As-cast Specimens Research Articles

Third-generation biodegradable bone implants: A novel Mg-1Zn-0.5Sc alloy treated by laser shock peening to improve its characteristics

Magnesium (Mg) and its alloys are of much interest as promising third-generation bio-materials for bone implant applications; however, challenges remain for the alloy's mechanical integrity and bio-corrosion behaviour. Therefore, appropriate alloying elements and surface-modification techniques are required to overcome these limitations. Zinc and scandium were found to possess good biocompatibility and biodegradability, in addition to magnesium. This study aims to enhance the mechanical integrity and bio-corrosion resistance behaviour of a novel Mg-1wt% Zn-0.5wt% Sc cast alloy by laser shock peening surface treatment with multiple passes (LSP-2 pass and LSP-3 pass). The microstructural and texture evolution was investigated using various techniques, including field emission scanning electron microscopy with energy-dispersive spectroscopy (FESEM-EDS), optical microscopy (OM), X-ray diffraction (XRD) analysis, electron back-scattered diffraction analysis (EBSD), as well as the surface residual stress, wettability, microhardness, tensile strength, electrochemical polarization test, and biocompatibility were analysed on as-cast, LSP-2 pass and LSP-3 pass specimens. LSP induced beneficial compressive residual stress around the surface and sub-surface region of Mg-1Zn-0.5Sc alloy due to severe plastic deformation, which led to grain refinement through the twinning mechanism of the Mg alloy. Also, the dispersion of second-phase particles (β-ScZn) was observed while analysing the XRD profiles. Strain hardening, grain refinement, and precipitate strengthening have contributed to the structure and texture evolution, which enhanced the microhardness, tensile strength, ductility, and corrosion resistance of the Mg-1Zn-0.5Sc alloy. From in vitro studies, a low rate of corrosion in simulated body fluid and less cytotoxic behaviour were observed for the LSP-3 pass Mg-1Zn-0.5Sc alloy.

Strengthening phase and mechanical property analysis of artificially aged Al7075 – Ni coated Al2024 composites

This technical paper demonstrates the possibilities of nickel (Ni) coated Al2024 powder reinforcement in an Al7075 matrix using the liquid stir casting technique. Additionally, the paper focuses on achieving stable properties by implementing artificial aging heat treatment. To apply the Ni coating, the electroless nickel plating technique was utilized, and a minimum coating thickness of 8 μm was determined to effectively prevent the dissolution of Al2024 powder reinforcements within the Al7075 matrix. Stir casting facilitated the uniform dispersion of the coated Al2024 powder up to a weight percentage of 7%. Subsequently, the Al7075 alloy and composites underwent artificial aging through solution heat treatment (SHT) at 450 °C for 4 h, followed by water quenching and aging at temperatures of 120, 150, and 180 °C. Aging at 120 °C was found to yield superior results compared to aging at 150 and 180 °C, thus identified as the optimum aging temperature. When the Ni coating thickness was increased beyond the optimal 8 μm, the resulting enhancements in hardness for both as-cast and peak-aged specimens, as well as the tensile strength, were not significant. The improvements observed were only marginal, ranging between 2 to 3%. Fracture surface analysis revealed that the predominant fracture mode in the Al7075 alloy was ductile, characterized by dimple rupture. In the as-cast Al7075-(7%, 8 μm) Al2024 composite, a mixed fracture mode comprising both brittle and ductile characteristics was observed. In the peak-aged (120 °C) Al7075-(7%, 8 μm)Al2024 composite, the overall fracture mode exhibited a dominant brittle nature. Analytical techniques including XRD, TEM, and EDS confirmed the presence of Mg2Si, MgZn2, CuAl2, and CuAl2Mg phases in the peak-aged (120 °C) Al7075-(7%, 8 μm) Al2024 composite. These phases contributed to the enhancement of the properties of both the Al7075 alloy and its composites. The developed composites can be used in automobile parts and aerospace applications.

