Die-cast Aluminum Alloy Research Articles

Study on the Influence of Injection Velocity on the Evolution of Hole Defects in Die-Cast Aluminum Alloy

Aluminum alloy die casting has achieved rapid development in recent years and has been widely used in all walks of life. However, due to its high pressure and high-speed technological characteristics, avoiding hole defects has become a problem of great significance in aluminum alloy die casting production. In this paper, the filling visualization dynamic characterization experiment was innovatively developed, which can directly study and analyze the influence of different injection rates on the formation and evolution of alloy flow patterns and gas-induced defects. As the injection speed increased from 1.0 m/s to 1.5 m/s, the average porosity increased from 7.49% to 9.57%, marking an increase in the number and size of the pores. According to the comparison with Anycasting, simulation results show that a liquid metal injection speed of 1.5 m/s when filling the flow front vs. the previous injection rate of 1.0 m/s caused fractures when filling at the same filling distance. Therefore, the degree of the broken splash at the flow front is more serious. Combined with the analysis of transport mechanics, the fracturing is due to the wall-attached jet effect of the liquid metal in the filling process. It is difficult for the liquid metal to adhere to the type wall in order to fuse with subsequent liquid metal to form cavity defects. With an increase in injection velocity, the microgroup volume formed via liquid breakage decreases; thus the volume of air entrapment increases, finally leading to an increase in cavity defects.

Cyclic deformation behavior of an overaged high-pressure die-cast aluminum alloy

The aim of this study is to identify the deformation behavior of a high-pressure die-cast Silafont®-36 aluminum alloy in an overaged T7 condition in relation to the significant microstructural changes caused by the overaging heat treatment. The T7 aluminum alloy exhibited a distinctive composite-like microstructure, consisting of coarser α-Al grains and larger spherical Si particles embedded in the matrix, in contrast to its as-cast and T4 counterparts. The softer α-Al matrix of the T7 alloy as revealed by the nanohardness and microhardness led to improved ductility and longer strain-controlled fatigue life at higher strain amplitudes, despite the lower strength. Cyclic stabilization was observed to be a salient feature of the T7 alloy, stemming from the equilibrium between cyclic hardening and cyclic softening. Strain-energy density-based model, by incorporating a material parameter called ‘intrinsic fatigue toughness’, could be used to predict the fatigue life of the alloy.

Impregnation problems of aluminum castings

Abstract Vacuum impregnation is an effective solution to the porosity problem of aluminum die castings. Experience has shown that quality die-cast aluminum alloy products manufactured with gas tightness requirements can show leakage even after impregnation operation. The study seeks to answer the question of the geometry of the cavity system through which leakage occurs and why the cavity system is not saturated with liquid resin during impregnation. It is assumed that insufficient impregnation occurs if the near-surface parts of the cavity system are heavily deformed locally during the machining of the casting.

Computation method for mechanical performances of die-cast aluminum alloys based on non-uniform material properties

Integrated die casting is an effective method for the lightweight design of automobiles and for improving production efficiency. It has gained popularity in the field of new energy vehicles. When calculating the mechanical performances of integrated die-cast parts, engineers do not rigorously assume that material properties are uniform. This assumption ignores the influence of the size and internal defects on the mechanical properties of die-cast aluminum alloys, leading to the deviation of the calculation results from the actual material. Material properties are closely related to microstructure. To investigate the size effect and defect effect of the mechanical properties of die-cast aluminum alloys, the die-cast mold with varying wall thicknesses and flow lengths is designed. Die-cast tests, tensile experiments, and casting simulations are conducted to obtain the mechanical properties of JDA1b aluminum alloy at various thicknesses and defect rates. The microstructure of the JDA1b alloy with different defect rates and thicknesses is characterized. Results show that the yield strength, ultimate tensile strength, and elongation of the JDA1b alloy decrease as the defect rate increases. This work proposes a new mechanical constitutive model that considers defect rate and thickness and develops a computation method for mechanical performances of die-cast aluminum alloys based on non-uniform material properties. The methodology is applied to a large integrated die-cast part, and it effectively predicts the weakening effect of defects on the material properties. This work provides high-precision computational support for the mechanical performances of integrated die-cast parts containing defects.

