Powder Metallurgy Aluminum Research Articles

An integrated experimental and analytical approach on mechanical characterization of advanced powder metallurgy aluminium metal matrix composites reinforced with different particulates

Over the last few decades, ‘Discontinuously Reinforced Particulate Composites (DRPCs)’ are a popular class of composite materials with considerable challenge in processing, characterization and machinability because of their increased strength-weight ratio, stiffness, specific strength and oxidization when compared to various metals and their alloys. This paper discusses experimental and numerical investigation on mechanical characteristics of aluminum metal matrix reinforced with various reinforcement particulates such as silicon carbide, aluminium oxide, and zirconium oxide, compaction pressure (kN) and hold time (s) based on Design of Experiments (DOE) and Finite Element Analysis. Initially this paper discusses the process optimization of Aluminum Matrix reinforced with different particulates experimentally to identify the favourable processing conditions by varying reinforcement materials, compaction pressure (kN) and hold time (s) based on TDOE (Taguchi’s Design of Experiments). Further, this paper concentrates to determine ‘maximum principal stress, equivalent elastic strain and equivalent (von-mises) stress’ based on Finite Element Analysis (ANSYS Workbench-2023R1). The results of the experimentation showed that the highest hardness values were achieved with ZrO2 reinforcement material. Increasing the compaction pressure from 8 to 12 kN resulted in a slight decrease in surface roughness and porosity. Higher compaction pressures have assumed to facilitate better particle distribution and improved interfacial bonding, leading to smoother surfaces and lower void content. The simulation results showed that the maximum principal stress achieved were (2235.8 MPa) SiC, (3444.4 MPa) Al2O3, and (3582.5 MPa) ZrO2. The equivalent elastic strain achieved was (0.2488) SiC, (0.2421) Al2O3 and (0.262) ZrO2. The equivalent (Von Mises) stress achieved was (28751 MPa) for SiC, (24880 MPa) for ZrO2 and (26972 MPa) for Al2O3. This experimentation and simulation demonstrated that the PM process can be used to fabricate DRAMMC with different reinforcement particulates. The understanding gained experimentally and analytically from this research can be applied for future processing of Aluminum Matrix Reinforced with different particulates.

Effect of copper introduction on the properties of micro-arc oxidation coating on powder metallurgy aluminum disk

Powder metallurgy (PM) is a process technology utilizing metals as raw materials that are shaped and sintered to create metallic materials. Micro-arc Oxidation (MAO) is a surface modification technique that improves the surface properties of metals by forming a dense oxide coating on the metal surface. In this study, aluminum‑copper alloys were prepared by introducing copper to PM aluminum disk, and the alloys were treated with MAO. During the PM process, Cu atoms diffuse into the Al particles, filling the gaps in the Al particles and improving the interface bonding strength of the particles. The CuAl2 phase is also generated, which improves the mechanical properties of the alloy. During the MAO process, the addition of Cu filled up the pore defects of the PM Al disk, and a complete and dense oxide coating was formed on the surface of the alloy. The MAO coating was characterized by scanning electron microscopy and X-ray diffraction. The mechanical strength of the alloy was evaluated by metal bending tests. The wear resistance of the coating was evaluated by tribological tests and the wear marks after friction were characterized by metallographic microscopy and energy dispersive spectroscopy. The hardness of coating was evaluated by microhardness tester. The corrosion resistance of the coating was evaluated by electrochemical corrosion tests. The test results show that the substrate after the introduction of Cu by PM and treated by MAO has high strength, high hardness, low coefficient of friction, high wear resistance and high corrosion resistance. It effectively improves the mechanical properties of the alloy, improves the performance of the MAO coating, and improves the service life and application range of the metal.

