Effect of heat treatment on internal friction in ECAP processed commercial pure Mg
Effect of heat treatment on internal friction in ECAP processed commercial pure Mg
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DOI：
10.1016/j.jallcom.2012.09.040
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发表时间：
2013-02
影响因子：
6.2
通讯作者：
G. Fan;M. Zheng;X. Hu;Chao Xu;K. Wu;I. Golovin
中科院分区：
文献类型：
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作者：
G. Fan;M. Zheng;X. Hu;Chao Xu;K. Wu;I. Golovin
采用等通道转角挤压法制备了细晶工业纯镁。对ECAP处理后的样品进行了热处理，以改变其位错密度、晶粒度和晶界等微观结构，并用动态力学分析仪(DMA)详细研究了它们对室温和高温内耗的影响。ECAP处理的纯镁合金具有较高的内耗应变无关值，热处理后由于可动位错的减少，内耗应变无关值降低，而应变相关部分由于晶粒度较大而明显增大。在测量内耗随温度变化的过程中，观察到三个内耗峰。100-200℃附近的低温峰被认为是由热激活晶界弛豫引起的，与单个弛豫时间的德拜峰相比，它明显展宽。研究了该峰的激活能和驰豫时间分布随晶粒度的变化规律。在200-350℃温度范围内的另外两个峰与频率无关，并与一些不可逆的结构转变有关，它们被认为与再结晶有关。
Fine-grained commercial pure Mg was prepared by equal channel angular pressing. Heat treatments were carried out on ECAP processed samples to modify the microstructures, such as the density of dislocation, grain size and grain boundary, and their effects on internal friction at room and elevated temperatures have been studied in detail by dynamic mechanical analyzer (DMA). The ECAP processed pure Mg shows a high value of strain independence of internal friction, which is reduced after heat treatment due to the decrease of mobile dislocations, while the strain dependent part obviously increases owing to the larger grain size. Three internal friction peaks are observed during the measurements of temperature dependence of internal friction. The low temperature peak around 100–200°C is considered to be caused by thermally activated grain boundary relaxation, and it is obviously broadened compared with a Debye peak for a single relaxation time. The changes of activation energy and relaxation time distribution of this peak with an increase in grain size were also studied. The other two peaks at the temperature range of 200–350°C are frequency independent and associated with some irreversible structural transformation, they are considered to be related to the recrystallization.