IMPACT OF COLD PLASTIC DEFORMATION AND THERMAL POST-TREATMENT ON THE PHYSICAL PROPERTIES OF COPPER BASED ALLOYS Al-BRONZE AND α-BRASS

The copper based alloys Al-bronze and α-brass containing each of 10wt% aluminum and zinc were prepared by casting. Afterwards, the specimens were cold-rolled with various percentages of deformation and the cold-rolled samples were aged subsequently at the varied time for four hours and temperatures ranging up to 500°C. Samples underwent characterizations by microhardness testing, electrical resistivity, optical properties, differential scanning calorimetry as well as microstructure analysis using an optical microscope. The results showed that the hardening of Cu-based alloys was taken place due to solid-solution hardening. Al addition accelerated the hardness through ageing due to the formation of various intermetallic copper aluminites into the aged alloy which was hard and brittle in nature. The resistivity decreased marginally through heat treatment due to the stage of stress relieving, recovery, precipitation coarsening as well as recrystallization and increased for arranging different intermetallics into the alloys. The microstructural study revealed that the cold rolled alloys content the different phases of elongated grain at the rolling direction. Meanwhile higher ageing temperatures at 500°C for one hour led to recrystallization and grain growth especially in pure copper and Cu-10Zn alloys.

Mechanical and Chemical Characterisation of TiN and AlTiSiN Coatings on a LPBF Processed IN718 Substrate

Wear-resistant coatings development is progressively increasing steeply due to their advantages when applied to mechanical components subjected to abrasive and destructive environments. Titanium nitride (TiN) coating is typically used to enlarge tools and components’ service life and improve their surface quality. On the other hand, AlTiSiN coating intends to be applied to more aggressive environments such as spatial satellites components exposed to solar radiation, extremely high temperatures, and random particles impact. In this work, specimens of Inconel 718 (IN718) were fabricated via laser powder bed fusion (LPBF), and physical vapour deposition (PVD)-deposited with TiN and AlTiSiN as coatings to mechanically and chemically characterise their surface. In this respect, microhardness testing and chemical analysis via glow discharge optical emission spectroscopy (GDOES) were performed. Later, roughness and wear behaviour analyses were carried out to evaluate the mechanical performance of both coatings and their surface and morphological features. The experimental observations allowed the analysis of both studied coatings by comparing them with the substrate processed via LPBF.

Wear and Corrosion Properties of Plasma Transferred Arc Ni-based Coatings Reinforced with NbC Particles

The wear and corrosion resistance of Ni-based niobium carbide (NbC) coatings were investigated via scanning electron microscopy, energy dispersive spectrometry, particle size analysis, X-ray diffraction, electrochemical polarization, electrochemicl impedance spectroscopy, digital microhardness testing and wear testing. The results showed that the substrate was mainly composed of a γ-Cr (Fe) solid solution, and the composite coating was composed of FeNi, NbC, and Ni. In addition, the hardness of the coating increased gradually with increasing NbC content. The optimal corrosion resistance and wear resistance of the coating were realized at an NbC content of 20%.

Application of MIG Welding Process of Mild Steel Wire in Additive Manufacturing

The purpose of this study is to investigate the forming characteristics of single-pass Metal Inert Gas (MIG) welding wire for multi-layer additive manufacturing parts. Influences of arc current, arc voltage, arc distances, welding speed, wire feed speed, temperatures and heat input on layer formation were analyzed. The deposition of material by MIG process is controlled by a robot (ABB) controller for constructing walls of rectangular box shape. The samples were measured with a microhardness testing and tensile testing onto the welded bead created by the additive manufacturing technique. It was found that the mechanical properties of microhardness values are between 151.70 to 155.80 HV and the tensile strength values are between 472.71 to 491.12 MPa according to transverse and longitudinal sections of the specimens.

Optimization of Maximum Tool Travel Speed for Friction Stir Welded AA-2014-T6 without Compromising the Mechanical Properties

In this study optimization of maximum travel speed that can be achieved for Friction Stir Welding of Aluminum Alloy 2014-T6 without compromising the mechanical properties was carried out. Joints were made at different travel speeds of 200, 300, 400, 500 and 600 mm/min with constant tool rotational speed of 800 rpm and tool tilt angle of 2.The samples were characterized by stereo microscopy, optical microscopy, scanning electron microscopy, Vickers microhardness testing and tensile testing. Microstructural features of as-welded samples revealed refined equiaxed grains in nugget zone and grain growth in the heat effected zone. Tensile test results showed that the tensile strength was maximum at travel speed of 500 mm/min but then decreased after further increasing the travel speed. Hardness in the nugget zones of all welds was lower than that of base material. Fractographic analysis exhibited significant variations in fracture surfaces of tensile samples. A relationship between the welding parameters and resultant heat inputs was also discussed.