Grain Size Evaluation of Selectively Heated Sintered PM Preforms under Cold Compression

Abstract The mechanical qualities of the materials determine the final product’s performance in engineering applications, and the analysis of material grain size could change these attributes. Controlling grain size is critical in the metal forming process for obtaining good mechanical characteristics, which improves the final component’s performance. The purpose of this research is to determine the impact of selective heating (SH) on the microstructure of sintered powder metallurgy aluminum- and titanium-based preforms for various titanium weight fractions (2–6 %) and starting relative densities (80–90 %). Cold upsetting tests of sintered aluminum-titanium workpieces were carried out in a hydraulic press for several ranges of SH (100°C–250°C). The microstructure of aluminum-titanium specimens was examined using an optical microscope, and the intercept line approach was employed to calculate the average grain size (AGS). Because of dynamic recrystallization and grain development, the AGS of aluminum-titanium preforms is found to increase as the SH temperature rises.

Advancements in microstructure, texture characterization, and mechanical properties of powder metallurgy Al-Si-Mg-Fe alloy for engineering applications

Metal powder metallurgy (PM) is widely utilized in the tool and automotive industries due to its near-net forming advantages. While PM aluminum alloys have been explored in numerous studies, their practical engineering applications are still limited. Thus, this research delves into the nuanced aspects of PM Al-Si-Mg-Fe alloy. By employing hot-rolled dynamic recrystallization to control the metallurgical texture and introducing T6 treatment to refine the microstructure. These optimizations aim to enhance the properties of PM aluminum alloy materials. Results revealed that grain coarsening in the PM Al-Si-Mg-Fe alloy hampers the grain boundary strengthening effects, thus limiting the strength. Moreover, the solid-solution treatment applied to the PM specimens efficiently disperses silicon particles within the matrix, preventing the aggregation of silicon particles and the associated brittle effect caused by interface peeling. By implementing a three-stage process, sintering-rolling-T6 treatment, the rolled-T6 exhibited impressive tensile strength (291 MPa) and ductility (17 %), highlighting the excellent engineering applicability of PM Al-alloys. TEM analysis confirmed the presence of nanoprecipitation Al3Mg and Al9Fe2 hard components within the matrix, contributing to the strength enhancement. These findings not only represent a significant milestone in the advancement but also provide valuable references for engineering applications in the field of PM Al-alloys.

Microstructure and mechanical properties of powder metallurgy 2024 aluminum alloy during cold rolling

To improve the low compactness and limited size of powder metallurgy (P/M) aluminum alloy materials, cold rolling deformation on P/M aluminum alloy was carried out in this work. And the microstructure and mechanical properties of P/M aluminum alloy during cold rolling were investigated from multi-dimensional and multi-scale perspectives. The results indicate that the microstructure gradually evolved from the original equiaxial structure to the fiber structure after cold rolling. Also, the grain size decreased with an increase in cumulative reductions. When the cumulative reduction was increased from 0 to 80%, the relative density and tensile strength of the samples increased from 98.31% to 221.94 MPa to 99.04% and 302.88 MPa, respectively. On this basis, the synergetic effect of microstructure densification and deformation strengthening of the P/M 2024 Al alloy during cold rolling was investigated. The improved mechanical properties mainly resulted from the combined effects of the increased microstructural compactness and deformation strengthening.

Sustainable Production of Powder Metallurgy Aluminum Foams Sintered by Concentrated Solar Energy

Porous aluminum foams were successfully fabricated following the space-holder powder metallurgy method with a solar sintering stage. Al foams with porosities of 50, 60, and 70 vol.% were sintered in a low-cost Fresnel lens. Green parts were prepared using aluminum powder as the main metallic material and saccharose as a soluble space-holder. The dissolution stage was designed for each foam and required longer periods of time, between 8 and 32 h, as the design porosity increased. Brown parts were fully sintered by concentrated solar energy at a lower temperature (500 °C) and for shorter times (12–20 min) than those required by conventional sintering techniques (640 °C, ~9 h). The evaluation of density and the characterization of pore size and distribution in the sintered foams was carried out. All obtained foams were stable and presented a homogeneously distributed porosity, very close to the design porosity, with differences lower than 2.1 vol.%, and with approximately half being characterized as open porosity. Moreover, the solar sintered foams presented a high quality, and similar or even greater mechanical properties (such as compressive strength and impact energy absorption) than those achieved by conventional techniques. Foams with 50 vol.% of porosity exhibited the best mechanical behavior, in terms of impact-energy absorption (24.42 MJ/m3) and compressive strength (27.4 MPa).