Comparison of Solidification Microstructure Evolution of Al-10Si and Recycled Aluminium Beverage Can Strips Made in a Strip Caster

A strip caster was used to cast two types of aluminium alloys: an almost eutectic Al-Si alloy (Al 10 Si) with contaminants of 0.6 Fe, 0.2 Pb, and 1.4 Sn, which exhibits a polyphase microstructure upon solidification, and recycled aluminium beverage cans made from Al 0.8 Mn alloy containing 0.4 Si, 0.5 Fe, and 0.1 Mg, which has a monophase microstructure upon solidification. The molten materials were poured at 650 oC (Al 10 Si) and 670 oC (Al 0.8 Mn, 0.4 Si, 0.5 Fe, 0.1 Mg) on a cooling slope specially designed to obtain a semisolid material. This semisolid material was then dragged between rolls at a rate of 0.2 m/s to obtain high-quality metal strips. There was less eutectic modification with larger Al-α grains in the middle region of the sheet between the fine eutectic layers, indicating a lower cooling rate. However, during the recycling of aluminium beverage cans, large grains were formed with a columnar structure at the interface of the rolls, and semisolid melts with cracks were formed between the columnar grain boundaries owing to the compression of the rolls. The middle of these grains contained smaller equiaxial grains that were subjected to dragging. The as-cast specimens were submitted to homogenisation heat treatment at 560 oC for a period of 10 h and cooled to room temperature before being cold rolled (Temper H18) and recrystallised (Temper O) to examine the effect of these treatments on the tensile mechanical properties. During cold rolling (Temper H-18), grain alignment occurred with a yield stress, maximum stress, and elongation of 209.5 MPa, 210.1 MPa, and 2.8%, respectively. The strength decreased (yield stress of 58 MPa and maximum stress of 120.2 MPa) under recrystallisation conditions (Temper O), but the ductility increased (8.9%). This is in contrast to the Al-Si (Al 10Si) strip, which exhibited a yield stress, maximum stress, and elongation of 103.3 MPa, 128.7 MPa, and 1.9%, respectively. The A1 10Si strips also fractured during cold rolling, indicating high material fragility.

Investigation of the mechanical, corrosion, and tribological characteristics of AZ61 Mg with boron carbide nano particles via the stir casting route

Abstract Magnesium composites are innovative, compact, and distinctive materials. Because of their low density, magnesium composites are suitable for applications in the automobile, aviation, semiconductor, and pharmaceutical sectors. To enhance the mechanical wear and corrosion behavior of theAZ61 Mg alloy, different weight percentages of nano-B4C reinforcements (2.5, 5, 7.5, and 10wt%) were strengthened with magnesium matrix. Fabrication of magnesium composites was achieved through the stir casting method. The as-cast specimens were subjected to microstructural analysis, which showed that the B4C nanoparticles were dispersed uniformly, well bonded to the matrix, and had a minimal level of porosity. This shows that the inclusion of B4C nanoparticles has aninsignificanteffect on the microstructure of the as-cast material. The material’s tensile strength, compressive strength, hardness, corrosion resistance, and wear resistance were all greatly increased by the Mg17Al12 phase’s fracture and dispersion. Scanning electron microscopy was utilized to inspect the surfaces of AZ61/B4C nanocomposites and witnessed the uniform dispersal of reinforcement within the matrix.The maximum value for mechanical properties was obtained for AZ61/7.5wt%B4C nanocomposite and the lowest value was found to be the corrosion test. These results show that the AZ61/7.5wt%B4C nanocomposite is a superior material for aerospace and automotive engineering components where high compressive strength, corrosion resistance, and wear resistance are required.

