In situ study of structural integrity of low transformation temperature (LTT)-welds
In situ study of structural integrity of low transformation temperature (LTT)-welds
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DOI：
10.1016/j.msea.2011.03.091
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发表时间：
2011-06-25
期刊：
影响因子：
6.4
通讯作者：
Hofmann, M.
中科院分区：
文献类型：
--
作者：
Altenkirch, J.;Gibmeier, J.;Hofmann, M.
本文讨论了焊缝残余应变在弹性和弹塑性区受静态和准循环横向拉伸载荷作用时的稳定性。测试焊缝与具有10重量% Cr和从8至12重量%变化的Ni含量的低转变温度焊接填充材料接合。用中子衍射法测量了（1）焊接引起的、（2）分步拉伸加载叠加引起的和（3）卸载后熔合区马氏体α ′相和奥氏体γ相以及热影响区和母材铁素体α相的残余晶格应变。熔合区中的残余奥氏体的量随着Ni含量的增加而增加，但由于应力诱导马氏体的形成，残余奥氏体的量随着载荷水平的增加而减少。在焊态条件下，横向宏观残余晶格应变被发现在每个焊缝的熔合区处于低压缩状态，而热影响区处于拉伸状态。局部塑性变形的γ-相作为在拉伸载荷期间屈服的结果，结合相分数的变化导致在熔合区中的宏观压缩增加。热影响区屈服强度的降低导致塑性变形和相当大的压缩位移。与横焊缝分布的中子衍射干涉线的硬度和半高宽的比较支持的假设的塑性变形的γ-和α-相在熔合区和热影响区，分别，而在熔合区的α-相内的弹性制度只强调。微观结构的观察，以及测量的本地γ相分数通过实验室X射线衍射在熔合区加强这些意见。(C)2011 Elsevier B. V.保留所有权利。
We discuss the stability of weld residual strain under static and quasi cyclic transverse tensile loading in the elastic and elastic-plastic region. The test welds were joined with low transformation temperature weld filler materials with 10 wt% Cr and varying Ni-content from 8 to 12 wt%. Using neutron diffraction the residual lattice strain in the martensitic alpha'- and austenitic gamma-phase in the fusion zone as well as the ferritic alpha-phase in the heat affected zone and base metal as (1) induced by welding, (2) superimposed by stepwise tensile loading and (3) after unloading was measured. The amount of retained austenite in the fusion zone increases with increasing Ni-content, but it decreases with increasing load level due to stress induced martensite formation. In the as-welded condition the transverse macroscopic residual lattice strain was found to be in low compression in the fusion zone in each weld, while the heat affected zone was in tension. Local plastic deformation of the gamma-phase as a result of yielding during tensile loading in combination with the change in phase fraction resulted in increased macroscopic compression in the fusion zone. The reduced yield strength in the heat affected zone resulted in plastic deformation and a considerable shift into compression. Comparison with the cross weld distribution of the hardness and FWHM of the neutron diffraction interference lines supported the assumption of plastic deformation of the gamma- and alpha-phase in the fusion and heat affected zone, respectively, while the alpha-phase in the fusion zone was stressed within the elastic regime only. Microstructural observations as well as measurement of the local gamma-phase fraction by means of laboratory X-ray diffraction in the fusion zone strengthen these observations. (C) 2011 Elsevier B.V. All rights reserved.