Alloy Cylinder Research Articles

Microstructure, Phase Composition, Mechanical Properties and Tribological Properties of Plasma Sprayed Al-25Si Wear-Resistant Coatings

Owing to the light weight and high energy, the “All-aluminum engine” can reduce fuel consumption and pollutant emissions, showing a great significance in saving resources and protecting the environment, and becoming a research hotspot. However, the aluminum alloy cylinder liners have difficulty withstanding extremely harsh working conditions, such as strong friction and wear, making the engine extremely easy to damage. In this work, Al-25Si wear-resistant coating was deposited by inner hole supersonic plasma spraying technique to improve the wear resistance of the aluminum alloy cylinder liner. The microstructure, phase composition, mechanical properties and tribological properties were tested by SEM, XRD, tribological machine, etc. The results indicated that the coating exhibited an excellent bonding strength of 44.1 MPa, and the average hardness and average friction coefficient of the coating are 267.09 ± 14.85 HV0.2, and 0.20, respectively. The total wear amount, the wear scar width and the wear scar depth of the coating are 2.77 × 10−3 mm3, 654.3 μm and 8.95 μm, respectively, which showed that the coating can significantly improve the tribological properties of the “All-aluminum engine”. The wear mechanism of the coating was mainly interpreted by furrow cutting, extrusion and spalling in two-body abrasive wear, three-body abrasive wear and a small amount of oxidative wear.

Tag-and-Trace Method of α-Al Crystals Applied to Study Solidification and Casting of Aluminum Alloys

In this study, a new tag-and-trace method of α-Al crystals was developed and used to study the dissolution of a rotating Al-3Si-0.15Ti cylinder immersed into a superheated commercial purity aluminum melt. The developed tag-and-trace method consists of tagging the primary crystals of an alloy with the microsegregation of a peritectic forming solute element, e.g., titanium in aluminum alloys. During solidification, the primary crystals form with a high concentration of the peritectic forming solute, decreasing in the adjacent growth regions of the same crystal. After solidification, the solute microsegregation tag in the interior of the primary crystals can be revealed by color etching. In this work, an Al-3Si-0.15Ti cylinder with all the primary α-Al crystals tagged with titanium was immersed into a superheated titanium-free aluminum alloy. The superheat was varied, and all samples were quenched 10s after immersion of the cylinder. The tagged α-Al crystals from the original cylinder could be distinguished from the non-tagged α-Al crystals formed in the thermally undercooled region surrounding the cylinder and during quenching. Indications of liquid penetration were observed in some α-Al crystals, which indicates that disintegration of α-Al crystals may occur during stirring of the alloy cylinder into a superheated alloy.

The Kilogram

Prior to 2018, the standard for the kilogram was a platinum alloy cylinder created in 1889 and stored in Paris. Over the years, the cylinder lost about 50 micrograms of mass by surface ablation. That original kilogram is not what it once was—albeit only fractionally. In this note, Jeremy Bernstein explains how the kilogram is now defined using fundamental constants.

Microstructure related analysis of tensile and fatigue properties for sand casting aluminum alloy cylinder head

