Physical Behaviour of Thermally Affected Bronze and Brass

The physical behavior of thermally affected cast copper, aluminium bronze and brass has been studied by subjecting to heating isochronally for one hour at a range of 600°C. It shows that solid-solution hardening takes place into the Al added bronze and Zn added brass metal. Due to heating Al forms hard and brittle intermetallic of copper aluminites into bronze metal which responses some age hardening effects. The electrical conductivity of the metals increases initially through heat treatment due to stress relieving and finally decreases due to formation of intermetallic precipitates. The color of the heated samples are also studied through tristimulus color ‘L*’, ‘a*’ and ‘b*’ values which were analyzed and evaluated in MATLAB software. It is found that incorporation of Al and Zn affects the colour of cast Cu. The overall change of color occurs with increasing heating temperature due to chemical changes like oxidization, intermetallic formation, dissolution of phases, precipitation coarsening and recrsystallization. Due to change of hardness and microstructural properties of the experimental metals the sound intensity level also decreases at high heating temperature. A microstructural study confirms that the cast alloys contents the different phases of grains and bring about re-crystallized state after heating at 500°C for one hour

Influence of Aluminium and Zinc Additives on the Physical and Thermal Behaviour of Cast Copper

Role of aluminium and zinc additions on the physical and thermal behavior of cast copper are investigated. Metal casting is used in the production of bronze and brass with composition of 10wt% each Al and Zn. Cast alloys has been studied by subjecting to isochronal and isothermal ageing at various temperatures up to 500°C and different times ranging from 15 to 240 minutes respectively. Microhardness values of the differently processed alloys have been measured to understand the ageing behavior of Cu with Al and Zn addition. It is observed that hardening takes place due to solid-solution hardening. Al addition responses some age hardening behavior in the aged alloy due to formation of hard and brittle intermetallic of copper aluminites. The thermal conductivity of the alloys increases marginally through heat treatment due to stress relieving and decreases due to formation of intermetallic precipitates.  It is also found that incorporation of Al and Zn affects the absorbance properties of cast Cu. A microstructural study of the alloys reveals that the cast alloys contents the different phases of grains. It is also observed that all the alloys accomplish partially re-crystallized state after aging at 400°C for one hour

A comparative study of chemical and physical properties of copper and copper alloys affected by acidic, alkaline and saline environments

Chemical and physical behavior including corrosion performance, thermal conductivity and visual color change of the copper-based alloys brass and bronze have been studied prior and after corrosion in acidic, alkaline and saline media. The concentrations of 0.5 M H2SO4, 0.5 M NaOH and 0.5 M NaCl were used in which copper and copper-alloy samples were immersed and left to corrode at room temperature for 28 days. The experiments were performed prior and after corrosion, using conventional gravimetric measurements accompanied with measurements of thermal conductivity, microstructure and optical properties. The color change of different samples was also studied through tristimulus color parameter (L*, a* and b*) values. It is concluded that the corrosion rate of copper and copper alloys is greater in acidic than in salt and alkaline media. This is due to the extent of disruption of the passive film formed on the surfaces. In the cases of alkaline and salt media, the passive films on the surface remain stable to a large extent. Small increase of thermal conductivity takes place due to formation of a very thin film of oxide and hydroxide bonded to the surface. The environment also affects the color of copper and copper alloys by chemical changes like oxidation and formation of different intermetallics on the surfaces. A microstructural study of experimental materials confirms that corrosion after 28 days results in formation of pores on the surfaces in acidic environment, and passive film that grows thicker on the surfaces in alkaline and saline environments. Aluminum oxide that is more stable than zinc oxide causes better anti-corrosion performance and minimal color variation of bronze compared to brass, especially in acidic environment.</p

Relativistic Corrections to Nonrelativistic Effective Field Theories

In this paper we develop a formalism for studying the nonrelativistic limit of relativistic field theories in a systematic way. By introducing a simple, nonlocal field redefinition, we transform a given relativistic theory, describing a real, self-interacting scalar field, into an equivalent theory, describing a complex scalar field that encodes at each time both the original field and its conjugate momentum. Our low-energy effective theory incorporates relativistic corrections to the kinetic energy as well as the backreaction of fast-oscillating terms on the behavior of the dominant, slowly varying component of the field. Possible applications of our new approach include axion dark matter, though the methods developed here should be applicable to the low-energy limits of other field theories as well.Comment: 31pp. References added, and 3 appendices added, showing (a) how to implement the field redefinition as a canonical transformation, (b) how to develop the effective field theory using a local field redefinition, and (c) how to use a further field redefinition to compare our results with those of Mukaida, Takimoto, and Yamad

Comparison of Wear Behaviour of Commercial Tire and Bearing Pad Rubber under Dry Sliding Condition

The consequence of load and sliding distance on the performance tribology of commercially used tire and bearing pad rubber was evaluated using a pin-on-disc method. The test was carried out under ambient dry sliding conditions with load of 2.5N, at sliding velocity of 0.369 ms-1 and with varying sliding distance ranging from 110m-2650m. The results showed that the sliding distance at the fixed load affects the wear rate of the rubbers and the weight loss increased with increasing the distance for both the rubbers. Wear rate also increases almost linearly to a maximum then attain a plateau with increasing sliding distance. The tire rubber showed the higher wear and coefficient of friction due to presence of natural rubber. The worn surface was characterized by optical microscope and SEM. The results show surface with shallow grooves width and depth increased as the distance increases. Oxidative wear was found to be the predominant mechanisms in the dry sliding

