Cast A356 Alloy Research Articles

Inhibiting Eutectic Si Macrosegregation in Squeeze Cast A356 Alloy by Symmetrical Multidirectional Pressure

The process of symmetrical multidirectional pressure was adopted to inhibit the macrosegregation of eutectic Si in squeeze cast A356 alloy. Five pressure modes were applied to study the effects of multidirectional pressure and the timing of pressure application on the macrosegregation of eutectic Si. The results show that the directional movement of the solute-rich liquid phase could be inhibited by symmetrical multidirectional pressure. Therefore, the macrosegregation of eutectic Si in the casting part was inhibited. Moreover, the timing of pressure application should be matched with the local pressure position. After the effective inhibition of the macrosegregation of eutectic Si, the elongation of the alloy was significantly improved, reaching up to 7.12%. In addition, the plastic deformation region was observed at the local pressure position. The grains in the plastic deformation region were refined. The proportion of low-angle grain boundaries in the deformed region was about 30%, which was much higher than that in the other undeformed region. The size of the Fe-containing intermetallics in the deformed region decreased to 5–10 μm, which is favorable for the mechanical properties of the alloy.

Microstructure and surface characterization of copper and zinc added heat treated stir cast A356 alloy

Microstructure and surface characterization of copper and zinc added heat treated stir cast A356 alloy

Effects of Zr and Y additions on microstructure and mechanical properties of cast A356 alloy

In the present work, the effects of Zr and/or Y addition on microstructure and mechanical properties of cast A356 alloy were investigated using X-ray diffractometer (XRD), differential scanning calorimetry (DSC), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The heterogeneous nucleation effect on Zr-rich phases generated by the peritectic reaction, the increased constitutional undercooling caused by Y addition and serve as surfactant led to the grain refinement. Besides, The average size of eutectic Si reduced from 8.5 μm in the base alloy to 6.2, 1.3, and 1.7 μm with the addition of Zr/Y/Zr + Y, respectively. Zr can slightly refine eutectic Si due to the limited growth space caused by grain refinement, while Y can modify the morphology of eutectic Si from plate-like into fibrous-like through high density twins formed by the IIT mechanism. The optimal mechanical properties are obtained when Zr and Y are added simultaneously with the ultimate tensile strength, yield strength, and elongation values of 104 MPa, 201 MPa, and 7.6%, respectively. The YS and UTS increase was due to grain-refining, Si modification and precipitation strengthening. The enhancement of El was mainly caused by Si modification, which reduced the possibility of crack initiation and propagation at Si/α-Al interfaces.

Influence of tool geometry on mechanical and microstructural characteristics of friction stir welded cast alloys

Abstract Cast alloys find suitable applicability in aerospace sector owing to low porosity, high specific strength, corrosion resistance, fluidity and good machinability. The investigation focuses on friction stir welding (FSW) of cast A356 and A2014 alloys with varied range of process parameters, namely tool pin shape (cylinder, threaded cylinder, square, and conical), tool rotation speed (1800–2100 rpm) and welding speed (10–25 mm × min−1). Experimentation on stirwelding was performed based on selected tool pin shape between varied tool rotation and welding speed. The output responses, namely Ultimate tensile strength (UTS) and micro hardness, have been evaluated to study the effect of each tool. The microstructural characteristics of the weld samples were analyzed using optical microscope and scanning electron microscope (SEM) technique. The microstructural observation unveiled that complete fusion prevails between the parent alloys devoid of micro porosities and segregations. The re-crystallization effect resulted in the finer grains. The cylinder-shaped tool with a thread and square shaped tool rendered better strength and hardness properties of 136.6 MPa and 109.4 HV, respectively.