The microstructure and mechanical properties of top plate, force wall and bottom plate in low-pressure sand-casting aluminum alloy cylinder head were evaluated at room temperature. The results of the comparison study showed that with different positions of the cylinder head, the microstructure and mechanical properties were considerably different. For the convenience of analysis and discussion, the quality index (Q) was used to characterize tensile test data, which equals ultimate tensile strength plus 150 log elongation. The top plate has the best tensile performance with Q of 443.5 MPa, while the Q of the force wall (292 MPa) and bottom plate (355.5 MPa) is only 66% and 80% of that on the top plate. The tensile properties of the cylinder head are mainly controlled by dendrite arm spacing (DAS), including primary dendrite arm spacing (PDAS) and second dendrite arm spacing (SDAS). The influence intensity varies with the value of DAS. In general, the tensile properties decreased with the increase of DAS. When the aluminum alloy specimen has small DAS (PDAS ≤ 46.49 µm, SDAS ≤ 33.64 µm), Q increases rapidly with the decrease of DAS. However, when PDAS ≥ 104.33 µm, SDAS ≥ 49.82 µm, the effect intensity of DAS on tensile properties is partially reduced. When the number of cycles is 2.5 × 107, the fatigue stress limits of the top plate (69.2 MPa) and bottom plate (70.0 MPa) are highly comparable, which is mainly due to the similar SDAS and eutectic Si average area. Porosity defects also have a significant impact on fatigue performance. The presence of porosity defects increases the scatter of fatigue properties. In addition, more than 90% of the fractures are caused by porosity defects, which indicates that porosity defects are the main factor causing fatigue cracking of low-pressure sand-casting aluminum alloy cylinder head. Therefore, the casting process should be optimized to avoid porosity defects as much as possible in order to improve fatigue performance.

STRUCTURAL DESIGN OF A ROTATING COMPOSITE CYLINDRICAL SHELL OF HIGH-PERFORMANCE CARDING MACHINE

The cylinder is the heart of a carding machine. The composite structure of the cylinder consists of a composite cylindrical shell fixed at both ends that rotates at a constant speed around its axis. A simplified mechanical model of the filament winding composite forming and ribbing a metal cylinder is given, the differential equation of the boundary value problem of the laminated composite cylindrical shell is established, and the method for solving the static and dynamic characteristics is discussed. The PTC Creo5.0/ANSYS Workbench 2020R1 software program was employed to obtain the results used in the design and calculation models of the cylinder rotor structure system of a high-performance carding machine based on different established structural parameters and material combinations. The deformation and the critical speed of the cylinder rotor system under the combined action of the metallic clothing wrapping tension and centrifugal inertia force were calculated. The analysis and calculation results showed that the working speed of the cylinder rotor structure system was far less than its first critical speed, and the system was operating in a rigid or quasi-rigid rotor state. Under the actions of the wrapping tension of the metallic card wire and centrifugal inertia force, the maximum radial deformation of the cylinder was less than 0.06 mm. Both the aluminum alloy and filament winding cylinders were found to be light weight and highly efficient, which provided an important basis and reference in the structural design, processing and manufacturing, assembly, working gap adjustment, and operation maintenance of the cylinder. These characteristics ensured the high-precision operation and efficient carding of the cylinder system. The research results obtained in this study can be used as a reference in the development of high-efficiency carding machines.

Evaluation of the partitioned mechanical properties and the hall-petch relationship of cast aluminum alloy cylinder head

In view of the non-uniform distribution of mechanical properties of cast aluminum alloy cylinder head, the mechanical properties evaluation and microstructure heterogeneity of cylinder head were studied. The results showed that the head plate position of the cylinder head has the best mechanical properties and microstructure characterization, followed by the floor plate and the thick partition plate. The mechanical properties of the floor plate position attenuate with increasing temperature. From 23°C to 300°C, the tensile strength and yield strength decrease in the same range, but the break elongation changes most obviously. The mechanical properties and microstructure characterization of cylinder head in-situ sampling satisfy the Hall-Petch relationship. If the required ultimate tensile strength is not less than 255MPa, the upper threshold of the grain size, by considering the error limit of the Hall-Petch relationship, is 603.4μm, and the upper threshold of secondary dendrite arm spacing is 69.1μm. Meanwhile, established the relationship between hardness and yield strength, the average error of the nonlinear model is 4.35%. The prediction accuracy of the nonlinear model is sufficient to meet the actual needs of the engineering.

