Revista de Metalurgia

Machinability of B4C-reinforced Al2014 metal matrix composites in electric discharge machining

2022-12-27T10:31:36+01:00

This study was conducted to clarify the effect of various variables such as the type of electric discharge machining, discharge current and reinforcement content of B₄C-reinforced Al alloy metal matrix composite on workpiece removal rate, electrode wear rate and material removed per discharge pulse, which are not extensively explored in the literature. B₄C-reinforced Al2014 matrix composite samples containing 5 and 10 vol.-% B₄C particles, produced by vacuum infiltration method, were machined with electric discharge machining and powder mixed electric discharge machining at various discharge current settings. In both types of machining processes, the workpiece removal rate and electrode wear rates decreased and increased, respectively, when the reinforcement contents of the composites increased. However, powder-mixed electric discharge machining enhanced the machining stability, and a comparatively higher workpiece removal rate was observed with a decreased electrode wear rate. On the other hand, by increasing the discharge current, which was also verified as the most effective machining parameter in variance analysis, both workpiece removal rate and electrode wear rate values increased in both machining techniques. The experimentally calculated volumetric workpiece material removed by a discharge pulse was compared to that of a model in the literature, and they were also found to be consistent with each other.

Comparative study of the behaviour of several reinforcement materials in titanium matrix produced by Rapid Sinter Pressing Manufacturing

2022-12-27T11:02:12+01:00

Regarding titanium matrix composites (TMCs), their properties strongly depend on the reinforcement material employed for their manufacturing; this may lead to a multitude of investigations on TMCs. Considering the diverse typology of the reinforcement, six types of ceramic particles were tested in this investigation: B₄C, SiB₆, TiB₂, TiC, TiN, and BN. In order to compare their behaviour and their own influence on the properties of the TMCs, the same ratio was employed in the starting materials, 30% volume. Among the techniques for developing TMCs, a significant number of authors propose Powder Metallurgy as a favourable route. In this framework, the novel Rapid Sinter Pressing technique was employed to perform the present study, due to its flexibility, repeatability, and reproducibility, as well as short-run cycle times. The processing temperature (930 °C) was set with the intention of evaluating how the reinforcements behave differently depending on their reactivity with the Ti matrix. In this regard, the main objective of the research was to carry out a comparison on the behaviour of seven TMCs fabricated with similar operational parameters via RSP.

Microstructure and mechanical properties on friction stir processed TIG welded dissimilar joints of AA5052-H32 and AA5083-H111 alloys by grey approach

2022-12-27T11:43:45+01:00

In this investigation, the mechanical behaviour and microstructural examination of friction stir processed (FSP) Tungsten Inert Gas (TIG) welded aluminium dissimilar alloys has been studied. The research is proposed to enhance the mechanical characteristics of the aluminium alloy 5052-H32 and aluminium alloy 5083-H111 TIG FSP welded joints. Initially, the TIG welding was done to join aluminium alloy 5052-H32 and aluminium alloy 5083-H111 by employing a ER5356 filler rod. TIG welding is performed by using the following parameters: tungsten electrode diameter (2.4 mm), Current (170 A) and a shielding gas flow rate (argon) (11 l·min^-1). Secondarily, the FSP is carried out on TIG welded aluminium alloy 5052-H32 and aluminium alloy 5083-H111 by using different tool rotation speeds (850 to 1050 rpm), tool traverse speeds (24 to 32 mm·min^-1) and different number of passes (1 to 3) with a cylindrical pin less tool. The FSP parameters are designed by the Taguchi L9 array to compute the optimized parameters. The tensile strength, microhardness and % of elongation are determined for a total of nine specimens. Finally, the grey relational analysis (GRA) is employed to find out the best FSP parameter out of the set of FSP parameters. The optimal parameters of FSP are a tool rotation speed of 950 rpm, tool traverse speed of 28 mm/min and number of passes of 3. The number of passes are the most influencing factor when compared to other two FSP parameters.

TiN hard coating as a candidate reference material for surface metrology in chemistry: characterization and quantification by bulk and surface analyses techniques

2022-12-27T12:54:31+01:00

This study presents the synthesis and characterization of TiN hard coatings as a candidate reference material for surface metrology in chemistry. TiN coatings were grown on a silicon wafer with (111) orientation using dc reactive magnetron sputtering. X-ray diffraction confirms that the diffraction phase of TiN coatings is polycrystalline, electron microscopy demonstrates that the TiN coatings presents pyramidal-shaped grains ranging from sub-micrometer to nano-size scale and with an average thickness of 666 nm. According to micro Raman results, the presence of LO phonon modes confirms that the TiN coatings are crystalline in nature and no impurities are detected. The mechanical properties at the nanoscale are evaluated using resonance tracking acoustic force atomic microscopy. The chemical composition of the TiN reveals a close 1:1 atomic ratio. The ANOVA is used to evaluate the homogeneity of the TiN via a homogeneity test according to the ISO Guide 35:2017, while, regarding the chemical composition of the Ti, the Fisher’s test demonstrates that the batch can be considered as homogeneous.

Effect of surface macroroughness on the microstructure and sliding wear properties of Al2O3 + 13 wt.% TiO2 thick coatings

2022-12-27T12:16:11+01:00

ABSTRACT

Two macro-roughness patterns namely spiral grooving and diamond knurling were performed on an AISI/SAE 1045 cylindrical steel bar. Al₂O₃ + 13 wt.-% TiO₂ powder was deposited by utilizing a multi-pass torch. Microstructure, microhardness and wear resistance were analyzed. The presence of both γ-Al₂O₃ and α-Al₂O₃ throughout the coating was promoted by partially melted and un-melted particles; however, the formation of interlayers of hard α-Al₂O₃ was influenced by the re-heating during the multi-pass torch causing transformation from γ-Al₂O₃→α-Al₂O₃. Knurling pattern specimens contained less defects owe to a suitable splat accommodation thus strengthening the inter-splat anchorage. The improved sliding wear resistance was influenced by both the combination of γ-Al₂O₃ (toughness) and α-Al₂O₃ (hardness) phases and, predominantly by the reduced porosity and micro-cracks in specimens with the knurling pattern.