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首页> 外文学位 >Evolution of Microstructure, Microtexture and Mechanical Properties in Linear Friction Welded Titanium Alloys.
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Evolution of Microstructure, Microtexture and Mechanical Properties in Linear Friction Welded Titanium Alloys.

机译：线性摩擦焊接钛合金的微观结构，微观组织和力学性能的演变。

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摘要

Two titanium alloys were welded using linear friction welding (LFW) techniques. The two alloys consisted of one alpha + beta alloy, Ti-6Al-4V, and one near-beta alloy, Ti-5553. The welding conditions were varied in order to assess the effect of each parameter on the mechanical properties, microstructure, and crystallographic texture of the materials. Axial pressures from 50 MPa to 150 MPa, oscillation frequencies from 30 Hz to 110 Hz, and oscillation amplitudes from 1.5 mm to 3 mm were employed.;The maximum strains and strain rates experienced by the material during LFW for each set of welding parameters were estimated based on the process parameters and the measured time of oscillation. A heat input equation was developed in order to estimate the temperature at different points in the joint and temperature measurements were made during welding to corroborate the calculated temperatures. The strains, strain rates and temperatures measured and calculated for the welding conditions employed were found to be sufficient to initiate dynamic recrystallization in both alloys. This finding is in agreement with the microstructures and textures observed in the weld centres.;The near-beta Ti-5553 alloy was examined not only in the as-welded state but also in two post-weld-heat-treated (PWHT) conditions. The TMAZ and weld centre of this alloy were weakened by welding due to the reduction of the alpha phase volume fraction during rapid cooling from super-transus temperatures in and near the weld. With the restoration via PWHT plus aging of the alpha phase fraction, the UTS's for the welded samples were restored to the literature values for the heat-treated condition of this alloy.;In addition to the two titanium alloys comprising the main focus of the study, a number of other materials were examined in the context of linear friction welding. These were: IMI-834, a near-alpha titanium alloy (nominally Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si); CMSX-4, a single crystal Ni-based superalloy (Ni.9.5Co-6.4Cr-6.4Ta-6.4W-5.6Al-2.9Re-1Ti-0.6 Mo-0.1Hf wt %); stainless steel 316L; mild steel A42; as well as dissimilar pairs aluminum alloy 6063 to commercial purity Cu and stainless steel 316L to Zr alloy Zr702. All of these materials were successfully linear friction welded after some refinement of the welding parameters.;The linear friction welded (LFWed) samples of Ti-6Al-4V and Ti-5553 were examined using electron backscatter diffraction techniques (EBSD) to relate the texture and phase changes to the thermomechanical conditions. Characterization of the welds included analysis of the microstructural features of the weld region and thermomechanically affected zone (TMAZ) in relation to the parent material. Mechanical properties were evaluated using tensile tests and microhardness measurements.
机译：使用线性摩擦焊接（LFW）技术焊接了两种钛合金。两种合金由一种α+β合金Ti-6Al-4V和一种近β合金Ti-5553组成。改变焊接条件以评估每个参数对材料的机械性能，微观结构和晶体织构的影响。轴向压力从50 MPa到150 MPa，振荡频率从30 Hz到110 Hz，振荡幅度从1.5 mm到3 mm .;对于每种焊接参数，材料在LFW期间经历的最大应变和应变率分别为根据工艺参数和测得的振荡时间进行估算。为了估计接头中不同点的温度，开发了一个热输入方程，并在焊接过程中进行了温度测量以证实计算出的温度。发现并针对所采用的焊接条件测量和计算出的应变，应变速率和温度足以在两种合金中引发动态再结晶。这一发现与在焊接中心观察到的显微组织和织构相吻合。不仅在焊接状态下而且还在两种焊后热处理（PWHT）条件下检查了近βTi-5553合金。这种合金的TMAZ和焊接中心由于焊接过程中的α-相体积分数的降低而被焊接所削弱，这是由于在焊缝中及其附近的超瞬时温度导致的快速冷却过程中。通过PWHT修复和α相分数的时效处理，将焊接样品的UTS恢复到该合金热处理条件下的文献值。除了两种主要研究的钛合金外，在线性摩擦焊接的背景下检查了许多其他材料。它们是：IMI-834，一种近α钛合金（名义上为Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si）； CMSX-4，一种单晶镍基高温合金（Ni.9.5Co-6.4Cr-6.4Ta-6.4W-5.6Al-2.9Re-1Ti-0.6 Mo-0.1Hf wt％）； 316L不锈钢；低碳钢A42;以及铝合金6063和商业级纯铜，316L不锈钢和Zr合金Zr702。在对焊接参数进行一些改进之后，所有这些材料都成功地进行了线性摩擦焊接。；使用电子背散射衍射技术（EBSD）检查了Ti-6Al-4V和Ti-5553的线性摩擦焊接（LFWed）样品和相变到热机械条件。焊缝的特征包括分析与母材有关的焊缝区域和热机械影响区（TMAZ）的微观结构特征。使用拉伸测试和显微硬度测量来评估机械性能。

著录项

  • 作者

    Dalgard, Elvi C.;

  • 作者单位

    McGill University (Canada).;

  • 授予单位 McGill University (Canada).;
  • 学科 Engineering Aerospace.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 153 p.
  • 总页数 153
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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