Microstructure and tensile properties of aluminum powder metallurgy alloy prepared by a novel low-pressure sintering

This paper proposed a novel low-pressure sintering process contraposing to characteristics of pre-alloyed aluminum powders and analyzed its feasibility. The low pressure was set to 0.1 MPa in this study. Meanwhile, 0 MPa and 10 MPa were set as control group. With gas-atomized 2024 aluminum powders as raw material, the microstructure and tensile properties of specimens sintered under three orders of magnitude of pressure (0 MPa, 0.1 MPa and 10 MPa) at two representative temperatures (525 °C and 575 °C) were compared. The results showed that it was difficult for pressureless sintering (0 MPa) to densify pre-alloyed aluminum powders, but low-pressure sintering could. As the liquid phase formed at supersolidus temperature was squeezed out, the loss of alloying elements such as Cu and Mg, which would play an important role in subsequent heat treatment, during low-pressure sintering was apparently less than that of 10 MPa. The density of aluminum sintered under 0.1 MPa at 575 °C was 2.732 g/cm3 and the ultimate tensile strength was 228.16 MPa with ductility of 12 %, which achieved a good balance of plasticity and strength. These findings will bring new insights to the industrialization of aluminum powder metallurgy (APM).

A Micromechanics Analysis for Creep of Powder Metallurgy Aluminum Alloys with Continuous Precipitation

In this study, a micromechanics framework considering both interface diffusion and matrix creep is proposed to analyze the creep behavior of PM alloys. Based on the mean-field micromechanics theory, the creep strain rate induced by interface diffusion in the particulate composite under uniaxial loading is derived. The creep strain is introduced as an eigenstrain into the inclusion, whose rate is expressed in the tensor-form with three non-zero components and naturally satisfies incompressibility. An incremental analysis procedure is employed to model the creep behavior of particulate composites. The aluminum alloy is treated as a composite material, with precipitated particles as the reinforcements. We then adopt the proposed micromechanics approach to study the creep behavior of the powder metallurgy aluminum alloy with continuous precipitation, accounting for both the creep of matrix and the creep induced by interfacial diffusion along the precipitate/matrix interface. The predicted creep curves agree well with experimental results and the explanation for the creep phenomenon has never been proposed before. We have also derived the minimum or steady-state creep rate of the alloy by the micromechanics approach, which turns out to be similar to the expression of improved power-law creep with a threshold stress.

Investigation of PCTIG, CCTIG and MMA Welding on Powder Metallurgy Aluminium Specimen Processed through Equi-Channel Angular Pressing (ECAP)

Investigation of PCTIG, CCTIG and MMA Welding on Powder Metallurgy Aluminium Specimen Processed through Equi-Channel Angular Pressing (ECAP)

Hot Extrusion of a Commercial Aluminum Powder Metallurgy Metal Matrix Composite Material

Abstract Sintered preforms made of an aluminum powder metallurgy (PM) 2000 series metal matrix composite designed for press-and-sinter applications were forward extruded at 450°C under displacement rates of 254 mm/min and 2,032 mm/min. The material was highly responsive to extrusion under these conditions and was readily formed into products that included 10-mm and 15-mm solid round bars as well as C-channel and round tubing profiles, wherein extrusion ratios ranged from 11:1 to 76:1. Significant metallurgical improvements were also observed in the seemingly defect-free products. These included gains in tensile yield strength (10 %), ultimate tensile strength (20 %), and tensile ductility (400 %) when compared to the nonextruded T6 counterpart. Such enhancements were attributed to the attenuation of full theoretical density, disruption of the residual oxide network, and the development of a partial duplex fiber texture with strong <111> and moderate <100> fiber components within the extruded PM products.