Derivation of Plunger Injection Input to Prevent Gas Defects by Algebraic Approach for Aluminum Alloy Diecasting

Derivation of Plunger Injection Input to Prevent Gas Defects by Algebraic Approach for Aluminum Alloy Diecasting

Modifying the Microstructure and Mechanical Properties of Non-Heat Treated HPDC AlSi10MnMg Foundry Alloy via Incorporation of TiB<sub>2</sub> Particles and Sc

The demand for structural lightweight in a variety of industries, particularly the automobile industry, has driven the development of heat-free die-cast aluminum alloys with excellent properties. Utilizing lightweight materials, such as Al-Si alloys has several benefits, including higher overall performance in automobiles and other industries, increased heat resistance efficiency, decreased emissions, and reduced weight. The purpose of this study is to modify the microstructure and enhance the mechanical properties of high-pressure die-casting (HPDC) AlSi10MnMg foundry alloy by incorporation of TiB2 and Sc without any heat treatment. The results showed that the HPDC process significantly refines the grain structure and AlSiMnFe intermetallic compounds, transforming the eutectic morphology from sharp to rounded, and 93% enhancement in elongation at the optimum content (0.018 wt.%) of TiB2. While the hardness of the alloy was improved by 15.7% with the addition of 0.03wt.% TiB2. TiB2 incorporation refines the grain structure and AlSiMnFe phases, while depressing externally solidified crystals (ESCs). The HPDC process refines Al3Sc phases as well as AlSiMnFe phases while increasing yield strength due to Al3Sc strengthening effects. After 0.5wt.% Sc addition in 0.018wt.% TiB2-AlSi10MnMg alloy, the YS, and EL reached the maximum of 196MPa and 9.93% respectively.

Assessing efficacy of standard impregnation techniques on die-cast aluminum alloys using X-ray micro-CT

Assessing efficacy of standard impregnation techniques on die-cast aluminum alloys using X-ray micro-CT

Data extension-based analysis and application selection of process-composition-properties of die casting aluminum alloy

This research aims to provide a solution to the scarcity and fragmentation of industrial data on die casting aluminum alloys. Quantifying the coupling between die casting process-composition-properties of aluminum alloys through small datasets, is a critical step in predicting part properties and optimizing process selection. To visualize the connections and discuss the effect of the interaction between different parameters on the property, data is fed into a self-organizing mapping model. Whereafter, an innovative data extension method is proposed to predict both yield and tensile strengths with more than 96% accuracy using a small data set. Moreover, two novel methods of multi-parameter combined range selection, the multi-objective optimization based on the agent model and the superimposition of the contour map, are guided by being informed in which region the mechanical properties fall. Finally, the feasibility of application range selection method is verified experimentally. Mapping based on data-driven process-composition-properties relationships and the free combination of application ranges are reliable theoretical solutions which are valuable for practical applications.

Parts repairing and microstructural refinement of high-pressure die cast aluminum alloys through friction stir processing for bulk production

A key challenge in the production of high-grade automotive aluminum components through the High-Pressure Die Casting (HPDC) process is the imperative to minimize imperfection. In addressing this concern, this study utilizes friction stir processing (FSP), a widely recognized intense plastic deformation technique. FSP is applied to systematically alter the microstructure of HPDC Al-4Mg-2Fe, a prominent alloy extensively used in the die-casting sector. By using the pass strategy to incorporate both one-pass and two-pass approaches, the microstructure is selectively altered to establish a defect-free processed zone. The utilization of FSP demonstrates its efficacy in breaking aluminum dendrites and acicular silicon particles, leading to a uniformly dispersed arrangement of equiaxed silicon particles within the aluminum-based matrix. In addition, FSP eradicates porosity and disintegrates needle-like Fe particles, resulting in a more refined and homogeneously distributed structure. Subsequently, the material's mechanical properties processed by FSP were assessed in the longitudinal direction concerning the processing axis and then compared with those of the original base material.The microstructural refinement and reduction in porosity induced by FSP result in a notable enhancement in hardness, with an increase of 23 % after one pass and 37 % after two passes. The substantial improvement in mechanical properties during the FSP process is predominantly attributed to modifications in the morphology, refinement, and dispersion of intermetallic particles within the matrix. This improvement is further complemented by the ultrafine dispersion of casting defects.This study underscores the efficacy of FSP as a valuable tool for modifying microstructures and improving mechanical properties in HPDC Al-4Mg-2Fe alloys. Such advancements align with the lightweighting objectives pursued by the automotive industry.

