3004铝合金“反常”锯齿屈服现象的研究

在应变速率为5.56×10^-5s^-1—5.56×10^-3s^-1的范围内，在不同温度下(从223K至773K)，对3004铝合金进行系列拉伸试验，探索其锯齿屈服规律；通过激活能的计算、内耗研究、微观组织观察和能谱分析，探讨锯齿屈服的机理与物理本质.结果表明，3004铝合金在形变过程中会出现动态应变时效现象；发现了一种“反常”的锯齿屈服现象：在出现锯齿屈服的温区内，存在锯齿屈服临界应变量转变温度T_t， 关键词： 动态应变时效 锯齿屈服 铝合金 内耗

Study of an anomalous serrated yielding phenomenon in 3004 aluminum alloy

The serrated yielding in metals and alloys is an important and interesting physical phenomenon. No. 3004 aluminum alloy has been subjected to tension test in a range of strain rates 5.56×10^-5s^-1—5.56×10^-3s^-1 and temperatures 223K—773K to investigate the ordinary rules of serrated yielding phenomenon. The micro-mechanism and physical essence of serrated yielding of the material has been studied by means of activation energy, internal friction and microstructure. The results show that the serrated yielding phenomenon is associated with the dynamic strain aging process. In the serrated yielding temperature region, an anomalous serrated yielding phenomenon was found. Within this temperature region, a critical transition temperature T_t exists. The critical plastic strain for the onset of serrations has a negative or positive temperature coefficient within the temperature region lower or higher than T_t, respectively. The former is the normal serrated yielding and the latter is called “anomalous”. It is believed that the process at the temperature region lower than T_t is controlled by the interaction between Mg solute atom atmosphere and dislocations. In the positive coefficient region, the aggregation of Mg atoms and precipitation of second phase decrease the effective amount of Mg atoms in solid solution and leads to the appearance of a positive temperature coefficient of the critical plastic strain for the onset of serrations.