Effect of Nanoclay on Thermal Properties of Polylacticacid-Kenaf Hybrid Bio-composite

An alternative composite material which is a mixture of bio-fiber with nano filler and polymer known as hybrid bio-composite has become a state of the art in composite research and development. The hybrid bio-composite has been widely studied with different combinations for the application of secondary structure in automotive industry, packaging, aerospace, sports, armour proucts and others. The availability of natural fiber (such as kenaf fiber) makes the hybrid bio-composite competetively lower cost and feasible to be produced industrially for wide range of applications. The main objectives of this paper are to fabricate and the effect of nanoclay on thermal properties of hybrid bio-composite. A comprehensive database was developed to determine the thermal property of PLA, PLA-20KF-3Clay, PLA-20KF-5Clay and PLA-20KF-7Clay. Three point bend Dynamic mechanical analysis (DMA) tests were carried out on standard specimens at temperature ranging from -900C to 1000C whereas frequency was 1Hz. The result revealed that with addition of nanoclay glass transition temperature (Tg) increased 50C. The storage modulus (E’), loss modulus (E”) and damping (tanδ) also increased with addition of nanoclay which is an indication of better thermal properties

Fabrication of biodegradable composite – an implication of plasticizer

This paper aims on the fabrication of fully biodegradable composite with the addition of plasticizer. For the fabrication of biodegradable composite, a twin screw extruder was used which provides a good blending of matrix, fiber and plasticizer. The percentage is varied from 5% to 40% for fiber and for plasticizer it is 5% to 20%. Higher percentage of plasticizer shows more difficulty during fabrication process of bio-composite. The results also showed that the addition of plasticizer reduces the melting and glass transition temperature of the composite which affects the processing parameter such as, temperature of different zones, rotation of the extruder screw, feed rate and production rate of the extruder. This paper also discussed on the suitable processing parameters for production of plasticized biodegradable composite

Electrochemical Corrosion Properties of Ternary Al and Quaternary Zr Added Bell Metal in 0.1M NaCl Solution

The electrochemical corrosion property of ternary Al and quaternary Zr added Bell metal in 0.1M Sodium Chloride solution has been experimentally conducted at room temperature. Electrochemical impedance spectroscopy (EIS) method and Potentiodynamic polarization technique are used to carry out the electrochemical investigation. Microhardness test is also conducted for all three alloys and it reveals that Al addition increases the hardness of bell metal due to the formation of different intermetallic precipitates of Cu and Al. Optical Micrograph as well as Scanning Electron Micrograph have also been studied to characterize their surface condition. It is found that Zr addition refines the grain structure of the alloy and results in increase of hardness. The EIS study reveals that the corrosion resistance is seem to be augmented with the addition of ternary Al and quaternary Zr to bell metal. The potentiodynamic polarization curves disclose that both ternary Al added and quaternary Zr added alloy show better corrosion performance than the base bell metal alloy due to the formation of stable aluminium oxide film. The currentdensity (Icorr) of base bell metal showed higher value than both ternary Al added and quaternary Zr added bell metal alloys. The corrosion potential (Ecorr) and the open circuit potential (OCP) were seen to be moved to the more positive direction for the Al and Zr added alloys. Microstructure and SEM study of the alloys after corrosion revealed a formation of an oxide film on the surface of the ternary A and quaternary Zr added alloys, the probable cause of which is the presence of Al in the respective alloys

True Stress-Strain Behavior of Al-based Cast Automotive Alloy Under Different Ageing Conditions and the Effect of Trace Zr

A thorough investigation has been carried out on the Al-12Si-1Mg-1Cu-1Ni automotive alloy considering different properties, specially mechanical properties associated with true stress and true strain with Zr addition of trace amount. A commercially available piston is melted to produce the alloy, and trace amount of Zr is added to make another. The base alloy along with the Zr added alloy had been applied to homogenization, solution treatment, quenching, and ageing in order to get the age-hardening response. The alloys have been heat-treated at 25 ºC, 200 ºC, and 300 ºC, respectively, for four hours for attaining the under, peak and over-aged states, respectively. During ageing, Al2Cu and Mg2Si phases are formed in the aluminium matrix leading to peak-aged strength, which is reduced at over-aged state because of coarsening of precipitation and recrystallizing, shown by the tensile and hardness properties. When Zr is added to the alloy, Al3Zr phases appear while casting and heat-treatment, resisting the drop of strength at over-aged state. It is visible in the stress-strain diagram that at over-aged conditions, the alloy with trace Zr shows improved strength and ductility. In the micrographs of Zr added alloy, finer distributed grains are visible through the grain refinement of Zr, which also prevents recrystallization at over-aged conditions. The homogeneity of the grains as a result of the Zr addition's microstructural change was further confirmed by fractography. It is clear that adding Zr to such alloys does not greatly increase their strength, but it does restrict the declining of strength by preventing the production of thermally stable Al3Zr precipitates, which coarsens the resisting behavior of various intermetallics in the thermally damaged alloy