等温模压对AZ81和AZ81E镁合金组织织构的影响

Effect of isothermal compression on microstructure texture of AZ81 and AZ81E magnesium alloys

在380℃,应变速率为0.03 s-1的变形条件下,对AZ81及AZ81E镁合金进行不同变形量的模压试验。通过XRD、SEM及EBSD对微观组织织构进行测定,分析了不同变形程度下挤压铸造AZ81和AZ81E镁合金形变机制。结果表明,随着变形量增大,晶粒尺寸明显细化并趋于一致,合金的晶粒取向发生了明显的转动。AZ81合金的(10 10)、(11 20)和(11 22)晶面在模压过程出现择优取向;在变形量超过40%后,合金内出现少量弥散的絮状β-Mg17Al12相动态析出;在60%变形量时基本为完全动态再结晶组织,(0001)基面织构强度明显增加,并逐渐趋于与压缩轴成90°方向。稀土元素RE的加入,合金的(10 10)、(11 20)、(1122)和(20 21)晶面在模压过程中出现了不同的择优取向,稀土相从离散态转变为带条状分布,形态由粗大针状转化为细化的颗粒状;(0001)基面的织构取向增大,在40%变形量时提前完成动态再结晶;变形量继续增大时,(0001)基面与压缩轴偏转一定角度,基面织构出现显著弱化,晶粒开始破碎并形成明显的带状形貌。

Die pressing test of AZ81 and AZ81 E magnesium alloys at the temperature of 380 ~C and 0. 03 s-lstrain rate was investigated. Deformation mechanisms in the process of compressing were analyzed by XRD, SEM and EBSD technigue. The results show that with increasing deformation, grains of the alloys are refined and well-proportioned. Furthermore, apparent rotation of the grain orientation of the alloys occurs. The crystal planes （ 10 TO ）, （ 11 20 ） and （ 11 22 ） of the AZ81 alloy present different preferred orientation during compressing. A small amount of floeeulent [3-Mgt7 All2 phase is dynamically precipitated when the deformation exceeds 40% , and completely dynamic reerystallization occurs when deformation is 60%. The texture strength of（0001 ）base plane dramatically increases, and it is tending to form the angle of 90° with the compression axis. With the addition of RE, the discrete distribution of the rare earth phase becomes strip distribution, and the thick needle-like phases change to refined granular shape. The crystal planes（ 10 10） , （11 0）, （ 11 22） and （20 21 ） of the alloy also show their preferred orientation in the process of compressing. The orientation of （0001） base plane increases and it completes dynamic reerystallization under the deformation of 40% , and with further increasing deformation, the （0001） base plane moves to a certain angle with compression axis, the texture of the base plane turns to be obviously reduced, and the grains start to be broken to form an obvious banding morphology.