Advances in Titanium Technology: Session VI
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Yufeng Zheng, University of North Texas; Zachary Kloenne, Ohio State University; Fan Sun, Cnrs Umr 8247 - Chimie Paristech Psl; Stoichko Antonov, National Energy Technology Laboratory; Rongpei Shi, Harbin Institute of Technology (Shenzhen)

Wednesday 2:00 PM
March 22, 2023
Room: Cobalt 500
Location: Hilton

Session Chair: Qing Tan, Max-Planck-Institut für Eisenforschung GmbH


2:00 PM  Invited
On the Relationships between Twinning and Stress-induced Martensite in Superelastic Beta Titanium Alloys: Emmanuel Bertrand1; Philippe Castany2; Yang Yang3; Isabelle Braems1; Thierry Gloriant2; 1Nantes Université; 2INSA Rennes; 3Guangdong University of Technology
     β superelastic titanium alloys are subject to many deformation mechanisms that can be activated successively or simultaneously during deformation. Post-mortem observations show the presence of twins in the beta phase: most often {332}<113> and more rarely {112}<111>. These twins are most often formed under stress, when the material has undergone a reversible martensitic transformation in the α'' phase.A Schmid factor analysis of the twins shows that the {112}<111> twins in superelastic alloys are formed in the opposite direction to the twins observed in the stable centred cubic structures. The role of the martensitic transformation on the activation of this "anti-twinning" will be discussed.

2:30 PM  Cancelled
Implications for Hydride Formation in Commercially Pure Titanium and their Deformation Mechanism: Qing Tan1; Stoichko Antonov2; Zhiran Yan3; David Dye4; Baptiste Gault1; 1Max Planck Institut für Eisenforschung, GmbH; 2National Energy Technology Laboratory; 3University of Science and Technology Beijing; 4Imperial College London
    In commercially pure titanium alloys (CP-Ti), β-stabilizing elements can lead to the retention of a low volume fraction of β-phase (β-pocket), which is critical to hydrogen embrittlement. In this study, we employed cryogenic sample preparation via focused ion beam for atom probe tomography to analyze the α-α and α-β sections of the abutting grain boundary of a β-pocket. Subsequently, the deformation behavior of the formed hydrides was investigated by in-situ deformation and synchrotron x-ray diffraction. We propose that β-stabilizing impurities have an indirect effect on hydrogen embrittlement as they stabilize the β-pockets, which along with the grain boundaries are the key factors for the formation of hydrides. High internal and interphase stresses were generated within and around hydrides due to the volume expansion induced by the formation of hydrides. This work aims to bridge the atomic-scale formation and macro-scale deformation of hydrides to understand the hydrogen embrittlement of CP-Ti.

3:00 PM  
Ti Alloy Wire Fabrication from Waste and Out-of-Specification Particulates: Robert Wilson1; Geoffrey de Looze1; Kun Yang1; Shiqin Yan1; David Ritchie1; Ling Chen1; Andrew Yob1; Dayalan Gunasegaram1; 1Csiro
    Titanium is used in high technology sectors such as aerospace and defence. The manufacture of components via subtractive manufacturing (SM), additive manufacturing (AM) and during powder manufacture, has waste generation levels 10% to 81%. This particulate waste has relatively low value and is typically remelted and returned to the beginning of the titanium supply chain. Titanium wire is an important feedstock for large format wire-AM and in the production of powder for use in powder-based AM. The re-purposing these waste particulates and directly converting them into wire is a way to add value and lower the cost of wire fabrication. CSIRO has invented a process, “TiWi,” to continuously convert low-cost titanium particulates from novel and recycled sources to titanium wire. The following will describe the continuous fabrication of 3.2mm diameter Ti-64 wire from alloy particulates, the feed particulates and their reconditioning for wire making, and the resultant alloy wire

3:20 PM Break

3:40 PM  
Phase Transformation Behavior during Ultrasonic Welding of Pure Ti Sheets with Fe Interlayer: Syronn Francisco1; Kuan-Chieh Hu1; Jheyu Lin1; 1National Taipei University of Technology
    This study investigated the feasibility of joint production between commercially pure Ti sheets (Grade 2) by using ultrasonic welding (USW), a solid-state bonding process. Lap shear test evaluating joint strength and microstructural characterization using electron microscopy techniques exhibited that joints without interlayers are challenging to be ultrasonically welded. Fracture observation revealed that brittle fracture was the main feature and could be attributed to lower deformation of alpha-Ti. Comparatively, Ti sheets with a thin Fe interlayer sputtered on the bonding interface were successfully joined. This could be attributed to frictional heat and severe plastic deformation applied by static load and high-frequency oscillation during USW. And such heat-deformation interactions could facilitate Fe diffusion into the Ti matrix, leading to phase transformation from alpha-Ti (hexagonal close-packed) to beta-Ti (body-centered cubic) with improved deformability to form an integrated bonding interface.

4:00 PM  
Mechanical, Thermal Conductive and Anti-wear Properties Improvement in Titanium Matrix Composites Reinforced with Graphene Nanosheets: Qi Yan1; Biao Chen1; Wenfeng Lu2; Hao Wang2; Jinshan Li1; 1Northwestern Polytechnical University; 2National University of Singapore
    The simultaneous improvement in strength, thermal conductivity and tribol-characteristic performance has been seldom achieved in titanium matrix composites (TMCs). Herein, an effective powder metallurgy method is developed to fabricate TMCs reinforced by the high-content graphene nanosheet (GNS) with improved mechanical strength and functional performance. It is found that quasi-continuous-networked GNS not only construct a thermal channel for thermal conduct with reduced sp3 defects but also contribute to the self-lubricating performance of the composites. The results suggest that the as-fabricated 10.61 vol% GNS/Ti64 composites obtain an outstanding improved performance combination of 63.6% enhancement in compressive yield strength, 5.4% reduction in weight, 46.3% improvement in thermal conductivity, and 48.1% reduction in the coeffect of friction with 98.2% decrement for wear rate simultaneously. This study has achieved a dramatic improvement in comprehensive performance in Ti alloys and provided a simple method to develop metal matrix composites with load bearing and functional performance.

4:20 PM  
Improvement of Mechanical Properties of Pure Ti by Combined Process of Multi-directional Forging and Conventional Thermo-mechanical Processing: Hiromi Miura1; Yutaro Iwabuchi1; Masakazu Kobayashi1; Tomotsugu Shimokawa2; Chihiro Watanabe2; 1Toyohashi University of Technology; 2Kanazawa University
    Pure Ti was multi-directionally forged at room temperature employing various pass strains from 0.2 to 0.8 and forging strain rates from 1.0×10-3s-1 to 1.0×10-2s-1. In the all MDFing conditions, grains were gradually fragmented with increasing cumulative strain of MDFing. The forging stress increased more rapidly when the pass strain became larger, and the hardness also increased accordingly. Nevertheless, failure tended to take place more easily with increasing pass strain. When examined the evolved microstructure, it was found that grain fragmentation looked more proceeded with increasing pass strain and strain rate. This grain subdivision was mainly induced by multiple twinning. Tensile strength was gradually increased with cumulative strain and superior mechanical properties of tensile strength of about 1GPa and fracture strain of 20% were attained. Tensile strength was more raised by ageing and cold rolling up to 1.2 GPa with ductility of about 10%.