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首页> 外文学位 >Fatigue crack growth in welded aluminum-lithium-copper alloy 2095 (Weldalite(TM) 049).
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Fatigue crack growth in welded aluminum-lithium-copper alloy 2095 (Weldalite(TM) 049).

机译：焊接的铝-锂-铜合金2095（Weldalite TM 049）中的疲劳裂纹扩展。

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摘要

An investigation of the effects of welding on the mechanical and fatigue crack growth (FCG) properties, as well as the microstructure of the Al-Li-Cu alloy 2095 (heat treated to the T8 temper condition) was undertaken. The material concerned is a light weight, ultra-high strength aluminum alloy targeted for cryogenic and other aerospace applications. FCG tests were performed in Laboratory air on specimens prepared from the base metal (BM), heat affected zone (HAZ), and weld metal (WM). Microstructural characterization was performed using optical microscopy, transmission electron microscopy (TEM), and high resolution electron microscopy. Electron probe microanalysis was used to study segregation of solutes while the fatigue fractured surfaces were studied on the scanning electron microscope (SEM). The texture was deduced from the TEM foils and the residual stress distribution was examined by the X-ray diffraction technique. The microstructure of the BM exhibited partially recrystallized grains, a sub-grain structure, precipitation of T{dollar}sb1{dollar} (Al{dollar}sb2{dollar}CuLi), {dollar}deltaspprime{dollar} (Al{dollar}sb3{dollar}Li), {dollar}Thetaspprime{dollar} (Al{dollar}sb2{dollar}Cu), {dollar}Theta{dollar} (Al{dollar}sb2{dollar}Cu), and a new needle-like phase on {dollar}{lcub}{dollar}110{dollar}{rcub}{dollar} planes. The HAZ showed recrystallization, grain growth, dissolution of T{dollar}sb1{dollar}, reprecipitation of {dollar}deltaspprime{dollar} and of formation {dollar}delta{dollar} (AlLi). In the WM, complex intermetallics were precipitated in the interdendritic regions. WM TEM specimens prepared by ion milling showed a marked precipitation of a T{dollar}sb1{dollar}-like phase. A series of fine pores lined the fusion line (FL). Tensile failure of the weldments occurred consistently at the FL--a factor attributable to the FL pores. The hardness was lowest in the weld metal and showed maxima and minima in the HAZ. The BM had a crystallographic texture dominated by the {dollar}{lcub}{dollar}112{dollar}{rcub}langle{dollar}111{dollar}rangle{dollar} type, a feature which accounted for the 22{dollar}spcirc{dollar} deviation in the fatigue crack profile and the crystallographic shear micromechanism of FCG observed in this deviated region. A high compressive residual stress was determined at the notch tips of the WM specimens, leading to a lower FCG rate. FCG in the HAZ showed a marked dependence on {dollar}Delta{dollar}K and was influenced by the proximity of the HAZ to the FL.; Mathematical relationships between the weld thermal cycle and the HAZ hardness, and a conceptual model, relating the crack profile to the orientation of the close packed planes in a textured material, were developed.
机译：进行了焊接对机械和疲劳裂纹扩展（FCG）性能以及Al-Li-Cu合金2095的微观结构（热处理至T8回火条件）的影响的研究。所涉及的材料是用于超低温和其他航空航天应用的轻质超高强度铝合金。 FCG测试是在实验室空气中对由贱金属（BM），热影响区（HAZ）和焊缝金属（WM）制备的样品进行的。使用光学显微镜，透射电子显微镜（TEM）和高分辨率电子显微镜进行微观结构表征。电子探针显微分析用于研究溶质的偏析，而疲劳断裂表面则在扫描电子显微镜（SEM）上进行研究。从TEM箔推导出织构，并通过X射线衍射技术检查残余应力分布。 BM的微观结构显示出部分重结晶的晶粒，亚晶粒结构，T {dollar} sb1 {dollar}（Al {dollar} sb2 {dollar} CuLi），{dollar} deltaspprime {dollar}（Al {dollar} sb3 {dollar} Li），{dollar} Thetaspprime {dollar}（Al {dollar} sb2 {dollar} Cu），{dollar} Theta {dollar}（Al {dollar} sb2 {dollar} Cu）和新的针头-例如{dollar} {lcub} {dollar} 110 {dollar} {rcub} {dollar}平面上的相位。热影响区显示出重结晶，晶粒长大，T {sb1sb1 {dollar}的溶解，{dolt} deltaspprime {dollar}的再沉淀和{dollar} delta {dollar}（AlLi）的形成。在WM中，复杂的金属间化合物沉淀在树突间区域中。通过离子铣削制备的WM TEM标本显示出T {dollar} sb1 {dollar}样相的明显沉淀。熔合线（FL）衬有一系列细孔。焊缝的拉伸破坏在FL处持续发生-这是FL孔的原因。硬度在焊缝金属中最低，在HAZ中显示最大值和最小值。 BM具有由{dollar} {lcub} {dollar} 112 {dollar} {rcub} langle {dollar} 111 {dollar} rangle {dollar}型占主导的晶体学织构，该特征占22 {dollar} spcirc在该偏斜区域观察到的疲劳裂纹轮廓的偏差和FCG的晶体剪切微观机制。在WM样品的缺口尖端确定了较高的压缩残余应力，从而导致较低的FCG率。 HAZ中的FCG显示出对{dollar} Delta {dollar} K的显着依赖性，并且受HAZ靠近FL的影响。建立了焊接热循环和热影响区硬度之间的数学关系，并建立了一个概念模型，将裂纹轮廓与纹理材料中紧密堆积的平面的取向相关联。

著录项

  • 作者

    Rading, George Odera.;

  • 作者单位

    The University of Alabama.;

  • 授予单位 The University of Alabama.;
  • 学科 Engineering Metallurgy.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 1994
  • 页码 205 p.
  • 总页数 205
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;工程材料学;
  • 关键词

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