OSO204 鉛フリーはんだにおけるクリープ疲労き裂進展のEBSDによる研究(放射光およびEBSD法による材料評価,OS-2 回折法による材料評価)

Abstract

Crack propagation tests of lead-free solder were conducted using center-notched plates under cyclic tension-compression of three stress waveforms: pp waveform having fast loading and unloading, cch waveform with tension and compression holds, cph waveform having tension hold. Fatigue and creep components of the J integral were evaluated from the load displacements relations using simple estimates. For fatigue loading of pp waveform, the crack propagation rate was expressed as a power function of the fatigue J integral. The creep component due to the hold time greatly accelerated the crack propagation rate. The creep crack propagation rate was expressed as a power function of the creep J integral for each case of cph and cch waveforms. The crack propagation rate for cph waveform was higher than that for cch waveform. SEM observation after the removal of the surface layer showed many tiny cracks in the vicinity of the main crack for cph waveform, suggesting crack propagation acceleration. The grain fragmentation was observed near the crack by EBSD and its amount increased with increasing crack propagation rate.