Effects of Thermo-Mechanical Processing on the Microstructure and Mechanical Properties of β -Type Titanium Alloys

Year 2024, Volume: 36 Issue: 1, 50 - 58, 25.03.2024

Hakan Yılmazer , Muhammed Enes İlgazi

https://doi.org/10.7240/jeps.1412097

Abstract

This study investigates the microstructural evolution and mechanical behavior of severe cold-rolled β-type Ti-29Nb-13Ta-4.6Zr (TNTZ) alloys under systematic solution heat treatments (ST) at 1063 K for durations ranging from 5 to 60 minutes. This comprehensive analysis provides valuable insights into the microstructural and mechanical characteristics of TNTZ alloys under varying solution heat treatment durations, offering a foundational understanding for optimizing their application in engineering contexts. Microstructural analysis reveals that both solution-treated (ST) and cold-rolled (CR) samples exhibit a predominant single body-centered cubic (BCC) β phase, while cold-rolled and solution-treated (CST-Q) samples display a combination of β and martensite orthorhombic α'' phases. ST samples demonstrate equiaxed grains with an average diameter of ~72 μm, albeit with limited clarity. In contrast, CST-Q samples treated for over 10 minutes exhibit finer equiaxed grains within the 7-14 μm range. Hardness values increase with prolonged solution heat treatment, reaching approximately ~183 HV for ST and ~234 HV for CR. Moreover, hardness continues to rise with increasing treatment duration, reaching ~204 HV for CST10Q, ~229 HV for CST30Q, and ~242 HV for CST60Q. Mechanical properties, including tensile strength, yield strength, and elongation, vary across samples. ST shows values of ~710 MPa, ~610 MPa, and ~25%, CR with ~1305 MPa, ~395 MPa, and ~17.5%, CST5Q with ~1042 MPa, ~440 MPa, and 17.5%, CST10Q with ~1010 MPa, ~650 MPa, and 21%, and CST60Q with ~930 MPa, ~660 MPa, and ~21%. Fracture surfaces of all samples exhibit dimple structures and microvoid nucleation, indicative of ductile failure.

Keywords

Titanium alloys, Thermomechanical processing, Heat treatments, Mechanical properties

Termo-Mekanik İşlemlerin β-Tip Titanyum Alaşımlarının Mikroyapısı ve Mekanik Özellikleri Üzerindeki Etkileri

Abstract

Bu çalışma, sistemli çözelti ısıl işlemlere (ST) tabi tutulan şiddetli soğuk haddeleme β-tipi Ti-29Nb-13Ta-4.6Zr (TNTZ) alaşımlarının mikroyapısal evrimini ve mekanik davranışını incelemektedir. 1063 K'deki 5 ila 60 dakika süren çeşitli sürelerde gerçekleştirilen bu kapsamlı analiz, TNTZ alaşımlarının mikroyapısal ve mekanik özellikleri hakkında değerli bilgiler sunmakta olup, mühendislik bağlamında uygulamalarını optimize etmek için temel bir anlayış sağlamaktadır. Mikroyapısal analiz, çözelti işlemli (ST) ve soğuk haddeleme (CR) örneklerinin çoğunlukla tek bir vücut merkezli kübik (BCC) β fazını içerdiğini ortaya koymaktadır, ancak soğuk haddeleme ve çözelti işlemli (CST-Q) örneklerinin β ve martenzit ortorombik α'' fazlarının bir kombinasyonunu sergilediğini göstermektedir. ST örnekleri 72 μm çapında eş eksenli taneler gösterirken, bu taneler sınırlı netlikte bulunmaktadır. Buna karşılık, 10 dakikadan fazla süreyle işlenen CST-Q örnekleri 7-14 μm aralığındaki daha ince eş eksenli taneleri sergilemektedir. Sertlik değerleri, çözelti ısıl işleminin uzamasıyla artmakta olup, ST için yaklaşık ~183 HV ve CR için ~234 HV'ye ulaşmaktadır. Ayrıca, sertlik, işlem süresinin artmasıyla birlikte devam ederek CST10Q için ~204 HV, CST30Q için ~229 HV ve CST60Q için ~242 HV'ye ulaşmaktadır. Mekanik özellikler, çekme dayanımı, akma dayanımı ve uzama gibi özellikler açısından örnekler arasında değişmektedir. ST, ~710 MPa, ~610 MPa ve %25, CR, sırasıyla ~1305 MPa, ~395 MPa ve %17.5, CST5Q, ~1042 MPa, ~440 MPa ve %17.5, CST10Q, ~1010 MPa, ~650 MPa ve %21 ve CST60Q, ~930 MPa, ~660 MPa ve %21 değerlerine sahiptir. Tüm örneklerin kırılma yüzeyleri, dövme başarısızlığını gösteren dimple yapıları ve mikro boşlukların nükleasyonunu sergilemektedir.

Keywords

Titanyum alaşımları, Termomekanik işleme, Isıl işlemler, Mikroyapı

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