence of net-like β-segregation leads to severe localised lamellar coarsening in TNM-45Al alloy. CC can be accomplished through the migration of interface defects. DC is formed by the nucleation and expansion of γ-phase Shockley incomplete dislocations, and the interfaces consist of the α2 /γ interface and the first discovered γ /γ twin interface. The lamellar coarsening of TNM-0.3Si-0.7 C alloy can be effectively suppressed by the solid solution of Si/C atoms and the near net-like β-segregation in the primary β-phase region. As a result, the distribution uniformity of the nanohardness of the lamellar structure in TNM-0.3Si-0.7 C alloy is excellent, with the variance decreasing from ±0.24 of TNM alloy to ±0.20, while it increases to ±0.37 for the TNM-45Al alloy.

Effect of Coupling Low-Flow Pouring with Inoculation on the As-Cast Microstructure of 7055 Alloys

Effect of Coupling Low-Flow Pouring with Inoculation on the As-Cast Microstructure of 7055 Alloys

Effect of In Situ NbC-Cr7C3@graphene/Fe Nanocomposite Inoculant Modification and Refinement on the Microstructure and Properties of W18Cr4V High-Speed Steel.

A novel graphene-coated nanocrystalline ceramic particle, iron-based composite inoculant was developed in this study to optimize the as-cast microstructure and mechanical properties of W18Cr4V high-speed steel (HSS). The effects of the composite inoculant on the microstructure, crystal structure, and mechanical properties of HSS were analyzed using transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The (002-) and (020) crystal planes of the Fe3C and Cr7C3 phases, respectively, were collinear at two points in the reciprocal space, indicating a coherent relationship between the Fe3C and Cr7C3 phases in the tempered modified HSS. This contributed to an improved non-uniform nucleation rate and refining of the HSS grains. The mechanical properties of the modified steel exhibited a general improvement. Specifically, the modification treatment enhanced the hardness of HSS from HRC 63.2 to 66.4 and the impact toughness by 48.3%.

Tailoring Multiple Strengthening Phases to Achieve Superior High-Temperature Strength in Cast Mg-RE-Ag Alloys.

Mg alloys with excellent high-temperature mechanical properties are urgently desired to meet the design requirements of new-generation aircraft. Herein, novel cast Mg-10Gd-2Y-0.4Zn-0.2Ca-0.5Zr-xAg alloys were designed and prepared according to the advantages of multi-component alloying. The SEM and XRD results revealed that the as-cast microstructures contained α-Mg grains, β, and Zr-containing phase. As Ag rose from 0 wt.% to 2.0 wt.%, the grain size was refined from 40.7 μm to 33.5 μm, and the β phase significantly increased. The TEM observations revealed that the nano-scaled γ' phase could be induced to precipitate in the α-Mg matrix by the addition of Ag. The stacking sequence of lamellar γ' phases is ABCA. The multiple strengthening phases, including β phase, γ' phases, and Zr-containing particles, were effectively tailored through alloying and synergistically enhanced the mechanical properties. The ultimate tensile strength increased from 154.0 ± 3.5 MPa to 231.0 ± 4.0 MPa at 548 K when Ag was added from 0 to 2.0 wt.%. Compared to the Ag-free alloy, the as-cast alloy containing 2.0 wt.% Ag exhibited a minor reduction in ultimate tensile strength (7.0 ± 4.0 MPa) from 498 K to 548 K. The excellent high-temperature performance of the newly developed Mg-RE-Ag alloy has great value in promoting the use of Mg alloys in aviation industries.

Mechanical properties and corrosion behavior of electron beam cold hearth melting high strength and high corrosion resistant Ti-0.3Mo-0.8Ni alloy with different states