New development of powder metallurgy in automotive industry

The driving force for using powder metallurgy (PM) mostly relies on its near net-shape ability and cost-performance ratio. The automotive application is a main market of PM industry, requiring parts with competitive mechanical or functional performance in a mass production scale. As the automobile technology transforms from traditional internal combustion engine vehicles to new energy vehicles, PM technology is undergoing significant changes in manufacturing and materials development. This review outlines the challenges and opportunities generated by the changes in the automotive technology for PM. Low-cost, high-performance and light-weight are critical aspects for future PM materials development. Therefore, the studies on PM lean-alloyed steel, aluminum alloys, and titanium alloy materials were reviewed. In addition, PM soft magnetic composite applied to new energy vehicles was discussed. Then new opportunities for advanced processing, such as metal injection molding (MIM) and additive manufacturing (AM), in automotive industry were stated. In general, the change in automotive industry raises sufficient development space for PM. While, emerging technologies require more preeminent PM materials. Iron-based parts are still the main PM products due to their mechanical performance and low cost. MIM will occupy the growing market of highly flexible and complex parts. AM opens a door for fast prototyping, great flexibility and customizing at low cost, driving weight and assembling reduction.

A microstructural and mechanical property investigation of a hot upset forged 2xxx series aluminum powder metallurgy alloy reinforced with AlN

Abstract Metal-matrix composites (MMC) of a 2000-series aluminum alloy coupled with AlN were fabricated through a commercially-relevant aluminum powder metallurgy (APM) approach. Cylindrical preforms containing 0–5 vol% AlN were produced to investigate the mechanical properties and microstructure evolution through hot upset forging. Specimen were deformed to a maximum strain of 0.15–1.55 mm/mm at rates of 0.1–1.0 s−1. TEM observations of forged products indicated the Al–AlN interfaces were free of defects and of high quality. Near-full (>99.5% theoretical) densities were observed at 1.40 mm/mm. At this strain, a substantial increase in all tensile properties was observed. An elastic modulus of 77 GPa was realized in a forged product with 5% AlN, accompanied by a 0.2% offset yield strength of 325 MPa and a UTS of at least 400 MPa. Versus an undeformed sample, forged MMC’s exhibited up to a five-fold increase in tensile ductility. Likewise, improvements of up to 98 MPa (57%) in fatigue strength were recorded. Mechanical gains were a result of densification and residual oxide disruption, as well as the enhanced dispersion of the AlN phase.

Mechanical behavior of steel and aluminum foams at elevated temperatures. Local buckling based approach toward understanding of the material system behavior

The objective of this study is to understand and quantify the thermo-mechanical behavior of hollow sphere (HS) steel and powder metallurgy (PM) aluminum foams over a broad range of elevated temperatures. The behavior of both the HS steel and PM aluminum foam is tested under compressive loading at ambient temperature (24 ∘C) and elevated temperatures of 100 ∘C, 150 ∘C, 200 ∘C, 300 ∘C, 400 ∘C, 550 ∘C and 700 ∘C, and results for the two foams are compared by their rates of degradation in mechanical properties. To link the cell geometry and base metal properties with the global mechanical performance, the experimental work is underpinned by a computational micro-model, consisting of an assembly of hollow spheres. The computational model shows that plastic buckling of cells with progressive plasticity of the contact area is the key local failure mechanism. As expected, due to the plastic buckling of the unit cells, thermal degradations of the tested metallic foams follow similar trends as does the yield stress of their bulk metals. The HS steel foam exhibits only minor elevated-temperature-induced degradation in stiffness and strength at or below 400 ∘C, while still maintaining 69% of its compressive strength at 550 ∘C. Comparatively, the PM aluminum foam begins degrading at an elevated temperature of only 150 ∘C. Interestingly, the HS steel foam oxidized between 300 ∘C and 400 ∘C, resulting in corresponding increases in the quasi-elastic modulus of elasticity. Future work might explore how to take advantage of oxidation reactions at the surfaces of the cells in the design of components using HS steel foams. Our computational study also revealed a possible new regime of cellular structures made up of ultra-thin-walled spherical cells that are predicted to fall within the elastic buckling regime at the local level. Thus, their deformations would be reversible even under high strains and their thermal behavior would be only controlled by thermal deterioration in the elastic constants, rather than plasticity parameters such as the yield stress.

