種々のマグネシウム合金における AE によるき裂進展検出と破壊じん性評価

抄録

  The simple method for evaluation of fracture toughness in Mg alloys was examined by AE. In this study, fracture toughness (K_IAE) in AZ31 (Mg-9Al-1Zn), AZ91 (Mg-9Al-1Zn), and LA141 (Mg-14Li-1Al) was investigated. Specimens (L-S, T-S) were machined from as-rolled AZ31, LA141, and as-cast AZ91. Four-point-bending tests were conducted according to ASTM E-399 with AE measurement, and the crack pass was observed by microscope during the testing. K_IC was supposed to be the value of K_I when the crack initiates from the tip of the pre-crack. K_IAE was defined as the value of K_I when the RMS voltage of AE indicated the maximum value before ultimate load. The crack propagation was observed by microscope at the time of RMS peak. The values of K_IAE were 12.4-15.0 (AZ31), 11.5-11.7 (AZ91), and 24.7-28.0 (LA141) [MPa m^1/2]. Compared with reference data, the fracture toughness in Mg alloys estimated by K_IAE was adequate. The possibility of the simple method for evaluation of fracture toughness in Mg alloys by AE was demonstrated.