To improve robustness of mechanical properties of semi-solid cast A356 alloy using taguchi design method

To improve robustness of mechanical properties of semi-solid cast A356 alloy using taguchi design method

Effect of refractory aggregate shape on the porosity of A356 alloy castings in lost foam casting

Effect of refractory aggregate shape on the porosity of A356 alloy castings in lost foam casting

An investigation into the softening behavior of cast A356 alloy in the solid and semisolid deformation regimes

The current work deals with the hot deformation behavior of A356 aluminum alloy starting with the cast structure and an emphasize on the capability of flow softening. Toward this end, the hot compression tests were performed at temperatures of 150, 250, 350, 450, 500 and 550 °C in the solid range and 580 °C in the semisolid range under the typical strain rate of 0.01s−1. The materials represent high protentional for the occurrence of softening mechanism in solid state regime. During thermomechanical processing (above 250 °C), after reaching the peak stress, the dynamic recrystallization prevails over the deformation behavior and the stress level reaches a steady state regime. The α-dendritic arms are crushed and refined, and the silicon blades are mechanically fragmented and spread irregularly through the microstructure. Being in the semi-solid temperature range, the eutectic silicon phase is melted and causes a sharp decrease in the resistance against deformation. The penetration of the liquid phase along the developed sub-boundaries give rise to grain partitioning and resembles the occurrence of dynamic recrystallization. The presence of the liquid phase during semisolid forming, in addition to the lubricated flow mechanism, facilitates the deformation by providing proper condition for the occurrence of recrystallization. In the present case, a stable stress level as below as 1 MPa was recorded for the experiment cast structure.

Effect of the Cooling Capability Difference Between Additively Manufactured Sand Molds on Shrinkage Defect in A356 Alloy Castings

Effect of the Cooling Capability Difference Between Additively Manufactured Sand Molds on Shrinkage Defect in A356 Alloy Castings

Fabrication, testing, and microstructural analysis of nitinol-based self-healing metal matrix composite of A356 alloy cast by semi-solid metal processing

ABSTRACT The self-healing of metallic material is a relatively new area in materials engineering. It is inspired by the biological process of healing. This work analyzes the self-healing behaviour of metals-matrix composite. The semi-solid metal processing technology was opted to prepare an aluminium-based self-healing metal-matrix composite. Nitinol is the alloy produced by combining nickel and titanium in a 1:1 ratio, with the wires of the same incorporated within the aluminium matrix during the process. Analysis of the recovery rate of the self-healing material and microstructural investigation of the metal matrix composite is the objective of this research work. The deployment of shape memory wire provides the ability to recover the matrix material even from plastic strain. Nitinol exhibits a shape memory effect by the transformation of the phase. Integration of A356 alloy with nitinol wire enables the material to regain its original shape and dimension by heat as an external stimulus. Semi-solid metal process via rapid slurry formation technique handled delicately so that self-healing effect should not diminish. Microstructural evaluation indicates fair integration of the reinforcement within the matrix material. Analysis of crack closure shows 44.277% positive recovery of the deformed surface.

Investigation of Phase Transformation and Mechanical Properties of A356 Alloy with Cu and Zr Addition during Heat Treatment

Cast A356(Al-Si-Mg) alloys are widely used in automotive and general applications because of their mechanical properties and castability. Al-Si-Mg-(Cu) alloys typically lose their strength above 170 o C due to coarsening of precipitates, which limits their application to components. To maintain their strength at elevated temperature, Al-Si-Mg-(Cu) alloys are modified by adding transitional metals. Several studies have been carried out to evaluate the effect of Zr addition on the high temperature mechanical properties of cast Al-Si alloys because Zr can form thermally stable phases such as Al3Zr. Despite the relative studies on the influence of Cu and Zr on the mechanical properties of cast Al-Si-Mg-(Cu) alloys, investigations of the effect of Zr on the phase transformations and the mechanical properties during heat treatment remains limited. In this study, the effects of added Cu and Zr on the phase transformations and the mechanical performance during heat treatment of A356 cast alloy were investigated. Needle-like and block-like (Al,Si)3(Ti,Zr) dispersoids formed as some Si and Ti replaced Al and Zr in Al3Zr crystal structures were generally observed. Furthermore, with increasing solution treatment time, the size of Zr dispersoids was reduced, and smaller Zr particles were precipitated at the same time, which caused a decrease in the area fraction of the Zr dispersoids. In addition, the metastable L12 structures of Zr dispersoids in Al-Si-Mg-Cu-Zr alloys were transformed into stable D023 during solution heat treatment as the Cu addition accelerated the transformation. Tensile and low-cycle fatigue (LCF) tests were performed to reveal the effects of (Al,Si)3(Ti,Zr) dispersoids on mechanical properties. As a result, elongation at elevated temperature was highly increased, while maintaining strength, according to the increase in solution heat treatment time, which improved low-cycle fatigue properties.