Modified analytical model for water entry of two-dimensional elastic cylinders based on continuum theory

This paper is devoted to the modification of analytical model for the water entry of two-dimensional cylinders. Compared with the conventional analytical model, the modified analytical model includes the effect of specific acoustic impedance. Firstly, based on the continuum theory, the mathematical relationship between the water impact on an elastic cylinder and that on a rigid cylinder is deduced, and the influence of specific acoustic impedance on water entry is introduced. Then, the steel cylinder, aluminum alloy cylinder, magnesium alloy cylinder and polyamide cylinder are taken as examples to compare the modified analytical results, conventional analytical results and SPH-FEM results. Among these four materials, the specific acoustic impedance of steel is large, while those of aluminum alloy, magnesium alloy and polyamide are small. The results show that only the conventional analytical results of the steel cylinder are in good agreement with the SPH-FEM results; in contrast, the modified analytical results of all the cylinders are in good agreement with their SPH-FEM results. Finally, the effect of specific acoustic impedance on water entry is validated by existing experimental data. It indicates that the modified analytical model can be used to solve the water entry problems of elastic cylinders of different materials.

An investigating on explosive expanding fracture of 45 steel cylinders by SPH method

The expanding fracture of ductile alloy cylinder subject to the explosion includes multiple fracture modes, such as tensile, shear, and mixed tensile-shear fracture. The mechanism and the factors influencing the fracture processes are still enigmatic and far from understood. In this paper, the smoothed particle hydrodynamics (SPH) method is used to simulate the explosion experiment of 45 steel cylinders shell with different charges of JOB-9003 and RHT-901. The shear fracture, tension-shear mixed fracture modes and the evolution process of cylindrical shell with different charges are discussed. The simulation results are consistent with the experimental trend. The SPH results show that due to the propagation and reflection of shock wave between the inner and outer surfaces of cylinder during the loading stage of detonation wave, the distribution of equivalent plastic strain on wall-thickness of the cylinder is a convex shape, i.e. the strain in the middle of wall-thickness is larger than that of in the inner and outer walls; when loading by a higher explosive pressure (JOB-9003), the fracture cracks initiate from the middle of wall-thickness, and then develop to the inner and outer walls along the direction of maximum shear in loading stage, showingthe shear fracture mode. However, under the loading caused by charge RHT-901 with relatively low pressure, although the crack still starts from the middle of wall-thickness and propagates along the shear direction, the shear crack could not grow through the section of the wall completely in the loading stage; then the cylinder experiences the stage of free expansion, the stress state of unbroken zone changes into triaxial tensile stress state and the structural instability, similar to “necking” occurs in the unbroken zone. Consequently, the cracks turn from the shear direction to the necking zone along the radial direction, showing the mixed tensile-shear fracture mode. The proportion of tension and shear cracks is related to the occurrence time of structural instability. The results show that the explosion expanding-fracture process of a metal cylinders involves the interaction between shock wave and cylinder structure, and cannot be treated as that of a series of expansion rings.

Microstructure and mechanical properties of plasma transferred wire arc spray coating on aluminum cylinder bores

This study examines the microstructure and mechanical properties of plasma transferred wire arc (PTWA) coating of typical alloyed steel, deposited on diecast aluminum alloy cylinder bores. The coating surface and microstructure were characterized in terms of surface roughness, features (i.e., defects, splats formation mechanisms, distribution of oxides, re-solidified particles, and interfacial metallurgical bonding) using laser scanning confocal microscope, scanning and transmission electron microscope (SEM and TEM). Residual stress through the thickness of the coating was measured using X-ray diffraction (XRD) and hole-drilling method. In post-processed samples, compressive residual stress was measured throughout the coating with a value close to 100 MPa at the interface, resulting from the thermal mismatch between coating and substrate materials. In terms of mechanical properties, coating hardness was estimated at both the micro- and nanoscale and examined the influence of microstructure inhomogeneity on the mechanical performance and failure modes. Three-point bending tests and consequent analysis using the equivalent section method yielded stress-strain properties for both the substrate and coating materials with a maximum coating strength averaging 1480 ± 108 MPa. SEM observation of fracture surfaces showed three modes of failure involving coating delamination and breakage, which is related to the deposition process and the various features within the coating.