Microstructural homogeneity, texture and corrosion properties of RE-doped 55Mg-35Pb-9.2Al-0.8B alloy fabricated via equal channel angular pressing (ECAP)

A fine-grained 55Mg-35Pb-9.2Al-0.8B alloy was fabricated through equal channel angular pressing (ECAP) with the addition of rare earth (RE). The corrosion behavior of the alloy was investigated by electrochemical test, hydrogen evolution test and salt spray test. The results demonstrate the corrosion resistance ranking of the as-cast specimens with RE elements as follows: 0.5Sc > 0.5Y > 0.5Sm > 0.5Ce > 0.5Nd > as-cast. After the 1st ECAP process, the corrosion resistance of the alloy samples follows this order: 0.5Sc > 0.5Ce > 0.5Y > 0.5Sm > 0.5Nd > as-cast. The addition of 0.5Sc has the most significant effect on the improvement of corrosion resistance of the alloy. At the same time, the corrosion resistance of 0.5Ce alloy was improved after ECAP. The microstructure of 55Mg-35Pb-9.2Al-0.8B alloy was refined and the dispersion of the second phase was reduced by adding RE elements and ECAP. Grain refinement can stabilize the corrosion product layer and improve corrosion resistance. This study lays the foundation for comprehending and future applications of the ECAP process in fabricating high-performance Mg-Pb-Al-B-RE alloys.

Phase equilibria and thermodynamic re-assessment of the Cu–Ti system

Several as-cast and annealed Cu–Ti alloys were prepared for microstructural, compositional, structural and thermal characterizations. The formation of CuTi2 was congruent and CuTi3 was not found in both as-cast and annealed specimens. The temperatures of nine invariant reactions were determined. The Cu–Ti system was thermodynamically re-assessed according to the experimental phase equilibria and thermochemical properties from this work and the literature. The solution phases Liquid (L), fcc-A1 (Cu), bcc-A2 (βTi) and hcp-A3 (αTi) were treated as substitutional ones. The intermetallics compounds Cu2Ti, Cu3Ti2, Cu4Ti3 and CuTi2 with negligible solubility were described as line ones with the formula CupTiq, while βCu4Ti and CuTi with remarkable solubility were modeled with the formula (Cu,Ti)r(Cu,Ti)s. A group of reliable thermodynamic parameters of the Cu–Ti system were obtained. The calculated results agreed reasonably well with the experimental ones.

Modeling of extremely ductile behavior of Zr-based bulk metallic glasses under compressive strain paths for solid-state processing

In addition to extremely high strength, manufacturing temperatures of bulk metallic glasses (BMGs) relative to steels are low making them to desired energy saving engineering materials. However, BMGs are significantly brittle at low temperatures. To further increase suitability of BMGs for widespread use, it is essential to understand their plastic deformability (ductility) for high-tech solid-state processes at lowered temperatures. In this work, extremely large deformation behavior (near 80% in compression) of industrially important Zr-based BMGs was investigated. The experimentally measured results aided in the development of an appropriate constitutive model and revealed the micromechanisms affecting the characteristic macroscopic deformation behavior including softening and hardening. The measured and model results showed that the ductility can be significantly improved through chemical composition changes, such as a reduction in the Cu content and an increase in the Zr, Ti, or Be contents. In contrast to previously announced conclusions on the high glass-forming ability (GFA) being the precursors to ductility, formation of sufficiently low degree of crystallization during cooling improved ductility of as-cast specimens under loadings. These observed properties are important in assessing the ability of BMGs for solid-state processing.

Structure and properties of CoCrFeNiMnBe high-entropy alloy films obtained by melt quenching

In this study nanostructured films of the Co16.67Cr16.67Fe16.67Mn16.67Ni16.67Be16.67 high-entropy alloy have been synthesized by the method of melt quenching. The structure and physical properties of melt quenched films and as-cast specimens of identical composition were investigated. The XRD patterns allowed us to establish that the investigated alloy in the as-cast state has a multiphase structure in which there are the FCC phase with lattice parameter a = 0.3598 nm, BCC phase (a = 0.2872 nm), and B2-type intermetallic compounds BeNi(Co) (a = 0.2616 nm). At the same time, the melt quenched sample has a structure consisting of the FCC phase (a = 0.3579 nm), the BeNi(Co) phase (a = 0.2610 nm) and the minor BCC phase. Both as-cast specimens and melt quenched films reveal a typical ferromagnetic behavior and exhibit semi-hard magnetic properties and high mechanical characteristics.