Aging and wear characteristics of A356 alloy with Er and Zr addition

The present work investigates the effect of aging on the microstructure, mechanical properties, and wear behaviour of the cast A356 alloy with Er and Zr addition. The aged A356-0.25Zr and A356-0.25Er alloys revealed some but not all of the eutectic and columnar structures. The microstructure of A356, A356-0.5Er, and A356-0.5Er-0.25Zr alloys exhibited large α-Al grains with discrete eutectic silicon. Various intermetallic types and morphologies were observed after the peak aging. The highest hardness (∼120 HV) and the highest tensile strength (∼215 MPa) were achieved in the A356-0.25Zr alloy under peak-aged conditions. The A356 alloy revealed the lowest weight loss and friction coefficient, though it had the least hardness. Delamination was the dominant wear mechanism in all alloys.

Improvement of metallurgical properties of A356 aluminium alloy by AlCrFeSrTiBSi master alloy

Abstract A new AlCrFeSrTiBSi master alloy was manufactured by in situ synthesis in Al melt, and compared with AlBSr master alloy. Microstructures of A356 alloy modified with AlCrFeSrTiBSi master alloy were investigated, and the structural details of the new cast A356 alloy were evaluated by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness and differential thermal analysis (DTA). AlBSr master alloy typically formed α-Al and granular SrB6 phases in A356, and the samples inoculated with AlCrFeSrTiBSi master alloy consisted of additionally AlCrFeSi phase with irregular blocks. The addition of 0.1 wt%AlCrFeSrTiBSi alloy to the A356 alloy significantly refined and modified the grain structure together. The structure of eutectic Si converted from acicular form to fibrous. The size of α-Al dendrites declined from ∼1000 μm to ∼100 μm. The strength values of the A356 alloy were developed by ∼70% with the addition of 0.1 wt%AlCrFeSrTiBSi master alloy.

Grain refinement and eutectic modification of A356 casting alloy by adding Al-B-Sr master alloys and its effect on tensile properties

The effects of the grain refinement and eutectic Si modification on tensile properties by using Al-B-Sr master alloys in A356 cast alloy were investigated. Two different master alloys, Al-4%B-1%Sr (4B1Sr) and Al-3%B-3%Sr (3B3Sr), were developed. In microstructure observation, the master alloys were consisted of AlB2, SrB6, AlSrF, KAlF4 and Al4Sr compounds. It should be noted that the α-Al phase also exists in two master alloy. The result showed that the AlB2 area fraction in the 4B1Sr alloy was higher than the 3B3Sr alloy. The 4B1Sr alloy has better efficiencies of α-Al grain refinement and eutectic Si modification than the 3B3Sr alloy, and α-Al grains are refined from 3035 to 312 μm and the eutectic Si is modified from the acicular to fibrous morphology. The tensile properties of 4 wt% treated with 4B1Sr alloy has higher UTS and elongation compared to the treated with 3B3Sr alloy.

Exploration of Various Forging Route Performance of Cast A356 Alloy Reinforced with Fly Ash and MWCNT Hybrid Composites

Exploration of Various Forging Route Performance of Cast A356 Alloy Reinforced with Fly Ash and MWCNT Hybrid Composites

Towards the Ductility Limit of Large Thin-Walled A356 Alloy Castings

Towards the Ductility Limit of Large Thin-Walled A356 Alloy Castings

Effect of Addition of Grain Refiner and Modifier on Microstructural and Mechanical Properties of Squeeze Cast A356 Alloy

Effect of Addition of Grain Refiner and Modifier on Microstructural and Mechanical Properties of Squeeze Cast A356 Alloy

Microstructure and fatigue strength of A356 alloy castings refined on the surface by rapid crystallization

Abstract The effect of the microstructure on the fatigue strength of A356 alloy castings with a surface refined through rapid crystallization has been investigated. The refinement of the structure, in order to improve the fatigue strength of the alloy surface, was accomplished with an electric arc plasma. The surface fusions were made in helium atmosphere by changing the welding current intensity from 100 to 300 A and the arc advance speed from 200 to 600 mm/min. The rapid crystallization reduced the parameters 𝜆1 and 𝜆2 of the 𝜆 phase dendrites and 𝜆E of the eutectic, compared to the initial material. The parameter 𝜆E changed by a factor of nearly 3. The structural refinement was determined by the amount of heat input into the fusion area. The fatigue strength increased with decreasing values of the λ parameters of the structure.

