Al-Si Piston Alloy Research Articles

Chemical composition of the Ni-containing intermetallic phases in the multicomponent Al alloys

In this study an effect of the alloying elements content and cooling rate on the morphology and chemical composition of the Ni-containing intermetallic phases in the Al–Si piston alloys has been examined. Compiled procedure of the selection and classification of the point X-ray microanalysis results allowed to estimate homogeneity range of the particular classes of the Ni-containing intermetallic phases occurred in the AlSi12MCuNiMg and AlSi21CuNi alloys. Replacement range: Cu→Ni in the Al3(CuNi)2 phase, and Fe→Ni or Cu→Fe in the Al9(FeNi)2 phase has been estimated and compared to that reported previously. The obtained results showed that chemical composition of the Ni-containing microstructure constituents locally reflected the sequence of precipitation processes on the alloy solidification path. The process of the formation of the Ni-containing intermetallic phases in form of terminal solid solutions of alloying elements in the crystal structure of the base phase through series of both peritectic and eutectic reactions has been discussed.

Prediction of Mechanical Properties of Nano-Composites Using Vibration Modal Analysis: Application to Aluminum Piston Alloys

Abstract In this work, aluminum piston alloy-based nano-composites of high strength and ductility with large damping capacity were produced. Ni particles and Al2O3 particles were used as reinforcing agents to produce three nano-composites by adding three mixtures of these particles to the melt of Al-Si piston alloy at 700°C and application of stirring and squeeze casting. In addition, three micro-composites were produced by adding Ni particles of different percentages to the melt of the same matrix alloy and application of mechanical stirring and squeeze casting with the same conditions. The microstructures of the different materials were investigated using optical and scanning electron microscopes. Energy-dispersive x-ray analysis was carried out to analyze the elements of the reinforcing and matrix materials. Ultimate tensile strengths and engineering strains of the unreinforced and reinforced materials were evaluated by carrying out tension tests at room temperature. Modal tests were also carried out to evaluate the dynamic characteristics: natural frequency and damping ratio. The tests showed that the ultimate tensile strengths, ductility, and damping capacity of these composites were improved by the increase of both Ni and/or Al2O3 contents. A dynamic life indicator (damping ratio divided by natural frequency) is calculated for each material and showed a significant increase with the increase of nano-particles and/or micro-particles. By carrying out the experiments at different conditions, the mechanical properties, modal characteristics (such as natural frequency and damping ratio), and life indicator can be correlated. By constructing relationships between these properties and dynamic characteristics, the vibration modal analysis can be used for prediction of these properties and characteristics non-destructively.

Optimisation of cast pistons made of Al–Si piston alloy

In this paper, the advantages of applying software packages for the optimisation of the relevant technological parameters of casting and their implementation and control in production processes using the example of a cast piston are presented. The micro- and macrostructural characteristics of two different modes of solidification are given. In previous studies, possible phases in the microstructure of an aluminium alloy piston were identified, and their influences on the physical, chemical and mechanical properties are well known. The aim of this study is to obtain piston alloys with the desired mechanical and physical properties in the appropriate sections by combination of specific phases (share and distribution stages, the optimal size of primary silicon crystals, grain size, etc.) based on modern techniques.

Morphological evolution of ZrAlSi phase and its impact on the elevated-temperature properties of Al–Si piston alloy

It is investigated that the morphologies of ZrAlSi phase in Al–18Si–xZr alloys will evolve from flake-like to block-like with increasing Zr content and the precipitation of the ZrAlSi intermetallic decreases the volume fraction of primary Si phase. The effect of flake-like and block-like ZrAlSi phase on the microstructure and elevated-temperature mechanical properties of an Al–Si multicomponent piston alloy was also investigated. It was found that flake-like ZrAlSi particles lead to a decrease of 7.28%, 3.23% and 8.85% for the elevated-temperature tensile strength, elongation and yield strength of the piston alloy, respectively, whereas block-like particles cause an increase of 15.82%, 12.94% and 14.75%, respectively. Meanwhile, the linear expansion is almost unaffected.