High-cycle fatigue failure analysis of cast Al-Si alloy engine cylinder head

Due to the premature fracture of several cast Al-Si alloy cylinder heads at the same position during high-cycle fatigue (HCF) bench test, the HCF failure analysis including finite element simulation, microscopic observation and fatigue tests were conducted to determine the root cause of the failure. The results show that the external load was not the main cause of the fracture. The large defects with complex shapes and low compactness near the surface, and the poor surface finish of the water jacket surface are the main causes for the quick initiation of cracks. Furthermore, the alloy at the failure location exhibits relatively high porosity and secondary dendrite arm spacing, accelerating the crack propagation rate. Compared with the alloy at the non-failure locations, the yield strength, ultimate tensile strength and elongation of the alloy at the failure location are reduced by 9.3%, 25.8% and 65.3%, respectively. The fatigue life of the alloy at the non-failure location is several times the alloy at the failure location, verifying that the local large defects and poor microstructure characteristics are the main causes for the low HCF strength of the cylinder head.

Casting defects and microstructure distribution characteristics of aluminum alloy cylinder head with complex structure

Due to the complex structure of the large cylinder head, it is prone to produce uncontrolled casting defects and uneven microstructure distribution. In order to predict the porosity defects and secondary dendrite arm spacing (SDAS) in the as-cast cylinder head, the low pressure casting process of aluminum alloy cylinder head was simulated. Moreover, to verify the accuracy of the simulation results, microscopic observations were performed, in which the simulation results are reasonably matching with that of experiment results. Both simulation and experiment results demonstrate that porosity defects mainly exist in thick walls as well as thick-thin wall junctions. In addition, the top plate presents the finest microstructure, while the microstructure of the force wall is the coarsest. Additionally, the correlation of casting parameters with porosity defects and microstructure was discussed, suggesting that increasing the cooling rate could partially reduce porosity defects. Furthermore, the finding that decreasing the cooling rate can reduce the SDAS of the casting, resulting in a dense microstructure, was drawn. Besides, it has been concluded that regular shapes and thin walls are advantageous for both reducing porosity defects and obtaining uniform microstructures. This provides an effective approach for predicting the casting defects and microstructure of large complex structural castings through numerical simulation. In addition, a quantitative understanding of the casting parameters, complex structure-microstructure relationship for cast aluminum alloys will allow better determination of process parameters based on microstructure and properties requirements of complex components.

Evolution of the microstructure, texture and mechanical properties of ZK60 alloy during processing by rotating shear extrusion

In this work, we use a kind of punch with a shear structure by combining torsion and backward extrusion (BE) to produce a ZK60 alloy cylinder part by rotating shear extrusion (RSE) at 643 K. This process can introduce a torsional shear component on the basis of backward extrusion by changing the direction of plastic flow and increasing the shear deformation amount to make it easier for the material at the bottom of the punch to flow to the barrel wall. Compared with BE, RSE can obviously refine grains and effectively improve the problems of a small deformation amount and insufficient flow of the material at the bottom of the back extrusion punch. The relevant microstructure evolutions of different parts of formed cylinder parts are investigated, and the results show that the proportions of dynamic recrystallization (DRX) in the inner and the middle wall of the lower half region of RSE processed part increase obviously (by 49% and 21.7%, respectively) and that the size of fine grain is ~2–4 µm; further, that of the bottom of the barrel increases by 44.6%. The deformation mechanisms of rotating shear are mainly continuous DRX (CDRX) accompanied by discontinuous DRX (DDRX) in the early stage, and with the progress of deformation, DDRX plays a leading role. The (0001) plane in the BE processed part is basically parallel to the transverse direction (TD), while the (0001) plane in the RSE part is deflected to the extrusion direction (ED) and at an angle of 30°−45° to the TD, and the texture strength is obviously weakened. A comparison of the variation in ∆Hv(%) along the TD of the barrel wall of the two extruded parts shows that RSE can generate a larger deformation amount and wider deformation effect range under the same extrusion ratio, effectively improving the microhardness of the ZK60 alloy. The ultimate strength (UTS), yield strength (YS), and elongation (EL) of alloy are ~313 MPa, ~279 MPa, ~12.1% after the RSE process, respectively. And the strength and ductility of the alloy can be improved by the RSE process.