Research Progress on Thermal Conductivity of High-Pressure Die-Cast Aluminum Alloys

High-pressure die casting (HPDC) has been extensively used to manufacture aluminum alloy heat dissipation components in the fields of vehicles, electronics, and communication. With the increasing demand for HPDC heat dissipation components, the thermal conductivity of die-cast aluminum alloys is paid more attention. In this paper, a comprehensive review of the research progress on the thermal conductivity of HPDC aluminum alloys is provided. First of all, we introduce the general heat transport mechanism in aluminum alloys, including electrical transport and phonon transport. Secondly, we summarize several common die-cast aluminum alloy systems utilized for heat dissipation components, such as an Al–Si alloy system and silicon-free aluminum alloy systems, along with the corresponding composition optimizations for these alloy systems. Thirdly, the effect of processing parameters, which are significant for the HPDC process, on the thermal conductivity of HPDC aluminum alloys is discussed. Moreover, some heat treatment strategies for enhancing the thermal conductivity of die-cast aluminum alloys are briefly discussed. Apart from experimental findings, a range of theoretical models used to calculate the thermal conductivity of die-cast aluminum alloys are also summarized. This review aims to guide the development of new high-thermal-conductivity die-cast aluminum alloys.

Joining aluminum die castings and wrought aluminum by resistance spot welding

Resistance spot welding (RSW) is an economic, robust welding process, which is easy to automate and widely used in automotive industry. In this work, the resistance spot weldability of die-cast aluminum alloys EN AC-AlSi7MnMg, EN AC-AlSi9Mn and EN AC-AlSi10MnMg-T6/T7 to wrought aluminum alloy EN AW-AlSi1MnMg-T6 is investigated when applying the standard welding profile as recommended in VDA 238-401 considering main challenges in welding aluminum die castings, for example, porosity and inhomogenities. Weldability is best for EN AC-AlSi10MnMg-T6/T7, but the results show limited applicability of VDA 238-401 in general, especially for high total sheet thicknesses, because of invalid electrode force favouring spatter formation and weld spot irregularites. Still, all spot welds between die castings and 2 mm wrought aluminum sheets reach the recommended shear tension forces for spot diameter dw of 5·√t (2 mm: 5.95 kN; 3 mm: 8.96 kN; according to DIN EN ISO 18595), although being afflicted with solidification porosity and liquation cracking. Gas porosity is not observed and solidification porosity is only found to be significant for weld spot failure when being located close to the joining level, which is observed at welding depths of approximately 50% into the wrought aluminum sheet. Here, a failure path across the nugget is found. Weld porosity apart from the joining level is less significant and failure path is found along the fusion line between nugget and wrought aluminum. Instead, hardness difference between nugget and HAZ is the main reason for weld spot failure. Although the applied welding current profile is not suited best for RSW of mixed joints between aluminium die castings and wrought aluminium alloys, the results confirm its potential, for example, a significantly reduced gas porosity compared to applied fusion welding processes.