Effect of Runner Thickness and Hydrogen Content on the Mechanical Properties of A356 Alloy Castings

Earlier studies demonstrated the detrimental effect of entrained bifilm defects on aluminum cast alloys’ tensile and fatigue properties. It was suggested that hydrogen has a contributing role as it diffuses into the bifilms and swells them out to form hydrogen porosity. In this study, the effect of the runner height and hydrogen content on the properties of A356 alloy castings was investigated using a two-level full factorial design of experiments. Four responses, the Weibull modulus and position parameter of both the ultimate tensile strength (UTS) and % elongation, were assessed. The results suggested that decreasing the runner height and adopting procedures intended to decrease the hydrogen content of the casting caused a considerable enhancement of the Weibull moduli and position parameters of the UTS and % elongation. This was reasoned to the more quiescent practice during mold filling, eliminating the possibility of bifilm formation as well as the decreased hydrogen level that eliminated the amount of hydrogen diffused into the bifilms and accordingly decreased the size of the entrained defects. This, in turn, would allow the production of A356 cast alloys with better and more reproducible properties.

Effects of Heat Treatment on the Microstructure and Hardness of A356 (AlSi7Mg0.3) Manufactured by Vertical Centrifugal Casting

The A356 alloy has been widely used in automotive components, such as wheels and brake disks, because it is an excellent lightweight material with high corrosion resistance and good mechanical properties. Recently, to reduce the weight of brake disks, the Fe-A356 hybrid brake disk has been suggested. Because brake disk quality is directly related to driving safety, the T4/T6 heat treatment of centrifugally cast A356 alloys were performed to enhance the mechanical properties and reduce micro-segregation. The solid-solution heat treatment followed by annealing caused the formation of Mg-rich intermetallic compounds on the grain boundaries of the Al matrix, decreasing the average hardness of the alloys by 13 HV. In contrast, the solid solution followed by water quenching (T4) reduced the area fractions of the intermetallic compounds and increased the average hardness by 11 HV. The T6 heat-treated A356 alloys, which were influenced by the formation of the Guinier–Preston zone exhibited a relatively higher average hardness, by 18 HV, compared to T4 heat-treated A356 alloys.

Effect of Waste Titanium Chips Addition Into the Aluminum Alloys on Their Microstructure

In the present study, turning chips were preferred to add titanium into liquid aluminum. Although being easy to reach and cheap, the chips were thought to be effective in minor titanium addition with their large surface area. Experimental studies have been carried out with A356 casting alloy and commercial purity aluminum. The effects of different process parameters were investigated on titanium transfer efficiency, microstructural and microhardness properties of the formed phases. The processes were carried out between 740 - 820 °C, for 2, 4, and 6 h, with the amount of added chips 5 and 10 wt.% (3 and 6 vol.%). The experiments were conducted with both commercially pure Al and A356 alloy. The microstructural investigations and microhardness measurements were carried out on the formed Al3Ti and (Al, Si)3Ti phases. The first noticeable result was that titanium transfer was more efficient in pure aluminum than in the A356 alloy. Also, it was observed that this difference became more significant with an increase in wt.% addition. The measured microhardness values were also differentiated depending on the Si content of the formed Al3Ti compound. Due to the presence of high Si content in A356 alloy, transference efficiencies of Ti were found highly limited compared to pure aluminum as the silicon enrichment in the Al3Ti compound reduces the diffusion of titanium and the growth rate of Al3Ti particles. Maximum transference efficiency was found 47.05% with 10 %wt. chip addition in commercially pure aluminum at the processing conditions of 780 °C for 4 h.