Plastic deformation of single crystals of Pt3Al with the L12 structure having a far Al-rich off-stoichiometric composition of Pt-29at.%Al
Plastic deformation of single crystals of Pt3Al with the L12 structure having a far Al-rich off-stoichiometric composition of Pt-29at.%Al
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DOI：
10.1080/14786435.2014.885142
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发表时间：
2014-04
影响因子：
1.6
通讯作者：
N. Okamoto;Y. Hasegawa;H. Inui
中科院分区：
文献类型：
--
作者：
N. Okamoto;Y. Hasegawa;H. Inui
本文研究了非化学计量成分为Pt3Al的Pt3Al单晶在77-1273K压缩下的塑性变形行为。与Pt3Al单晶相比，L12相在Pt3Al的组成为Pt29at.%Al时至少稳定在70K以下，而Pt3Al单晶的非化学计量组成为Pt3Al时，在(0 0 1)和(1 1 1)上沿〈1 1 0〉发生滑移，滑移On(0 0 1)是主要滑移系，除[0 0 1]附近较窄的取向区外，大多数晶体取向的临界分辨剪应力(CRSS值)都很小。在低温下，(0 0 1)和(1 1 1)面上滑移的CRSSs均随温度的升高而迅速下降，且由于固溶硬化效应，Pt2 9at.%Al的CRSSs均高于Pt2 7at.%Al。对于(0 0 1)和(1 1 1)滑移面，具有b(Burgers矢量)==的位错分解成两个共线超偏振子，b=1/2被相应滑移面上的APB(反相边界)隔开。低温下(111)面上滑移的CRSS的大的负温度依赖性不是由于b=1/3〈1 1 2〉的超晶格本征堆积错耦合超微子的运动所致，而是由于Peierls机制作用于具有非平面核心结构的超晶格内禀堆积断层耦合超微子.在(0 0 1)上滑动的APB耦合超偏微子的核心被认为是平面的，因此，在(0 0 1)上滑动的CRSS具有很大的负温度依赖性，这是由于非化学计量成分产生的固溶效应。
The plastic deformation behaviour of single crystals of Pt3Al with the L12 structure having an off-stoichiometric composition of Pt-29at.%Al has been investigated in compression from 77 to 1273 K. The L12 phase is stable at least down to 70 K at a composition of Pt-29at.%Al, in contrast to Pt-27at.%Al, in which transformation into a tetragonal phase occurs at around 220 K. Slip occurs along 〈1 1 0〉 both on (0 0 1) and on (1 1 1) with slip on (0 0 1) being the primary slip system that operates at considerably smaller critical resolved shear stress (CRSS) values in most crystal orientations, except for a narrow orientation region close to [0 0 1]. The CRSSs for both slip on (0 0 1) and (1 1 1) decrease rapidly with increasing temperature at low temperatures, and they are both higher for Pt-29at.%Al than for Pt-27at.%Al due to solid-solution hardening effects. Dislocations with b (Burgers vector) = dissociate into two collinear superpartials with b = 1/2 separated by an APB (anti-phase boundary) on the corresponding slip plane for both slip on (0 0 1) and (1 1 1). The large negative temperature dependence of CRSS for slip on (1 1 1) at low temperatures is not due to the motion of superlattice intrinsic stacking fault (SISF)-coupled superpartials with b = 1/3〈1 1 2〉 but is due to the Peierls mechanism acting on APB-coupled superpartials with a non-planar core structure. The core of APB-coupled superpartials gliding on (0 0 1) is considered to be planar, and hence, the large negative temperature dependence of CRSS for slip on (0 0 1) is due to solid-solution effects arising from the off-stoichiometric composition.