In the present investigation, acoustic emission (AE) technique has been used to study the effect of variation in strain rate on AE signals during tensile deformation of α-brass. Tensile tests have been carried out at four different strain rates, i.e. 3·33×10−4, 6·66×10−4, 1·33×10−3 and 2×10−3 s−1 with simultaneous monitoring of AE parameters. Results indicated that the intensity of AE signals increased with increase in strain rate, which had been attributed to the combined effect of dislocation motion and twinning. Optical microscopy results of deformed samples showed an increase in twin density, i.e. the number of twins per unit area with that of strain rate, which had a profound effect on AE cumulative counts. The fracture surface analysis of deformed sample by field emission scanning electron microscopy showed a transition from ductile to brittle behaviour with increase in the value of strain rate.

j m a t e r r e s t e c h n o l . 2 0 1 5;4(2):171-179 w w w . j m r t . c o m . b r Microstructure Tensile strength Grain refinement Mechanical properties Acoustic emission a b s t r a c t In the present investigation, the effect of Al-5Ti-1B grain refiner on the microstructure, mechanical properties and acoustic emission characteristics of Al 5052 aluminium alloy have been studied. Microstructural analysis showed the presence of primary ␣ solid solution.No Al-Mg phase was found to be formed due to the presence of magnesium in the solid solution. The results indicated that the addition of Al-5Ti-1B grain refiner into the alloy caused a significant improvement in ultimate tensile strength (UTS) and elongation values from 114 MPa and 7.8% to 185 MPa and 18% respectively. The main mechanisms behind this improvement were found to be due to the grain refinement during solidification and segregation of Ti at primary ␣ grain boundaries. Acoustic emission (AE) results indicated that intensity of AE signals increased with increase in Al-5Ti-1B master alloy content, which had been attributed to the combined effect of dislocation motion and grain refinement. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analysis were used to study the microstructure and fracture surfaces of the samples.

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