Effects of Ce, Mn, Cr on the Microstructure and Properties of High-Iron Eutectic Al-Si Piston Alloy

The paper discussed the effects of Ce, Mn, Cr on the microstructure and properties of high-iron eutectic Al-Si piston alloy using orthogonal design. It has been found that Mn and Cr improved the morphology of β phase (Al9FeSi3), becoming the Fe phase that consists of Mn and Cr; Rare earths Ce has a strong effect on refinement of the eutectic silicon. At a high mass fraction of Ce, Ce enter Fe phase that contains Mn and Ce, which improves its morphology greatly and decreases the size of Fe phase, and is able to replace the position of Ni, becoming high-temperature Al-Ni-Cu-Ce phase. The best additions of Ce, Fe, Mn, Cr would be 0.8%, 1.0%, 0.4% and 0.1% respectively and the tensile strength under room temperature (25°C) and high temperature(300°C) would reach 270.3MPa and 136.7MPa respectively, which fully meet the requirements of the use of novel the piston high temperature load.

Effect of Roughness of Hypo-and Hyper-Eutectic Al-Si Piston Alloy on Wear Characteristics under Lubrication

The tribological behavior of tow AlSi alloys under the influence of surface roughness average was investigated for the present study. The silicon content of these alloys ranged 10 and 16-wt% Si, and includes hypoeutectic 383 Al alloys and hypereutectic 390 Al alloys. Various surface roughness averages (Ra) of different degrees were verified as well as three different loads 10, 20 and 30 N, speeds 200, 300 and 400 rpm and relative humidity 75%. Different surface preparation techniques result in different Ra values from (0.2and 4) ± 0.05 um. Surfaces were analyzed through scanning electron microscopy and X-ray dispersive analyses. A pin on-disc apparatus was used for testing in lubrication sliding wear. It was noted that the weighted and volumetric wear rate decreases the degree of roughness and the friction coefficient is a function of the stability state. Wear rate is decreased and the transition from high to low wear increases with an increase in the average surface roughness. It was found that, after the sliding velocity, there was an increase in wear of Al-Si with increasing load, using a scanning electron microscope to study the wear mechanisms. At high speeds, The results of mechanical properties of aluminumsilicon alloys were finally correlated with the amount of silicon in aluminum and secondary processing technique.

Effect of Fiber Volume Fraction on Low Cycle Fatigue Behavior of Al<sub>2</sub>O<sub>3f</sub>/Al-Si Composites

The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

Effect of Fiber Volume Fraction on Low Cycle Fatigue Behavior of Al<sub>2</sub>O<sub>3f</sub>/Al-Si Composites

The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

Double-stage hardening behavior and fracture characteristics of a heavily alloyed Al–Si piston alloy during low-cycle fatigue loading

Low-cycle fatigue tests were performed in an Al–Si piston alloy to manifest its remarkable double-stage hardening behavior and fracture characteristics. The first hardening was related to the interaction between the dislocations and the fine dispersive precipitates, and the second hardening was mainly caused by the dislocation/dislocation interaction. The fatigue fracture crack usually initiated from the large intermetallic colony which was close to the surface of specimen. The debonded Al–Si eutectic region and intermetallics provided a weak path for the crack propagation. The presence of intermetallics had a close relationship with the double-stage hardening behavior and brittle fracture characteristic at room temperature. A fatigue fracture model was comparatively put forward for the heavily alloyed Al–Si piston alloy to describe its fracture process in detail.

Unique cyclic deformation behavior of a heavily alloyed Al–Si piston alloy at different temperatures

The cyclic deformation behavior of a near-eutectic Al–Si piston alloy with a variety of alloying elements is investigated. Due to the distinctive microstructure, the alloy exhibited various cyclic deformation characteristics at different temperatures. Unique double-stage cyclic hardening occurred at room temperature, while the first hardening was mainly caused by the interaction between the dislocations and the finely dispersive precipitates, and the dislocation/dislocation interaction resulted in the second hardening. At elevated temperatures (200°C and 350°C), the alloy mainly presented cyclic softening because of the fact that the thermally activated dislocations could bypass or shear the obstructive precipitates.