Microstructure and mechanical properties of the sub-rapidly solidified Mg―Zn―Y―Nd alloy prepared by step-copper mold casting

In this paper, the microstructure and compression mechanical properties of the sub-rapidly solidified Mg‒Zn‒Y‒Nd alloy cylinders with diameters of 2–8 mm prepared by step-copper mold casting were investigated. The cooling rate of samples increased gradually with decreasing the mold diameter. The ϕ2-mm sample consists of α-Mg with the smallest grain size of about 10 μm and spherical T-phase, rod-like I-phase, ribbon-like Mg7Zn3 phase, skeleton-like W'-phase. With a decrease in the cooling rate, the grain size of α-Mg increases and the secondary phases are coarsened. For the ϕ6-mm and ϕ8-mm samples, I-phase and W'-phase disappear, W-phase appears and tends to form network structures. Among these samples, the ϕ2-mm one exhibits the highest ultimate fracture strength of 384 MPa and the largest plasticity of 30 %. The good mechanical properties were attributed to the activation of non-basal <c + a> slips at the later stage of deformation. This result suggests that the sub-rapid solidification technique would be a promising way to improve the mechanical properties of Mg alloys, which can be used as biodegradable mini-implants.

Study on Coating Material and Preparation Technology of Aluminum Alloy Tube by Low Temperature Self-Propagating Molding

Low temperature self-propagating forming coating material system for aluminum alloy cylinder parts was designed with Al, Fe2O3, Mo, Cu, Ni and Ti powders as raw materials. Low temperature self-propagating wear-resistant coating was prepared on the inner wall of aluminum alloy cylinder parts by thermal spraying ignition condensation centrifugal self-propagating fusion technology. XRD, DSC and SEM were used to study the microstructure, thermodynamic properties and cross-section morphology of the coating after thermal reaction of four kinds of low-temperature self-propagating materials with different proportions. The preparation process parameters of the coating were optimized by orthogonal test, including the amount of coating, the rotation speed of self-propagating centrifuge and the reaction time of self-propagating coating. The results show that the addition of Si, Mo and Zn powders in the four low temperature self-propagating powder systems can reduce the occurrence temperature of aluminothermic reaction; the optimal process parameters for coating preparation are rotational speed of 2000r/min, powder filling amount of 0.9g/cm3 and rotational reaction time of 16S.The results show that the coating with 20wt.% Al, 60wt.% Fe2O3, 12wt.% Si, 4wt.% Mo and 4wt.% Zn has better density and interface adhesion.

An alternative ex vivo method to evaluate the osseointegration of Ti–6Al–4V alloy also combined with collagen

Due to the increasing number of orthopedic implantation surgery and advancements in biomaterial manufacturing, chemistry and topography, there is an increasing need of reliable and rapid methods for the preclinical investigation of osseointegration and bone ingrowth. Implant surface composition and topography increase osteogenicity, osteoinductivity, osteoconductivity and osseointegration of a prosthesis. Among the biomaterials used to manufacture an orthopedic prosthesis, titanium alloy (Ti–6Al–4V) is the most used. Type I collagen (COLL I) induces cell function, adhesion, differentiation and bone extracellular matrix component secretion and it is reported to improve osseointegration if immobilized on the alloy surface. The aim of the present study was to evaluate the feasibility of an alternative ex vivo model, developed by culturing rabbit cortical bone segments with Ti–6Al–4V alloy cylinders (Ti-POR), fabricated through the process of electron beam melting (EBM), to evaluate osseointegration. In addition, a comparison was made with Ti-POR coated with COLL I (Ti-POR-COLL) to evaluate osseointegration in terms of bone-to-implant contact (BIC) and new bone formation (nBAr/TAr) at 30, 60 and 90 d of culture. After 30 and 60 d of culture, BIC and nBAr/TAr resulted significantly higher in Ti-POR-COLL implants than in Ti-POR. No differences have been found at 90 d of culture. With the developed model it was possible to distinguish the biomaterial properties and behavior. This study defined and confirmed for the first time the validity of the alternative ex vivo method to evaluate osseointegration and that COLL I improves osseointegration and bone growth of Ti–6Al–4V fabricated through EBM.