Experimental Examination of Process Parameters During Fabrication and Machining of Powder Metallurgy Aluminum Component

The present study aims at investigating the effect of process characteristics during fabrication and machining of powder metallurgy (PM) Aluminium cylindrical components. The application of the machining process as an alternate manufacturing process to fabricate the PM Aluminium components for industrial use with desired shape and size is explored. The PM Aluminium cylindrical components were fabricated by compacting the Aluminium metal powder within the compaction dies under various values of compaction load, sintering temperature and sintering time. These PM components were then machined under different standard cutting velocity and tangential cutting velocity, surface roughness data were analyzed. After the investigation it was concluded that, higher values of compaction load, sintering time and sintering temperature leads to higher values of relative density and relative hardness of the sintered Aluminum component. Again from machining results it can be stated that, higher values of fabricating parameters have a higher significance on performance parameters.

Different Formation Routes of Pore Structure in Aluminum Powder Metallurgy Alloy.

In powder metallurgy (PM), severe plastic deformation (SPD) is a well-known technological solution to achieve interesting properties. However, the occurrence of pores in the final product may limit these properties. Also, for a given type of microstructure, the stereometric parameters of the pore structures, such as shape (represented by Aspect and Dcircle) and distribution (fshape, and fcircle), decisively affect the final properties. The influence of different processing routes (pressing, sintering and equal channel angular pressing (ECAP)) on pore structures in an aluminum PM alloy is discussed. The nature of porosity, porosity evolution and its behavior is explored. The correlation between pore size and morphology is also considered. The final pore structure parameters (Aspect, Dcircle, fshape, and fcircle) of studied aluminum alloys produced by different processing routes depends on the different formation routes.

Age Hardening of Extruded AA 6005A Aluminium Alloy Powders.

Pre-alloyed micron-sized 6005A Al alloy (AA 6005A) powders, with a Mg/Si atomic ratio of 0.75, obtained by high pressure inert gas atomization were consolidated by uniaxial cold pressing at 200 MPa into cylindrical Al containers and hot extruded at 450, 480 and 500 °C with an extrusion rate of 7:1, followed by artificial T6 precipitation hardening. Ageing conditions were varied between 170 °C and 190 °C and times of 6, 7 and 8 h. The microstructure of the extruded profiles was analysed using X-Ray diffractometry (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) was used to study the possible phase transformations. After our results, the peak-aging hardness condition was achieved at 180 °C for 6 h. Mechanical properties of the powder metallurgy (P/M) aluminium alloys consolidated by hot extrusion were superior to those of the extruded profiles of wrought alloy using conventional ingot metallurgy (I/M) billets. AA 6005A wrought P/M alloy via T6 heat treatment shown yield stress of 317 MPa and elongation of 21% at the extrusion pre-heating temperature of 500 °C.