Investigating Thermal and Mechanical Characteristics of Die-Casting Aluminum Alloys: A Comprehensive Investigation via Thermal Analysis

Investigating Thermal and Mechanical Characteristics of Die-Casting Aluminum Alloys: A Comprehensive Investigation via Thermal Analysis

Crevice Corrosion Initiation and Growth of Die-Cast ADC12 Aluminum Alloy

Die-cast ADC12 (Al-3Cu-10Si) aluminum alloy is widely used because of mechanical properties and castability. In atmospheric environments, crevice corrosion sometimes occurs on ADC12; therefore, improvement of corrosion resistance and elucidation of corrosion mechanisms are needed.As-cast specimens of ADC12 were used in this study. Pure Al sheets were used for comparison. The microstructure of ADC12 was composed of α-Al and Al-Si eutectic phases. Intermetallic particles (IMPs) containing Cu existed. IMPs containing Fe also existed. The size of IMPs was around 1 μm.Crevice was made between a polycarbonate nut and bolt, and immersion test was performed in 0.1 M NaCl. After immersion, the dissolution of α-Al was observed inside the crevice. To ascertain the effect of pH on α-Al phase dissolution, immersion test was carried out in 0.1 M HCl and 0.1 M NaCl (pH 10.0) In 0.1 M HCl, α-Al dissolved, and the corrosion morphology was similar to that inside the crevice.

Enhanced toughness and tear resistance of thin-walled High-Pressure Die-Cast aluminum alloys through Friction stir processing

In this study, we investigate the toughness and resistance to tear of thin-wall high-pressure die-cast (HPDC) aluminum alloys in two different orientations following the implementation of friction stir processing (FSP). The FSP technique was applied to two different HPDC Al-Si alloys: the recyclable-grade, high iron, A380 alloy and the premium-quality, low iron, Aural-5 alloy. Our findings reveal significant tear resistance and strength enhancements for both alloys after FSP modification. Specifically, FSPed A380 alloy requires 126% higher energy to tear, and it has 49% higher tear strength than the HPDC counterpart. Similarly, the tear energy and tear strength of the Aural-5 alloy witness enhancements of 69% and 21%, respectively. These findings emphasize the capability of FSP to improve the toughness of HPDC aluminum alloys, creating new possibilities for preventing cracks in a variety of engineering applications.

Research on composition-process-property prediction of die casting Al alloys via combining feature creation and attention mechanisms

In industrial applications, the mechanical properties of die casting Al alloy parts are influenced by a combination of material composition and forming process. This study establishes a performance data-driven framework that takes into account balanced weights of alloy compositions and process parameters. First, a compositional coefficient normalization method is proposed, in which the electronegativity, thermal, and physical descriptors are dot-multiplied into the coefficient matrix to build alloy factors for coupled compositional information. Higher prediction accuracy and lower risk of overfitting validate the feasibility of the method. Subsequently, to improve the performance of machine learning (ML) model for prediction of mechanical properties, a feature engineering method embedded in attention mechanism is used. The experimental results with high accuracy confirm the ability of the ML model to reproduce the relationships between alloy properties and balance their sensitivities. Finally, contour plots of the characterized parameters are constructed for predicting mechanical property intervals and guiding parameter design. This study innovatively applies the normalization method to the field of die casting aluminum alloy feature optimization. And combined with the attention mechanism to improve the prediction accuracy between material features and target properties, which may also be extended to other alloys.

Ductile fracture prediction of HPDC aluminum alloy based on a shear-modified GTN damage model

