Issue 35

A. Pawełek et alii, Frattura ed Integrità Strutturale, 35 (2016) 21-30; DOI: 10.3221/IGF-ESIS.35.03 28 solution for sensor-sample contact at elevated temperatures) and the preparation of the Mg4Li4Zn alloys, following the indications of work [19], so that the plastic instability related to the PL phenomenon could be observed. (a) (b) (c) (d) (e) (f) Figure 10 : The AE behavior and the external stresses of tensile tested Mg4Li4Zn alloy: (a) at room temperature and (b) at 200ºC; (c, d) corresponding SEM pictures of fracture, (e, f) SEM images of fracture at 400ºC. C ONCLUSIONS he work describes the preliminary research of the influence of plastic instabilities (PL effect, twinning, shear banding) on the fracture of Mg-Li based alloys in tensile and compression tests at elevated temperatures with the unique application of Acoustic Emission technique. It seems that the following conclusions are quite reasonable: 1. The fractures of tensile tested Mg4Li5Al alloys at elevated temperatures are initially of transcrystalline character but the transition to intergranular type starts already from 150°C, while at 200°C the fracture is of intercrystalline character already. T