Issue 35

W. Ozgowicz et alii, Frattura ed Integrità Strutturale, 35 (2016) 11-20; DOI: 10.3221/IGF-ESIS.35.02 16 stretched at the temperature of 250  C is after continuous casting (Fig.6) much higher than after homogenizing annealing (Fig.7). The activity of the AE signal has also been observed to increase with elevated temperature of deformation (Fig.8). Nevertheless, the frequency of oscillation of the stresses recorded on the curves σ-ε and the frequency of events do not indicate any explicit correlation in the investigated experimental conditions. The highest number of events (or mean energy of the events of AE) was recorded in the case of the CuSn6P alloy cast continuously (or homogenizingly annealed) at the temperature of stretching, amounting in the range 250÷350  C with mean value of the energy of the events of about 66 nJ. The results of metallographic observation of the investigated bronze being deformed at the temperature of 150÷250  C have been presented in the microphotographs (Fig.9). It has been found that up to the temperature T E of about 250  C, bronze displays in the annealed state axially elongated grains of the solution-  with typical effect of cold work-hardening and heterogeneous plastic deformation (Fig. 9a). A distinct initiation of the process of cracking at the grain boundaries mostly in the point of contact of three grains was detected in sample stretched at a temperature of 250  C (Fig. 9b). An increase of the temperature of deformation to about 400  C, corresponding to the minimum temperature of plasticity (TMP), results in an increase of the number of intercrystalline cracks independent of the state of the investigated bronze. No. Temperature of deformation Sum of AE events Average energy of the AE events [nJ] CuSn6P after continuous casting 1 50 547 76 2 100 322 56 3 150 441 55 4 200 216 24 5 250 743 66 6 300 130 120 CuSn6P in the annealed state 1 RT 971 125 2 100 692 111 3 150 1254 140 4 200 8261 57 5 250 306 105 6 300 63 30 Table 3 : Descriptors of the analysis of the AE signals for the CuSn6P alloy. Figure 6 : Acoustic emission and stress during the deformation of CuSn6P alloy at 250  C after continuous casting.