Abstract
The effect of heat treatment on microstructure and tensile properties as well as wear behavior on TC21 (Ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-Si, wt.%) Ti-alloy was investigated. The samples were solution treated at 900°C for 15 min followed by furnace cooling to 800°C with a cooling rate 1°C/min and holding for 20 min, then the samples cooled down to room temperature either using water quenching (WQ) or air cooling (AC). Consequently, aging treatment was applied at 575°C for 4 hr. The microstructure feature showed a secondary α phase (αs) precipitated in residual β phase due to the step cooling from 900°C to 800°C inside furnace as well as the aging treatment. The highest wear rate was obtained for WQ samples due to increasing in volume fraction of αp (58%). However, the lowest wear rate was reported for WQ + Aging samples due to the high hardness. Optimum mechanical properties of the studied TC21 Ti-alloy were obtained for AC + Aging condition. A better combination of hardness, tensile properties, and wear resistance was achieved for AC + Aging samples, although their wear resistance was found to be slightly lower than that of WQ + Aging samples.
Highlights
Titanium alloys, especially α + β titanium alloys, are widely used in advanced aerospace applications, aero-engines and chemical industries
From the experimental results related to microstructure, hardness, tensile properties and wear characteristics of TC21 alloy subjected to different heat treatment processes, the following conclusions can be drawn: Figure 17
1) Duplex stage solution treatment with two different cooling rates and aging treatment, produced a structure consisted of secondary α phase precipitated in a residual β phase due slow cooling rate from 900 ̊C to 800 ̊C inside furnace or the final slow cooling rate by air as well as the aging treatment
Summary
Especially α + β titanium alloys, are widely used in advanced aerospace applications, aero-engines and chemical industries. TC21 (Ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-Si, wt.%) alloy is a new category of (α + β) titanium alloys with high strength, toughness, and damage-tolerance properties It belongs to eight-component system, which develops for structural application in advanced aircraft and aerospace [8]. By applying a heat treatment technique, TC21 alloy can obtain a better combination of tensile properties, fracture toughness, and low fatigue crack growth rate. In such case, the performance and engineering application value will be better than the widely used conventional Ti6Al4V alloy [10]. In the present study, the effect of applying duplex stage heat treatment with different cooling rates on microstructure, tensile properties as well as wear properties of TC21 Ti-alloy has been investigated
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