Optimisation of melt pouring temperature and low superheat casting of Al-15Mg2Si-4.5Si composite

ABSTRACT In this study, a computational fluid dynamics (CFD) model is employed to optimise the melt pouring temperature during Low superheat casting (LSC) of the Al-15 Mg2Si-4.5Si composite. The die cavity considered to perform the die filling simulations corresponds to the as-cast tensile specimens, as per ASTM B557 guidelines. The findings of the study include melt temperature distribution, solid fraction distribution during filling as well as during solidification, velocity distribution of the melt and surface defect concentration. Experimentation is performed to develop low superheat cast composite based on the numerically estimated optimum melt pouring temperature of 650°C. Mixture of irregular dendritic, polygonal and equiaxed shaped primary Mg2Si grains are observed within the cast parts, whereas primary Al grains are found to be of dendritic morphology with occasional presence of spheroids. Marked improvements in microstructure and mechanical properties have been evidenced in the LSC composite compared to its conventional cast counterpart.

The influence of heat rate and austenitization temperature on microstructure and hardness of Hadfield steel

The As-Cast condition of Hadfield alloy usually contains (Fe, Mn)3C carbides around the austenitic grains, which promote brittleness, making the steel impractical in industry. Heat treatment is normally applied to reduce carbide content, lower carbides, and improve toughness. However, a complete austenitic structure is not attainable during solution treatment. The dissolution temperature and dissolution time are critical to obtaining complete carbide content. Furthermore, heating must be done slowly, and the quenching speed must be fast enough. This study examines the effect of heat rate and austenitization temperatures in the solution treatment on the microstructure and hardness of Hadfield steel. The heat rate of 3, 6 and 10 oC/min is selected to determine whether there is a change in the microstructure of Hadfield steel. The four austenitization temperatures of 1000, 1100, 1150 and 1200 oC are used to ascertain carbide dissolution into the austenite matrix. Grain boundary, hardness, and phase transformation will confirm the microstructural change and hardness properties. The optical microscope shows carbide content is reduced as the austenitization temperature increases. The consequence of carbide dissolution affects the hardness. Its hardness decreases as temperature increase due to the loss of carbide. The as-Cast specimen has the highest hardness of 227.8 HV30, and the lowest hardness is 176.7 HV30 belongs to a specimen that is heated up to 1200 °C and quenched into water. Grain size is measured by the line intercept method, which shows its increase as temperatures increase. The result of grain measurement is as follows: As-Cast 224.6 mm, T 1000 °C 323.3 mm, T1100 °C 409.2 mm, T1150 °C 1014.4 mm, T1200 °C 881.6 mm. SEM-EDS confirms that the main phase is austenite, and a small amount of carbide is detected in the austenite matrix.

Tribological properties of novel Al 7075(T6)-SiC-crumb rubber-MoS2-based hybrid composites: An experimental approach towards green revolution

In the present study, an experimental approach is conducted for analyzing the tribological attributes of the novel green hybrid metal matrix composites fabricated by an advanced vacuum-sealed bottom pouring stir casting comprised of Al 7075(T6) as a base metal doped with three distinct reinforcements as silicon carbide, crumb rubber, and molybdenum disulfide. Six casting process variables such as SiC, crumb rubber, MoS2, stirring speed, stirring time, and pouring temperature have opted for the fabrication of green hybrid composites via Taguchi L18 mixed-level orthogonal array. Tribological studies (in terms of wear loss, frictional force, and coefficient of friction) on fabricated green composites are examined via the high-temperature rotary pin-on-disc tribometer with fixed process parameters (such as wear track diameter, sliding speed, normal load, sliding distance, disc rotation speed, and test duration) under dry sliding wear test. Moreover, the wear test is also executed under variable temperature conditions of 35 °C, 100 °C, 200 °C, and 300 °C. The metallography of synthesized green composites and their worn surfaces is inspected via a metallurgical microscope and scanning electron microscopy–energy dispersive X-ray spectroscopy techniques. Besides, the analysis of variance is implemented to predict the percentage contribution of the combined process variables for wear loss analysis. In contrast to the as-cast specimen (S0), the developed hybrid pin specimen (S3) yields a tremendous improvement in its metallurgical and tribological attributes under varying temperature conditions. Owing to the merits of the proposed composite, it can be extensively used in lightweight, high-temperature, and wear-resistant applications of various automotive and aerospace engineering.

