Improvement of Al-6061 alloys mechanical properties by controlling processing parameters
— this paper discusses the effect of casting processing parameter on the mechanical properties of Aluminum alloy 6061 companied with Al 2 O 3 and Si C P. The specimens were poured in two different mold types one of steel and the other of graphite. These two types have a wide range of cooling rate; steel has fast cooling rate whereas graphite has slow one. In order to investigate this effect, and the alloying elements participation the specimens were taken from three different positions in the mold; top, middle and bottom. The mechanical wear, hardness and microstructure examination were performed. The results showed that wear rate and hardness increase in case of specimen poured in steel mold. This increasing due to fast cooling rate which make refining of the grain size of aluminum alloys. Whereas, their mechanical properties decreased when using graphite molds. In contrast of this result, ductility is increased. This is attributed to that graphite has slow cooling rate (heat dissipate is low) which make enlargement to the grain size of aluminum alloy and the graphite is also solid lubricate playing as interactive lubricate which is main reason to decrease the wear rate.
Composite Materials Based on EN AW-Al Cu4Mg1(A) Aluminum Alloy Reinforced with the Ti(C,N) Ceramic Particles
Investigations of composite materials based on EN AW-Al Cu4Mg1(A) aluminum alloy reinforced with the Ti(C,N) particles with various weight ratios of 5, 10, and 15% are presented. Powders of the starting materials were mixed in the laboratory vibratory ball mill to acquire the uniform distribution of reinforcement particles in the matrix material. The components were initially compacted at cold state in a die with the diameter of ∅ 26 mm in the laboratory vertical unidirectional press – with a capacity of 350 kN. The obtained P/M compacts were heated to a temperature of 480÷500°C and finally extruded – with the extrusion pressure of 500 kN. Bars with a diameter of 8 mm were obtained as the end product. Based on the microstructural examinations of the obtained composite materials, the uniform distribution of the reinforcing particles in the aluminum matrix was revealed. Hardness tests, tensile tests and the ultimate compressive strength tests made it possible demonstrate that all these properties change along with the reinforcing particles concentration change.
Coated-wire electrodes containing polymer immobilized ionophores blended with poly(vinyl chloride).
Polymers containing covalently attached 18-crown-6 or 2.2.2 cryptand units were incorporated into plasticized PVC membranes and the composite membranes were examined as potassium ion sensor elements. Ionophores were linked to carboxy-PVC and to poly(acrylic acid) via amide linkages to an alkyl spacer unit. Coated-wire electrodes (CWEs) from the immobilized ionophores gave acceptable responses, but conventional ion-selective membrane electrodes (ISEs) prepared by solvent casting were inactive. Dip-cast membranes did give active ISEs. Potassium electrode performance was independent of the loading of the ionophore within the acrylate support polymer, but depended upon the spacer length. Ion selectivity varied with the ionophore loading within the support polymer. Selectivity is a composite of the ionophore selectivity and ion-exchange interactions with the acrylate backbone, giving selectivities akin to carboxylate substituted crown ethers, notably enhanced monovalent/divalent ion discrimination relative to the ionophore in solution. Polymer immobilization extended the lifetime of active electrodes.