تاثير نسبتهاي مختلف Ni:Fe و نوع عمليات حرارتي بر ريزساختار و خواص مكانيكي آلياژهاي برنز آلومينيوم ريختگي

Effect of Different Ratios of Ni:Fe and Different kinds of Heat Treatments on Microstructures and Mechanical Properties of Cast Aluminum Bronzes

In this study the effect of different amounts of Ni: Fe ratios and different kinds of heat treatments on the microstructure and mechanical properties of cast Ni-aluminum bronzes were investigated. In this way two heat treatable alloys with the same aluminum content (10.2,10.3 wt%) but with Ni:Fe>l which result lamellar k phase (alloy 1) and Ni:Fe <1 which result nodular k phase (alloy 2) and a single phase alloy with 8 wt%Al and Ni:Fe <1 (alloy 3) were produced. Tension and impact test samples were made according to the standard of the British Tension Machine of tensometer and ASTM E23. The samples of heat treatable alloys (alloy I, 2) were maintained at 950 °C for 1 hour then water quenched and were tempered at 300, 400, 500 and 650 °C for 30 minuets. Alloy 3 samples were homogenized at 700 °C for 2 ana 6 hours. Tension, impact, hardness and metallographic tests by optical microscope and SEM were done and fracture surfaces were investigated too. Mechanical properties and microstructures of alloys 1 and 2 were compared to each other for studying me effects of Ni: Fe ratio and also morphology of the k phase. For investigating the effect of aluminum contents on mechanical properties, alloys 2 and 3 were compared too. Results snowed that alloy 2 in as-cast condition with nodular k phase has better mechanical properties than alloy 1, which has lamellar k phase. Increasing the aluminum content leads to increase the tensile strength, hardness, and decrease toughness and elongation properties. In addition, to investigate the effect of heat treatment on properties and microstructures of the alloys, the quenched, quenched and tempered conditions were compared. Effect of homogenizing on mechanical properties and microstructure of alloy 3 was studied too. Results showed that increasing homogenizing time decreases the tensile strength and hardness and also increases the elongation.