Enhancement in dispersoid precipitation and dispersion strengthening by prior deformation in an Al–Mg–Mn alloy

Dispersion strengthening effect of Mn-containing dispersoids in the non-age hardenable Al–Mg–Mn alloys is generally limited since it is difficult to achieve the high-density and fine sized dispersoids through conventional homogenization treatment. In this work, inspired by the heterogeneous precipitation along dislocation for Mn-containing dispersoids, strain induced dislocations was introduced by prior deformation to increase the nucleation sites in the matrix. Based on the classical nucleation theory, the nucleation rate in the pre-strained specimen is improved by an order of magnitude compared with that of the as-cast specimen. Detailed electrical conductivity tests and transmission electron microscopy observations showed that prior deformation can promote the decomposition of supersaturated solid solution and successfully increase the number density of Mn-containing dispersoids, but decrease their sizes from 323 ± 83 nm to 118 ± 43 nm in long axis dimension after homogenization treatment. An improvement of 36.5 MPa in yield strength can be achieved through the enhanced dispersion strengthening mechanism. Simultaneously, the diffusion distance of Mn solute atoms dramatically increases from 0.85 μm to 27 μm due to the enhancement in diffusivity, which can be mostly attributed to the increase in diffusion paths caused by the higher density of strain-induced dislocations. Thus, the volume fraction of dispersoid free zones was decreased by 51% in the pre-strained specimen, indicating that a more uniform distribution of dispersoids in the Al matrix can be obtained by prior deformation. This work provides some insight into the enhanced dispersion strengthening effect of Mn-containing dispersoids by prior deformation, which is a promising approach to further improve mechanical properties of non-age hardenable Al alloy.

The Influence of Annealing at 500 and 900 °C on the Structure and Mechanical Properties of AlxCoCrFeNi Alloys.

The AlCoCrFeNi high-entropy alloy is sensitive to heat treatment. The aim of the present study was to test a similar correlation for AlxCoCrFeNi alloys with less than equimolar aluminum content. This paper presents a study of the annealing effect on the structure and mechanical properties of selected alloys. AlxCoCrFeNi alloys (x = 0, 0.5, 0.7) were fabricated by the induction melting method. The obtained specimens were annealed at 500 °C and 900 °C. A detailed study of the changes in crystalline structure due to annealing was conducted. Three-point bending and hardness tests were carried out for the as-cast and annealed specimens to determine selected mechanical properties. The study confirmed that increasing the aluminum content in the AlxCoCrFeNi alloy improves mechanical properties. For the alloy with aluminum content x = 0.7, hardness increased by 187% and yield strength by 252% compared to the alloy without aluminum. A significant effect of annealing on the crystalline structure of the Al0.7CoCrFeNi alloy was found, but this was not followed by changes in mechanical properties.

Development of a high strength, low density and corrosion resistant novel FeCrMoNb1.5Ti0.5 complex concentrated alloy

The present work deals with the microstructure, mechanical properties and corrosion behavior of a FeCrMoNb1.5Ti0.5 complex concentrated alloy (CCA). The aforementioned alloy was fabricated by vacuum arc melting technique. The observed density and lattice parameters of the as-cast alloy are 7.821 g/cm3 and 3.179 ± 0.003 Å, respectively, which follow the rule of mixture. The phase evolution, chemical composition, and microstructure in the as-cast condition, as well as after annealing treatment at 800°C, 1000°C, and 1200°C, were investigated through XRD, TEM, and SEM-EDS. The XRD and TEM analyses confirmed the presence of BCC structure with minor amount of TiCr2 type and NbCr2 type C14 Laves phases. Instrumented micro-indentation and corrosion testing were performed in the as-cast and annealed specimens. The microhardness of the as-cast alloy was 825 HV and it increased to 1102 HV after annealing at 1200ºC for 20 h. This peak hardness was achieved after annealing at 1200ºC due to the presence of a large volume fraction of Laves phase. Potentiodynamic polarization tests of the as-cast and as-annealed specimens revealed outstanding corrosion resistance of the CCA compared to stainless steel. This is attributed to better microstructural homogeneity and reduced elemental segregation after annealing.