Effects of process variables on the mechanical and physical properties of an Al–Cu–Mg powder metallurgy alloy

The objective of this research was to analyze the effect sizing and heat treatment had on the properties of a 2xxx series aluminum powder metallurgy alloy. Al–2.3Cu–1.5Mg–0.5Sn was used for experimental work. Natural and artificial aging was studied, as well as various sizing pressures and delay times between process steps (ex. sintering and sizing). It was determined that sizing increased tensile yield strength but decreased tensile ductility and fatigue resistance. Yield strength increased as much as 32% when sized at 400 MPa, whereas ductility and fatigue strength were reduced by up to 51% and 31%, respectively. Delay time between sintering and sizing (T2 samples) did not appear to significantly impact mechanical properties. Through differential scanning calorimetry it was determined that sizing impacted the precipitation of S-type precipitates. It was inferred that there was a preferential tendency for S1-type precipitates to form in sized samples, suppressing full aging to S2-type.

Powder metallurgical processing of a 2xxx series aluminum powder metallurgy metal alloy reinforced with AlN particulate additions

Two AlN powders were admixed with a commercially-relevant press-and-sinter aluminum alloy, differentiated by their mean particle sizes of 3.0 and 12 μm. The effects on powder characteristics and mechanical properties were of primary interest and were compared to nonreinforced compacts. Ceramic additions affected the behavior of the alloy in the powdered, green and sintered state. AlN additions promoted gains in green strength but negatively affected sinterability in some instances although effects were marginal when coarse or fine AlN powder additions were limited to 5 vol% and 2 vol%, respectively. Decreased densities manifested as marginal decreases in yield strength, UTS and fatigue properties. For a fixed AlN concentration, alloys containing D50 = 12 μm or D50 = 3 μm AlN exhibited comparable mechanical properties. Above 5%, the coarser particulate maintained a higher sinterability and superior mechanical properties. Dynamic elastic modulus measurements of 73.0 and 74.3 GPa were measured for compacts with 2 and 5 vol% of coarse AlN particulate. AlN additions did not significantly influence the fatigue survival stress.

Microstructural evolution of a forged 2XXX series aluminum powder metallurgy alloy

The microstructural response to hot upset forging was studied for a commercially relevant 2000-series aluminum powder metallurgy alloy. Sufficiently large specimens were produced such that the tensile property development was recorded for true compressive forging strains 0 mm/mm to 1.55 mm/mm. Full theoretical density values were obtained and up to a four-fold improvement in tensile ductility was observed. The tensile strength of a sintered-T6 component was measured at 357 MPa, while forging to 1.40 mm/mm increased that to 418 MPa. Microstructural reinforcement was found to be predominantly S-phase precipitates. Prior particle boundaries (PPB) of an unforged specimen were found to be continuously decorated with MgO and Mg2Sn crystallites. Such boundaries in hot forged specimen were discretized into clusters, producing regions of PPB devoid of oxides or other secondary phases. Improvements to mechanical properties were largely attributed to this effect.

Synthesis and friction properties of a multifunctional diamond-containing ceramic material

Abstract The paper investigates the fundamentals of the technology of forming multifunctional composite diamond-containing materials with a ceramic matrix of an aluminum oxide. It shows the results of comparative tests of triboengineering properties of the obtained material. The developed technology for creating a billet for a diamond-containing composite ceramic material uses powder metallurgy (aluminum powder and dispersed diamonds). The paper determines optimal modes to form a billet. A sample of a composite mixture has been modified by microarc oxidation. It had a hardened layer of a ceramic matrix on its surface, and a dispersed diamond evenly enclosed in it. There is a description of features of the microarc oxidation technological process of a part from a sintered diamond-aluminum mixture compared with aluminum alloys. It is determined that the thickness of the formed ceramic layer is several times higher compared with the parts made of non-porous aluminum alloys. Moreover, the alkali concentration in the electrolyte and the relative density of a sintered billet have the greatest effect. There are two types of ceramic diamond-containing materials based on the proposed technology. They are: antifriction construction materials for sliding friction units and tool materials for abrasive processing. Triboengineering tests of materials with a small grain size of diamonds revealed their good antifriction properties even without lubricating with liquid materials. It has been established that an abrasive tool made from a material with a high grain size of diamonds has higher wear resistance and productivity compared with traditional abrasive materials.