材料期刊网

镁-钍-锰合金在350℃,3.0公斤/毫米~2的条件下蠕变时,经过冷加工和不经过冷加工的试样具有不同形状的蠕变由线。未经冷加工的试样在恒速蠕变阶段几乎看不到的情况下即进入加速蠕变阶段,而经过冷加工的试样的恒速蠕变阶段则很长。未经过冷加工的试样在蠕变第一阶段出现明显的滑移,进入蠕变第三阶段出现多边化及显著的晶界滑动,这两个过程同时进行并相互影响可能是使恒速蠕变阶段不明显的基本原因。冷加工强化了晶体,减缓了晶界滑动的速率,从而使蠕变第二阶段显著增长。 合金在上述条件下沿晶界断裂主要是服从Zener的应力集中机构。

The creep behavior of a Mg-Th-Mn alloy at 350℃ under a constant load cor-responding to an initial stress of 3.0 kg/mm~2 has been investigated. The shape of thecreep curve of cold-worked specimens differs from that of annealed ones in that the steadycreep stage is almost absent in the latter though it is remarkable in the former. Forthe annealed specimens slip has been observed in the first stage of creep, and poly-gonization and grain boundary gliding have been shown to occur in the third stage. Thatthese processes take place simultaneously and also react with each other may be the reasonfor the absence of the steady stage of creep in annealed specimens. It is assumed thatcold-working strengthens the grains, thus slowing down the rate of grain boundary gliding. The intercrystalline fracture of this alloy is mainly due to the stress concentrationaccording to Zener's mechanism.