2ppmNaを含むAl-5%Mg合金の高温延性に及ぼすひずみ速度の影響 Effect of strain rate on hot ductility in Al-5mass%Mg alloys containing 2ppm of sodium
An impact tensile test was performed by means of the split-Hopkinson bar method to clarify the influence of strain rate on high temperature embrittlement in Al–5%Mg alloys containing traces of sodium. When the specimen was tested at a strain rate of 500 s<sup>−1</sup>, the hot ductility of the Al–5%Mg–2 ppm Na alloy decreased with increasing testing temperature, and the recovery of the ductility above 400°C was not identified. As a result of the impact test, the temperature lowering the hot ductility shifted to higher temperature in comparison with the quasi static test. Intergranular fracture was observed around 300°C in both the quasi static test and the impact test. However, area fraction of the intergranular fracture decreased in the impact test around 300°C. Observation of intergranular fracture surfaces revealed that a number of intergranular dimples were observed at grain boundary after the quasi static test, while the ledge patterns were observed at grain boundary after the impact test. It was also clarified that the high temperature embrittlement was suppressed by 200 ppm of bismuth addition below 400°C even when the specimen was deformed at high strain rate of 500 s<sup>−1</sup>.
軽金属 57(1), 25-29, 2007-01-30
The Japan Institute of Light Metals