Mechanism of 〈112〉/3 slip initiation and anisotropy of γ′ phase in CMSX-4 during creep at 750°C and 750 MPa
Mechanism of 〈112〉/3 slip initiation and anisotropy of γ′ phase in CMSX-4 during creep at 750°C and 750 MPa
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DOI：
10.1016/s0921-5093(03)00148-5
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发表时间：
2003-09
期刊：
影响因子：
6.4
通讯作者：
Qi-zhi Chen;D. Knowles
中科院分区：
文献类型：
--
作者：
Qi-zhi Chen;D. Knowles
用透射电镜结合计算机模拟显微图像，对CMSX-4单晶在750 ℃、750 MPa下进行的拉伸蠕变试验中的[ 1 <$36]、[001]、[011]和[111]四种近似取向的蠕变缺陷进行了仔细的鉴定。取得了一系列的研究成果。(i)结果表明，γ′相的<$112 <$/3滑移主要是两个不同Burgers矢量的<$110 <$/2位错在γ/γ′界面处相遇，并在界面处俘获产物<$112 <$/6部分位错。(ii)在750°C和750 MPa条件下，{111}-112滑移系的选择性对Schmid因子敏感。各向异性的原因是高应力{111}<$112 <$/3滑移系在[ 1 <$36]、[001]和[011]方向上的分解剪应力正好在γ′相中<$112 <$/3断层的临界分解剪应力附近，估计为<$300 MPa。因此，RSS的轻微减小可以关闭{111} Δ 112 Δ滑移系统的操作，反之亦然。(iii){111}<$110滑移系的活化是γ′颗粒中产生<$112 <$/3断层的必要因素，但不是充分因素。作用于{111}<$112 <$/3滑移系上的RSSs控制着<$112 <$/3滑移的运行和超晶格层错的密度。
Creep deformation defects from tensile creep tests carried out at 750°C under 750 MPa in the approximate orientations [ 1 ̄ 3 6], [001], [011] and [111] for CMSX-4 single crystals have been identified carefully, using transmission electron microscope combined with computer simulated microimages. A series of results have been obtained. (i) It was confirmed that 〈112〉/3 slip in γ′ phase mainly involved the reaction and dissociation of two 〈110〉/2 dislocations which had different Burgers vectors and met at the γ/γ′ interfaces where the product 〈112〉/6 partials were trapped. (ii) At 750°C and 750 MPa, the selectivity among {111}〈112〉 slip systems was sensitive to Schmid factors. The reason for the anisotropy was that the resolved shear stress of highly stressed {111}〈112〉 slip systems in the [ 1 ̄ 3 6], [001] and [011] orientations were just around the critical resolved shear stress of 〈112〉/3 faulting in γ′ phase which was estimated to be ∼300 MPa. Hence, a slight decrease of a RSS could switch off the operation of a {111}〈112〉 slip system, or vice versa. (iii) The activation of {111}〈110〉 slip systems was a necessary but not sufficient factor of initiating 〈112〉/3 faulting in the γ′ particles. The operation of 〈112〉/3 slip and density of superlattice stacking faults were controlled by the RSSs acting on those {111}〈112〉 slip systems.