Synthesis and some properties of compounds Cu2PrSb3S7 and Cu2ErSb3S7

The phase equilibrium in systems of CuSbS2 – PrSbS3 and CuSbS2 – ErSbS3 has been studied by physicochemical methods (Differential thermal analysis – DTA, X-ray diffraction phase analysis, Scanning Electron Microscopy – SEM analysis and microhardness testing) and their T-x diagrams were drawn. It was determined that both systems are quazibinary and characterized by formation of Cu2LnSb3S7 -type (Ln = Pr, Er) compounds. Cu2PrSb3S7 melts congruently at 1050 K and is the phase with unstable content. Its dissolution zone changes within concentration interval of 32-37 mole% of PrSbS3. Cu2PrSb3S7 divides the system into two sub-systems: CuSbS2-Cu2PrSb3S7 and Cu2PrSb3S7-PrSbS3. Both of sub-systems are eutectic. The coordinates of the eutectic point are like following: 15 mole % PrSbS3, T = 740 K and 50 mole % PrSbS3, T = 790 K. Cu2ErSb3S7 melts at 920 K by decomposition. At 725K between Cu2ErSb3S7 and CuSbS2 compounds in content of 15 mole % of ErSbS3 is formed eutectic balance. 4 mole % of solid solution is formed on base of CuSbS2. Both compounds are crystallized by naffildite-type structure in the form of rhombic syngonia (Cu2PrSb3S7 – a = 1.444; b = 2.146; c = 0.3995 nm; z = 4; Cu2ErSb3S7 – a = 1.430; b = 2.128; c = 0.380 nm; z = 4; stereogroup Pbnm or Pbn21).

Nanoparticles as void fillers in glass ionomer cement for enhanced physicomechanical properties

The study evaluated the addition of silver (Ag) and titanium dioxide (TiO2) nanoparticles to conventional glass ionomer cement (GIC), considering compressive strength (CS), diametral tensile strength (DTS), flexural strength (FS), and hardness. Ag and TiO2 nanoparticles were blended into the powder of a commercially available GIC restorative material at 5% (w/w). Unblended powder was used as a control. One hundred twenty samples were prepared from two study groups and one control group (n = 10). CS, DTS, and FS were evaluated using a universal testing machine, while hardness was measured by Vickers microhardness testing. The data obtained were analyzed using One-way analysis of variance and the Tukey?s test (p < 0.05). GIC containing Ag and TiO2 nanoparticles significantly improved the CS, DTS, and hardness compared to the control group (p < 0.05). However, the FS was not much affected by the addition of either of the nanoparticles (p >0.05). TiO2 blended GIC demonstrated significantly higher CS (154.20+2.38) and DTS (13.2±0.5 MPa) compared to control 117.2±1.2 MPa and 7.2 ±0.8 MPa, respectively. While Blend of GIC+Ag nanoparticles showed the highest FS (29.0±0.7 MPa). Additionally, the blend of GIC+TiO2 exhibited the highest hardness (90.4±1.1 VHN). Ag and TiO2 blended GICs might guarantee their use in occlusal or higher stress-bearing areas.

A New Microhardness Testing Method on Grating Films

The manufacturing process of large-area, high-precision gratings is a very complicated and time-consuming process. The hardness testing of grating films is an important step in the entire process. In order to simplify the manufacturing process of gratings, we have proposed a new method for testing microhardness based on tool edge indentation. Also, it unified tool adjustment and microhardness testing steps in the grating manufacturing process. First, a mathematical model of the relationship between tool load and indentation contour length is established. The model parameters were then modified using tool indentation experiments with different loads. When measured with a nanoindenter, the average hardness of the grating film was 447 MPa. The hardness value of the grating film obtained by our proposed method is almost the same as that measured by the nanoindenter, and the maximum deviation is about 2.2% of the average hardness value. The experimental results show that our proposed method can replace the microhardness test method of using a nanoindenter. Therefore, the disadvantages of using a nanoindenter to test the hardness of a grating film are avoided, such as the limited sample size, the sensitivity of the indenter to the roughness of the film and the depth of the indentation, and the accuracy of film testing, and the efficiency of grating ruling can be improved.

Taguchi Design for Heat Treatment of Rene 65 Components

Rene 65 is a nickel-based superalloy used in aerospace components such as turbine blades and disks. The microstructure in the as received condition of the superalloy consists of ~40% volume fraction of gamma prime precipitates, which gives such a high strength that thermomechanical processing is problematic. The goal of this study was to develop a heat treatment for manufacturing of Rene 65 components by changing the size distribution and volume fraction of those precipitates and lowering the strength. Gamma prime in this alloy is observed in three sizes, ranging from a few μm to tens of nm. For the design of the heat treatments, Design of Experiments (DOE) has been used; more specifically Taguchi’s L8 matrix. The four factors that are examined are cooling rate, hold temperature, hold time and cooling method to room temperature. The levels of the factors were two (high and low) with replication. Microstructures were characterized by Scanning Electron Microscopy and mechanical properties by Vickers microhardness testing.