Effect of Intermetallics on the Low Cyclic Fatigue Crack Growth Behavior of a Heavily Alloyed Al-Si Piston Alloy

This paper focuses on a typical automotive piston material to characterize its fractographic appearance after low cyclic fatigue test. The fatigue fracture of this heavily alloyed Al-Si alloy takes place in a brittle manner. The crack nucleated from a large intermetallic colony close to the specimen surface. When the crack encountered the intermetallics, it might progress along the interface among the intermetallics or the interface between the intermetallics and the eutectic. The debonded Al-Si eutectic region and intermetallics provided a weak material path for the crack propagation. A fatigue fracture mechanism in the heavily alloyed Al-Si alloy is elucidated.

Evolution, microhardness of ZrAlSi intermetallic and its impact on the elevated-temperature properties in Al–Si alloys

The influence of Si addition on the microstructures and properties of ZrAlSi intermetallics in Al–xSi–2Zr alloys was investigated. With Si addition increasing from 3wt.% to 60%, ZrAlSi evolves from Zr(Al1−mSim)3 (0.10≤m≤0.21) to Zr(AlnSi1−n)2 (0.05≤n≤0.15), the content of Si in ZrAlSi and microhardness of the intermetallics increase synchronously. Besides, all the ZrAlSi intermetallics exhibit flake-like morphology. The effect of Zr addition and precipitation of ZrAlSi intermetallics on the elevated-temperature properties of an Al–Si piston alloy was investigated, and the tensile strength is increased by 3.8% with 0.11% Zr and decreased by 5.0% with 0.46% Zr addition, while the elongation and yield strength are increased by 13.0% and 6.9% with 0.11% Zr and decreased by 9.6% and 7.3% with 0.46% Zr addition, respectively.

3D elemental sensitive imaging using transmission X-ray microscopy

Determination of the heterogeneous distribution of metals in alloy/battery/catalyst and biological materials is critical to fully characterize and/or evaluate the functionality of the materials. Using synchrotron-based transmission x-ray microscopy (TXM), it is now feasible to perform nanoscale-resolution imaging over a wide X-ray energy range covering the absorption edges of many elements; combining elemental sensitive imaging with determination of sample morphology. We present an efficient and reliable methodology to perform 3D elemental sensitive imaging with excellent sample penetration (tens of microns) using hard X-ray TXM. A sample of an Al-Si piston alloy is used to demonstrate the capability of the proposed method.

Assessment of intermetallic compound formation during solidificationof Al–Si piston alloys through thermal analysis technique

Multicomponent Al–Si–Ni–Cu–Mg alloys are widelyused as automotive piston materials. The aim of the present work is to studythe complicated formation of different intermetallic compounds during thesolidification of two types of piston alloys: LM13 alloy with 0·9Ni–0·9Cu–1Mgand 3HA alloy containing 2·6Ni–3Cu–0·2Mg. Solidificationevents were detected by three-thermocouple thermal analysis technique, andmicrostructure evaluations were carried out using optical microscopy, scanningelectron microscopy, energy dispersive X-ray analysis and quantitative imageanalysis. In addition to the (Al)+(Si) eutectic reaction,the results show a complicated precipitation of different post-eutectic phases,the most important of which are Al9FeNi, Al3Ni, Al3CuNiand Mg2Si. Ni rich Al9FeNi and Al3Ni phaseshave the highest formation temperatures among other intermetallics, whichare detected in the range of 553–558°C in 3HA alloy and 546–553°Cin LM13 alloy.

Investigation on the Microstructure and Mechanical Properties of New Al-Si Piston Alloys

Dense precipitation of various intermetallic compounds is a common feature in the microstructure of Al-Si piston alloys. In this investigation, microstructure of LM13 alloy and three high Cu-containing Al-Si piston alloys with different amounts of Ni, Fe, and Mn were studied by means of optical microscopy (OM) and scanning electron microscopy (SEM). Chemical composition of the phases was determined by using energy dispersive X-ray analysis (EDX). The precipitation of the phases was studied through thermal analysis of the solidifying samples. Also, tensile properties and hardness of the samples were measured. The results showed that the various intermetallics such as Al12(FeMn)3Si2, Al3Ni, Al9FeNi, and Al3CuNi precipitated during the solidification. The high Cu-containing alloy with optimum levels of Ni (1.8 wt.%), Fe (0.75 wt.%), and Mn (0.3 wt.%) has the highest tensile strength (250 MPa) and hardness (110 BHN) among the other alloys.