Ultra-fine Nbss/Nb5Si3 in situ composites with remarkable properties prepared by ultrasonic melt treatment

In order to refine coarse silicide and improve mechanical performance of ternary Nb-20Si-5Mo alloy, ultrasonic vibration treatment for ultra-high temperature melt is successfully applied. The results show that the vibration can improve the fluidity and reduce the shrinkage defects. The hypereutectic microstructure transforms into the fine rod-like eutectic. Due to the solute redistribution in ultrasound field, the Mo-rich layer at Nbss and β-Nb5Si3 phase boundary and the semi-coherent relation can be observed. Mo tends to dissolve in Nbss the matrix phase and inhibit the peritectic reaction. The average size of primary silicide is refined from 49.1 to 2.2 µm with 95.52% refinement efficiency, the compressive strength and fracture toughness of 100 s ultrasonic treated specimen improved 6.84% and 50.75% compared with the as-cast specimen, respectively. The heightened constitutional supercooling and the accelerated nucleation caused by cavitation effect are the main reasons of grain refinement.

Effect of Cu Addition on Solidification Microstructure in High Carbon High Speed Steel Type Cast Alloy

Effect of copper addition on solidification microstructure was investigated for high carbon high speed steel type alloys (Fe-2.0%C-5%Cr-5%Mo-5%V-0~4%Cu). The microstructure of all as-cast specimens with different copper content was composed of dendrite of primary γ, MC-γ eutectic and M2C-γ eutectic but it was found X-ray diffraction peaks of α phase by X-ray diffractometry. The volume fraction of each phase in solidification microstructure was approximately constant regardless of copper content. The shapes of dendrite of primary γ changed significantly in response to amount of copper addition: that of specimen with no copper was equiaxed while that of specimen containing copper was columnar which tends to be marked with increasing amount of copper addition. Furthermore, the secondary dendrite arm spacing λ2 decreased with increasing amount of copper addition. As a result, it concluded that the effect of copper addition on solidification microstructure is columnar crystallization and decreasing λ2 of the dendrite with primary γ.

Microstructure characteristics of a René N5 Ni-based single-crystal superalloy prepared by laser-directed energy deposition

This work focused on the microstructure and mechanical properties of nickel-based single crystal (SX) superalloy René N5 prepared by laser-directed energy deposition (L-DED) using a flat-top laser beam. A comparison was conducted with the conventional directional solidification technique. Results show that the crack-free single-crystal superalloys with a fraction of low-angle grain boundary (LAGB) higher than 98.5% were obtained by epitaxial growth under different laser powers. The flat fusion line using a flat-top laser beam can suppress the formation of stray grain and high-angle grain boundaries (LAGB) during the L-DED process. Microstructure observation shows the extremely refined dendrites in L-DED SX superalloys with primary dendrite arm spacing (PDAS) values around 20–30 µm, which is significantly lower than as-cast ones (∼350 µm). PDAS increases with the increasing laser power. Segregation of refractory elements of Re, W, and Ta increases with increasing laser power, and the SX specimens with laser power of 1100 W and 1300 W have lower elemental segregation compared with as-cast specimens. The SX specimens exhibit a uniform square γ′ phase at the dendrite core, with an average size of 79–101 nm and a volume fraction of 57–68%. Besides, the carbides with discontinuous and refined shapes show a uniform distribution in the L-DED specimens in comparison with as-cast specimens. The microhardness of as-deposited specimens increases with the increasing laser power, which is higher than that of as-cast ones. This work can provide potential guidance for the microstructure control in the laser additive manufacturing of Ni-based SX superalloys and a further improvement in high-temperature mechanical performance.