In this paper, we investigate how the shear-modified Gurson-Tvergaard-Needleman (GTN) model can be used to reveal the effect of manufacturing-process-induced porosity on the scatter of ductile fracture properties of a high-pressure die-casting aluminum alloy. The GTN model exhibits great advantages in predicting the variation of failure strain/displacement by altering the initial void volume fraction (f0), compared with uncoupled ductile damage models. For a specific metallic material, one unique set of model parameters is usually determined from experiments, which leads to the fact that only a deterministic failure strain/displacement can be obtained under a fixed porosity. To overcome this shortcoming of the shear-modified GTN model, a novel parameter calibration scheme is proposed and validated in the present study. Following the physical background of the GTN model, the twelve material parameters of the shear-modified GTN model have been determined based on a combination of macroscopic mechanical tests covering a wide range of stress states and micromechanics-based unit cell simulations. Different from the existing calibration strategies, the simulation results of unit cells embedded with a spherical void have revealed a mutual dependence between the f0 and critical void volume fraction (fc). By conducting interrupted shear tests, the evolution of secondary nucleated void volume fraction was identified according to the statistical results of the fractured brittle silicon particles. The remaining parameters have been further iteratively determined. In the end, the effectiveness of the proposed parameter determination approach is confirmed based on the accurate prediction of stochastic ductile failure properties (both the global failure displacements and the local failure patterns) in different fracture tests. Given the proposed parameters identification strategy, the GTN material models have been enriched to predict the ductile failure behavior of metallic materials, which possess relatively high porosities and more pronounced scattering in failure properties.

Detection of Porosity in Impregnated Die-Cast Aluminum Alloy Piece by Metallography and Computer Tomography

The porosity of die-cast aluminum alloys is a determining factor for the quality of the product. In this paper, we studied the porosity of a selected part of a die-cast AlSi9Cu3(Fe) compressor part by computer tomography and metallography. In the case of this part, the achievable resolution by CT, a non-destructive testing method, was 30 μm—this method could not detect smaller cavities. Based on metallographic analysis, the percentage of defects larger than 30 μm ranges from 10 to 30% of the total number of defects, which represents 75–95% of the defective area (area ratio). Impregnation with methacrylate resin (used to seal cavities to prevent leakage) can be detected with UV-illuminated optical microscopic examination on metallographically prepared specimens. As confirmed by scanning electron microscopy, partial filling and partial impregnation can occur in a system of shrinkage cavities.

Simulation of Fracture Performance of Die-Cast A356 Aluminum Alloy Based on Modified Mohr–Coulomb Model

The fracture performance and damage prediction of die-cast materials are critical to guarantee the safe application of die-cast structural components in lightweight vehicles. Monotonic loading experiments were conducted on different shapes of die-cast aluminum alloy A356 specimens. Finite element simulation models of the A356 monotonic loading experiments were established, and the stress state of the specimens during the loading process was analyzed. The Modified Mohr–Coulomb (MMC) failure model of A356 was fitted by the failure strain under different stress states. Finally, the established MMC failure model was verified by a uniaxial compression experiment and bending experiment. The results show that the MMC failure model can be applied to the prediction of the fracture behavior of A356.

Understanding conformal cooling in the diecasting of aluminum alloys

Heat transfer and stress distribution are studied using computational fluid dynamic and structural simulation for a conformal cooling die insert made of Maraging M300 steel by selective laser melting. The phase transformation of cooling water is studied to understand the cooling effects and stress concentration on die life. The results of simulation are validated in production. The failure of the die insert has been revealed a result of enhanced stress concentration and corrosion directly related to the formation of vapor in the conformal cooling channel.

Influence of pores on the lifetime of die cast aluminium alloys studied by fracture mechanics and X-ray computed tomography

Pores and other defects play a crucial role in aluminium die cast alloys. They critically affect the fatigue properties and lifespan of components. The application of fracture mechanics methods is a cornerstone in the calculation of high cycle fatigue properties of such components. In recent research failure behaviour and internal structure of defects are analysed and predicted based on X-ray computed tomography scans (CT) and machine vision integrated into the simulation models. Here, we present the analysis of defects of the die cast aluminium alloy EN-AC46200. In the first step, we use CT scans to analyse pores and defect structures. Afterwards, the CT scans are evaluated for pores and defects using modern 3d image analysis software. Additionally, the samples are tested by high cycle fatigue until failure. To determine the stress intensity, the pore analysis is combined with the help of machine vision. Furthermore, a novel clustering method based on 3d volume data is proposed to predict critical regions of the samples. We show that by this approach we can augment the fracture mechanics of the defects and identify critical pores in combination with stress hot spots in the aluminium die cast alloy.