The Effect of Annealing, Overheating, and a Sintered Porous Coating Thermal Treatments on the Fatigue Properties of Ti-6.0wt.%Al-4.0wt.%V ELI Alloy Plate Specimens

Recent Advances in Solids and Structures Pub Date : 1998-11-15 DOI:10.1115/imece1998-0906

J. Fragomeni

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Abstract

The primary objective of this investigation was to determine the effect on the mechanical and fatigue properties induced by sintering powder on Ti-6wt.%Al-4wt.%V ELI (Extra Low Interstitial) alloy substrates as compared to annealing, and overheating thermal treatments. Fatigue tests were conducted using a variable speed plate fatigue machine on various specimens in the different thermally-treated conditions so that a comparison study of the fatigue characteristics could be performed. The heat treatments, which included as-annealed, as-overheated, and sintered porous-coated, were performed on the plate fatigue specimens prior to testing in the variable speed fatigue plate machine. A comparison study of the fatigue results/properties of the samples subjected to the three thermal treatments revealed that the annealed specimens exhibited superior fatigue resistance as compared to the as-overheated and porous-coated samples. However, a substantial decrease in the fatigue resistance of the porous coated sintered to the as-overheated thermal treatment was not evidenced. It was determined that the decrease in the fatigue resistance of the as-overheated, as compared to the annealed heat treatment, was a result of an increase in the macroscopic grain size. Furthermore, for the porous-coated specimens, it was determined that the presence of stress concentrations at the surface irregularities of the sintered bond sites resulted in the decrease fatigue resistance. It was found, from optical metallography on the sintered porous-coated samples, that microscopic fatigue cracks originated at the necked regions of both the particle-substrate interface and the particle-particle interface. From these findings it was determined that the fatigue cracks at the particle-substrate interface contributed to the ultimate fatigue failure of the sintered porous-coated plate fatigue specimens.

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退火、过热和烧结多孔涂层热处理对Ti-6.0wt.%Al-4.0wt疲劳性能的影响%V ELI合金板试样

本研究的主要目的是确定烧结粉末对Ti-6wt.%Al-4wt合金力学性能和疲劳性能的影响。与退火和过热热处理相比，%V ELI(特低间隙)合金衬底。利用变速板疲劳试验机对不同热处理条件下的不同试样进行疲劳试验，对其疲劳特性进行对比研究。在变速疲劳试验机上对疲劳试样进行热处理，包括退火、过热和烧结多孔涂层。对三种热处理试样的疲劳性能进行了对比研究，结果表明，与过热和多孔涂层试样相比，退火试样具有更好的抗疲劳性能。然而，多孔涂层烧结材料在过热热处理条件下的抗疲劳性能并没有明显下降。结果表明，与退火热处理相比，过热后合金的抗疲劳性能下降是由于宏观晶粒尺寸增大所致。此外，对于多孔涂层试样，确定在烧结键合部位的表面不规则处存在应力集中导致疲劳抗力降低。通过对烧结多孔涂层试样的光学金相分析发现，微观疲劳裂纹起源于颗粒-基体界面和颗粒-颗粒界面的颈部区域。结果表明，颗粒-基体界面处的疲劳裂纹是导致烧结多孔涂层板疲劳试样最终失效的主要原因。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Recent Advances in Solids and Structures

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