Effects of solidification rate and heat treatment on microstructure characterization and hot tensile strength of single crystal CMSX-4 superalloy

Single crystal CMSX-4 Ni-based superalloy, consisting of rhenium and hafnium elements, were directionally solidified at three different withdrawal rates of 2, 3, and 4 mm/min through a Bridgman furnace. After that a full solution heat treatment was followed by two step aging at 1140 °C/6 h and 870 °C/20 h respectively. Microstructural characteristics, e.g. the primary and secondary dendrite arm spacing, the size and volume fraction of γ ́ phase, and percentage of porosity were analyzed using the optical microscopy (OM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS) detector. It was found that an increase in the withdrawal rate of the as-cast specimens led to a reduction in the values of primary and secondary dendrite arm spacing, the percentage of porosity and also size of γ ́. In addition, at higher withdrawal rates, the γ/γ ́ eutectic phase is distributed from a continuous and blocky shaped to fine scattered islands. Nevertheless, the minimum volume fraction of eutectic was obtained at the withdrawal rate of 3 mm/min. Heat-treatment of the specimens associated with formation of a noticeable cuboidal γ’-precipitates, which was about 70% at withdrawal rate of 3 mm/min. Furthermore, the aged specimens indicated the lower γ/γ ́ eutectic phase compared to as-cast specimens, while the percentage of porosity increased for aged specimens. Eventually, the highest ultimate tensile strength of the single crystal CMSX-4 at 870 °C was measured to be 1170 MPa which was obtained at a withdrawal rate of 3 mm/min, due to the high volume fraction of the γ ́ phase and the lower values of γ/γ ́ eutectic phase.

EXPERIMENTAL INVESTIGATION ON ENERGY CONSUMPTION AND SURFACE FINISH IN TURNING OF Al-4032/6% SiC COMPOSITE FABRICATED THROUGH STIR CASTING

The aluminum-based composites (AMCs) are known for a variety of functions like building, aerospace, automotive, marine, and aeronautical applications. In this research, Al-4032 alloy-based 6% SiC (by weight) composite has been fabricated using stir casting and the effects of prominent machining parameters on energy consumption and surface finish have been examined using carbide inserts in turning. Microstructures of as-cast specimens has been analyzed using the optical microscope, scanning electron microscopy, and energy-dispersive spectroscopy. The CNC turning has been performed at varying machining parameters like cutting speed, feed rate, and depth of cut, following an RSM-based design matrix. The desirability function approach has been employed to obtain the best combination of parameters for achieving the desired objectives. The experimental outcome demonstrates that the machined composite is considerably influenced by built-up edge (BUE) formation and interfacial bonding of particles. The result establishes that the inclusion of SiC in the Al-4032 matrix demonstrates improved mechanical properties and superior machined surface with the optimized turning operation.

Influence of ageing on fatigue properties of graphite reinforced aluminium composites

ABSTRACT Impact of age hardening and incorporation of graphite particles reinforcements on fatigue properties of Aluminum metal matrix composites which were fabricated with liquid metallurgical method is explored in this paper. Fabricated fatigue testing specimens were age hardened at temp of 170 °C and 270 °C to improve fatigue strength. Both aged and ascast specimens were characterized to study fatigue properties at operating temperature.Ggraphite particulate and age hardening temperature influences the fatigue strength of composites owing to its higher fatigue life compaed with as cast condition and age hardening at 270 °C. The incorporation of graphite exhibited remarkable improvement in fatigue strength. The detailed study of fractured surfaces of composites under microscope revealed its failure mechanism. It is found that , hardness increased with aging temperature up to 170 °C, beyond which found to be decreased resulted in formation of precipitation near the grain boundaries and enhanced the hardness of composites. But at 270 °C, both precipitate and grain boundaries abrading reduces both strength and hardness of composite. EDS analysis of composites at different phases for particles and interface between matrix and graphite particles is shown rich phase in aluminium matrix and poor at the interface.