Investigation on the Microstructure and Mechanical Properties of New Al-Si Piston Alloys

Investigation on the Microstructure and Mechanical Properties of New Al-Si Piston Alloys

Characterization of tensile fracture in heavily alloyed Al-Si piston alloy

AbstractThis paper focuses on a typical automotive piston material to characterize its fractographic appearance after tensile rupture. The fracture of this heavily alloyed Al–Si alloy takes place in a brittle manner. The consecutive eutectic zone is found to break by debonding of Si platelets from the Al matrix or by fracturing of Si platelets. The various intermetallic particles break up complicatedly under the stress field of the propagating crack. The fracture tends to pass through or approach to the boundary between the eutectic Al matrix and Si platelets and there is a strong interaction between the propagating crack and the obstructing intermetallic compound. A tensile fracture mechanism in the heavily alloyed Al–Si alloy is elucidated.

Supportive strengthening role of Cr-rich phase on Al–Si multicomponent piston alloy at elevated temperature

The microstructure and elevated-temperature strength of an Al–Si piston alloy with 0.5 wt.% Cr and 0.8 wt.% Fe addition were investigated in this paper. The addition of Cr and Fe leads to the formation of α-Al(Fe,Cr)Si phase, which maintains the crystal structure of α-Al(Fe,Mn,Cr)Si phase but has different stoichiometry and morphology from the phase in previous works. Besides, the morphology of δ-Al 3CuNi phase changes because of solid-solved Cr. These changes result in the formation of closed and semi-closed network eutectic colonies. The Cr-rich phases, acting as effective supportive strengthening phase, integrate organically with Ni-rich phases, acting as main strengthening phases. So α-Al phases are successfully encircled by eutectic intermetallic phases, and the slide of α-Al under stress at elevated temperature can be effectively hindered. Thus the ultimate tensile strength of the examined alloy is increased by 26% after 0.5 wt.% Cr and 0.8 wt.% Fe addition.

Wear Characteristics in Al-SiC Particulate Composites and the Al-Si Piston Alloy

The Al-Si alloy with near eutectic composition has been conventionally used as a piston material for automobile applications. It is required to possess high abrasive wear resistance for enhanced life of the engine. The alloy is known to have fairly good wear resistance due to increased percentage of silicon present in fine form. In the present investigation, Al-SiC particulate composites have been studied for their wear resistance against emery paper (400 grit SiC particles) counterface and a comparison has been made with existing piston alloy i.e. Al-Si alloy. The Al-SiC composites have been prepared using Liquid Metallurgy technique employing 2124 Al alloy as the base material with 10 and 20 % SiC particulates by weight. The abrasive wear study has been conducted on a Pin on Disc machine. The wear rate in terms of weight loss per unit sliding distance as well as the volumetric wear rate have been obtained for the Al-SiC composites. The characteristics of worn surface were investigated using SEM. The composites are found to possess very high wear resistance as compared to Al-Si piston alloy. The results have been discussed and important conclusions are outlined.

Quantitative comparison of three Ni-containing phases to the elevated-temperature properties of Al–Si piston alloys

The different contributions of ɛ-Al 3Ni, δ-Al 3CuNi and γ-Al 7Cu 4Ni phases to the elevated-temperature strength of Al–Si piston alloys were investigated in this paper. Four kinds of Al–Si alloy containing different Ni-containing phases were prepared and their UTS values were obtained. The volume fractions and morphology characteristics of ɛ-Al 3Ni, δ-Al 3CuNi and γ-Al 7Cu 4Ni phases were calculated by the analysis of multicomponent phase diagrams and ImageJ software. The different contributions of ɛ-Al 3Ni, δ-Al 3CuNi and γ-Al 7Cu 4Ni phases to the elevated-temperature properties were analyzed. The δ-Al 3CuNi phase was found to have the most effective volume utilization and possess the most efficient contribution to the elevated-temperature strength among the examined three Ni-containing phases, and the strip-like morphology was proved to be the most favorable morphology in the improvement of elevated-temperature strength.