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Muhammad Iman Utama,Nokeun Park,Eung Ryul Baek 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
We studied the relationship between phase transformation and mechanical property of electron beam welded dissimilar titanium(Ti) alloy between Ti–10V–2Fe–3Al (Ti1023) and Ti–6Al–4V (Ti64). A new chemical composition in the fusion zonegenerated a moderately high beta (β) phase stability which made the precipitation of acicular alpha double-prime martensite,resulting in enhanced hardness. Fracture took place during tensile test in the heat affected zone (HAZ) of Ti1023 becausesecondary alpha (αs) phase transformed into β during welding, resulting in a loss of strength during welding. Post weld heattreatment (PWHT) successfully regained αs and improved the mechanical properties in Ti1023 HAZ, resulting in preventingfailure at Ti1023 HAZ but occurring at Ti64 base during tensile test. A development of tri-modal structure, consistingof a globular and lamellar structure of primary alpha and fine αs precipitation, in both Ti64 base and Ti64 HAZ occurredafter PWHT. The tensile property was improved after PWHT showing tensile strength with 1065 MPa and 9% elongation.
Origin of Surface Irregularities on Ti–10V–2Fe–3Al Beta Titanium Alloy
Muhammad Iman Utama,Abdul Aziz Ammar,Nokeun Park,Eung Ryul Baek 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2
We studied the origin of different characteristics and properties of a Ti–10V–2Fe–3Al beta (β) titanium alloy with surfaceheight irregularities that occurred during machining. The height differences were observed in two different regions, labeledas “soft region” and “hard region.” The present study showed a higher Fe and a lower Al content in the hard region, whichresulted in higher β-phase stability to resist primary alpha (αp) phase precipitation caused by a failure of the solution treatmentprocess. In contrast, the soft region contained a higher volume fraction of αp phase and a lower volume fraction ofthe matrix, which consisted of a combination of β and secondary alpha (αs) phase. A high number of αs/β interface in thematrix with a predicted hardness of 520 HV generated an improvement of hardness in the hard region. Therefore, the hardand the soft regions had different abilities to resist wear during machining process, resulting in surface height irregularities.