Evaluation and Analysis of RT Suspected Defects on Reactor Pressure Boundary Weld

The control rod driving mechanism (CRDM) is one of the important equipments in the nuclear reactor, and its sealing shell is part of the pressure boundary of the nuclear reactor. The sealing shell is a pressure vessel made of two different material (austenitic stainless steel and nickel base alloy) cylinders welded by dissimilar metal welds. Product production process, in this dissimilar metal weld ray detection found suspected defects show. In this paper, the mechanism and process of the suspected defects are expounded through experimental verification, and it is proved that the suspected defects do not affect the quality of the weld.

RoHS 규제에 따른 동합금 실린더블록 내마모성 분석

RoHS 규제에 따른 동합금 실린더블록 내마모성 분석

An experimental investigation on fretting wear behavior of copper–magnesium alloy

The fretting wear behavior of copper–magnesium alloy (Cu–Mg alloy) used for high-speed railway catenary system was investigated. Fretting tests of Cu–Mg alloy cylinder against Cu–Mg alloy cylinder at vertical cross contact configuration were carried out on a fretting wear rig at room temperature. The running condition fretting map (RCFM) composed of partial slip regime (PSR), gross slip regime (GSR), and mixed fretting regime (MFR) was constructed depending on different normal loads and displacement amplitudes. In PSR, only slight surface damage was detected on the wear scar. In MFR, the morphologies of the wear scar displayed a clear subdivision in the central stick zone and the surrounding annular slip zone. Fatigue cracks initiated and propagated at the boundary between the stick zone and slip zone. The damage mechanism is the combination of fretting fatigue and fretting wear which combines adhesion, surface fatigue and slight tribochemical reactions. In GSR, fretting wear is predominant. The wear mechanisms were mainly abrasion, surface fatigue and severe tribochemical reactions dominated by oxidation.

Microstructure and texture of Ti-6Al-4V alloy deformed by rotary forging at elevated temperatures

Abstract Ti-6Al-4V alloy cylinder samples were subjected to rotary forging at temperatures ranging from room temperature to 1 473 K. The microstructure and texture were examined by means of electron back-scatter diffraction and X-ray diffraction. The results indicated that the rotary forging could remarkably promote formability at elevated temperatures but not room temperature. For the 1 073 K and 1173 K samples, dynamic recrystallization led to a notable grain refinement effect and produced a typical basal texture. With the further increase of deforming temperature to 1 473 K, dislocation slip contributed the main deformation and the effect of grain refinement was weakened. The martensitic transformation took place during the cooling process of the 1 473 K sample, forming a strip type microstructure and a special texture different from basal texture.

Microstructure and texture of Ti-6Al-4V alloy deformed by rotary forging at elevated temperatures

Abstract Ti-6Al-4V alloy cylinder samples were subjected to rotary forging at temperatures ranging from room temperature to 1 473 K. The microstructure and texture were examined by means of electron back-scatter diffraction and X-ray diffraction. The results indicated that the rotary forging could remarkably promote formability at elevated temperatures but not room temperature. For the 1 073 K and 1173 K samples, dynamic recrystallization led to a notable grain refinement effect and produced a typical basal texture. With the further increase of deforming temperature to 1 473 K, dislocation slip contributed the main deformation and the effect of grain refinement was weakened. The martensitic transformation took place during the cooling process of the 1 473 K sample, forming a strip type microstructure and a special texture different from basal texture.