In this study, a large size Ti-0.3Mo-0.8Ni (TA10) alloy ingot melted by electron beam cold hearth melting (EBCHM) technology was investigated. The microstructure, mechanical properties, and corrosion behavior of as-cast, hot-rolled, and annealed TA10 alloys were investigated. The results show that different states of TA10 alloys have different microstructure and properties. The microstructure of the as-cast TA10 alloy exhibits the Widmanstätten α phase, and the hot-rolled TA10 sheet shows a fibrous structure with an obvious rolling streamline. After 650 °C annealing, the intergranular β phase decreases, and most of the strip α phase changes to the equiaxed α phase. With the annealing temperature increasing to 840 °C, the microstructure gradually changed from an equiaxed structure to a duplex structure. The mechanical properties of the TA10 alloy were enhanced after hot-rolling with an increase in ultimate tensile strength from 386.5 MPa to 610 MPa. Additionally, the elongation increased from 15.6 % to 23.3 %. Upon annealing at varying temperatures, it was observed that the strength decreased, reaching to 423.5 MPa at 650 °C and 478.2 MPa at 840 °C, while the plasticity increased significantly, reaching to 26.5 % at 650 °C and 28.6 % at 840 °C. The improved strength was attributed to the better grain boundary slip of the equiaxed structure. The corrosion resistance of titanium alloys is closely connected with their microstructure. The results of the immersion corrosion test indicate that the samples in various states exhibit similar corrosion behavior. Additionally, the hot-rolled TA10 alloy shows the highest corrosion resistance, with a lower corrosion rate of 0.34459 mm/year. The as-cast TA10 alloy shows the lowest corrosion resistance, with a lower corrosion rate of 1.37559 mm/year.

Microstructure and properties of Mn–Si–Cr alloy steel modified by quenching and partitioning

Abstract This study investigates the influence of modification on the microstructure and properties of Mn–Si–Cr alloy steel. The results indicate that the as-cast microstructure of Mn–Si–Cr alloy steel is composed of black acicular bainitic ferrite lath and white retained austenite. The microstructure of the alloy steel changes to martensite, austenite, and carbide after quenching and partitioning treatment. After rare-earth magnesium modification and compound modification, the as-cast microstructure of Mn–Si–Cr steel becomes more refined and displays a more regular arrangement. Furthermore, the martensite and austenite grains in the modified samples show refinement, and the arrangement of martensite is more systematic. Additionally, the amount of austenite decreases, and the amount of carbides increases after quenching and partitioning heat treatment. In comparison with the unmodified samples, the modified samples show negligible changes in hardness. However, the impact toughness of modified quenched and partitioned steel increases by 20 %. Moreover, the wear resistance of compound modified quenched and partitioned steel is 38 % higher than that of the unmodified sample. The compound modified sample steel exhibits excellent wear resistance and comprehensive mechanical properties.

Solidification microstructures of V-Nb-Mo-Ta-W alloys: Insights from non-equiatomic alloys

We have investigated the solidification microstructures of the non-equiatomic and equiatomic V-Nb-Mo-Ta-W alloys, which are one of the first refractory high entropy alloys, and found intriguing dual body-centered cubic (BCC) microstructures. There were two issues to be addressed in these alloys: an unidentified strengthening mechanism and intense microsegregation in the as-cast state. We determined that the as-cast microstructure of the non-equiatomic V14Nb19Mo20Ta24W23 and V22Nb24Mo24Ta24W10 alloys consist of two BCC phases with different lattice constants, and that the equiatomic alloy of the V-Nb-Mo-Ta-W system consists of two BCC phases with different compositions but the same lattice constants. The two BCC phases form lattice-matched interfaces, suggesting that precipitation-hardening with high lattice-matching can be one of the reasons for the excellent high-temperature mechanical properties of this alloy system. In addition, we also found that the alloys that were poor in V and Nb, and rich in Ta and W compositions solidified without precipitating of secondary BCC phases. The alloys in this compositional range have partition coefficients of the elements closer to 1 than those with near-equiatomic compositions.

Mechanism of the synergistic effect of solid solution strengthening and fine grain strengthening in an as-cast Cu–9Ni–6Sn alloy induced by Mn

The effects of Mn content on the Sn distributions, grain sizes, second phases, and mechanical properties of Cu–9Ni–6Sn-XMn alloys (wt.%, X = 0, 0.1, 0.5, and 1.0) were studied in this paper. The mechanisms of acting and strengthening through which Mn could promote grain refinement in the alloy were discussed. The results showed that the addition of Mn transforms the as-cast microstructure of the alloy into equiaxed grains, and the grains are obviously refined. When the amount of Mn is approximately 0.1 wt%, the average grain size of this alloy is 91.75 μm, and the grain refinement effect is greatest in the experimental range. In addition, Mn increases the uniformity of the distribution of Sn in the as-cast microstructure. Differential scanning calorimetry (DSC) analysis revealed that the addition of Mn increases the undercooling of the as-cast Cu–9Ni–6Sn alloy and decreases in the critical nucleation radii of the grains. Further microstructure observation showed that Mn is dissolved mainly in the γ-(Cu,Ni)3Sn phase. Consequently, the interfacial relationship between the γ-(Cu,Ni)3Sn phase and the matrix transforms from incoherent to semicoherent. Compared with those of the Cu–9Ni–6Sn alloy, the strength and elongation of the alloy with added Mn are relatively great. When the content of Mn is 0.1 wt%, the strength of the alloy increases from 359.75 MPa to 423.54 MPa, while the elongation remains at 19.14 %. The synergistic effect of solution strengthening and fine grain strengthening of Mn is the main reason for the great improvement in the mechanical properties of the alloy.

Designing of novel microstructure and its impact on the improved service temperature mechanical performance of 2nd and 3rd generation advanced intermetallic TiAl alloys

Advanced lightweight TiAl based intermetallic systems, capable of surviving elevated temperatures, have been a topic of interest, considering their ever-increasing demands in aerospace industries. The optimization of solidification and processing methods stands as a pivotal factor in microstructural engineering for TiAl systems, aiming to attain desired mechanical properties. The present study focuses on two distinct alloy systems, a commercial grade 2nd generation, i.e., Ti–48Al–2Cr–2Nb (at. %), and a newly developed 3rd generation, i.e., Ti–45Al–2Cr-7.5Nb-0.2B (at. %) alloys. Interestingly, the variation in the solidification path, triggered by higher Nb content along with a minor amount of B, accounts for the substantial microstructural refinement for the 3rd generation TiAl alloy. Nevertheless, prominent segregation of Nb and Cr to the β0 phase is observed in both the as-cast microstructure, which restricts the applicability of the alloys. Remarkably, a novel bilamellar-biglobular (BLBG) microstructure consisting of γ and α2 phases in both lamellar and globular morphologies is achieved through heat treatment for both categories of alloy. Elevated temperature tensile testing depicts an exceptional strength-ductility combination for 3rd generation BLBG microstructure. Excellent twin-twin activity and twin-induced plasticity effect are observed to govern the deformation mechanism. Overall, the path of solidification, phase distribution, and its effect on the deformation mechanism are thoroughly analyzed, which is of particular interest from a design and application point of view.

Quasi-in-situ investigation on complete lamellar fragmentation of β-solidified TiAl alloy during uniaxial isothermal compression

The coarse as-cast lamellar microstructure in TiAl alloys is difficult to be broken completely by thermomechanical processing. Some remnant lamellar colonies in the deformed microstructure seriously affect the microstructural homogeneity and deteriorate the properties. In this study, it is found that by isothermal compression at 1230 °C and 1250 °C, the lamellar colonies of Ti-43.5Al-4Nb-1Mo-0.1B (TNM) alloys can be completely broken. This is attributed to the weakened anisotropic deformation behavior of the lamellar colonies due to the isothermal holding treatment before deformation. The deformation behavior at 1230 °C was investigated by quasi-in-situ experiments. It is observed that the regions near lamellar colony boundaries first undergo dynamic recrystallization at small strain, while the lamellar colonies gradually break down with increasing strain. The adequate fragmentation of lamellar colonies mainly depends on the recrystallization of α lamellae (αL). The isothermal holding at 1230 °C leads to an increase in the content and thickness of αL, which allows it to assume more deformation and promotes its recrystallization by reaching critical strain. The interrupted γ lamellae (γL) formed by decomposition during isothermal holding facilitates the occurrence of α recrystallization within the lamellar colonies by hindering dislocation movement. In addition, recrystallized γ grains (γR) are gradually dissolved by the formation of α precipitates inside them through the γ → α phase transformation and the subsequent consumption of α precipitates by the recrystallized α grains.

Effects of Cr-addition on ageing response of an Al–Si–Mg die cast alloy

Chromium (Cr) is rarely added to Al–Si die cast alloys as it has a strong tendency to induce the formation of coarse-sized sludge particles. In the present study, high pressure die-cast samples made of Al-7wt.%Si–Cr–Mg alloys with varied Fe contents (0.11 wt%, 0.26 wt% and 0.32 wt%) were tensile tested under as-cast and T5 heat-treated conditions, in comparison to those made of Al-7wt.% Si–Mn–Mg alloy with a constant Fe content (0.11 wt%). The results demonstrated that under the as-cast condition, the Al–Si–Cr alloys with higher Fe contents can achieve comparable tensile properties as the Al–Si–Mn alloy with strictly controlled Fe level. However, after a T5 heat treatment (205 °C for 60 min), the increment in yield strength is less for the Al–Si–Cr alloys in relative to the Al–Si–Mn alloy, regardless of Fe contents. Scanning electron and scanning transmission electron microscopic characterizations were conducted on the as-cast and heat-treated microstructures, aiming to understand the undermined ageing response caused by Cr addition.