Evolution of the Microstructure and Mechanical Properties of a Ti35Nb2Sn Alloy Post-Processed by Hot Isostatic Pressing for Biomedical Applications

Abstract

The HIP post-processing step is required for developing next generation of advanced powder metallurgy titanium alloys for orthopedic and dental applications. The influence of the hot isostatic pressing (HIP) post-processing step on structural and phase changes, porosity healing, and mechanical strength in a powder metallurgy Ti35Nb2Sn alloy was studied. Powders were pressed at room temperature at 750 MPa, and then sintered at 1350 °C in a vacuum for 3 h. The standard HIP process at 1200 °C and 150 MPa for 3 h was performed to study its effect on a Ti35Nb2Sn powder metallurgy alloy. The influence of the HIP process and cold rate on the density, microstructure, quantity of interstitial elements, mechanical strength, and Young’s modulus was investigated. HIP post-processing for 2 h at 1200 °C and 150 MPa led to greater porosity reduction and a marked retention of the β phase at room temperature. The slow cooling rate during the HIP process affected phase stability, with a large amount of α”-phase precipitate, which decreased the titanium alloy’s yield strength.

Titanium Alloys and Titanium-Based Matrix Composites

“…The next four papers are devoted to titanium-based alloys and composites produced by powder metallurgy. The influence of the hot isostatic pressing (HIP) post-processing step on the microstructure, porosity and mechanical properties of Ti-35Nb-2Sn alloy was studied by Lario et al [11]. They confirmed that field-assisted consolidation processes, such as HIP, can be employed to reduce residual porosity and to increase the chemical and phase homogeneity of sintered β titanium alloys intended for biomedical applications.…”

Biomedical Applications of Titanium Alloys: A Comprehensive Review

“…The sintered material usually has good mechanical properties, also due to the controlled microstructure (the microstructure also depends on the powder quality), but often has some residual porosity. In this case, a post-treatment process is required to better consolidate the material using Hot Isostatic Pressing (HIP) [ 164 , 165 ]. The sintered component is usually impregnated at high temperature and pressure using inert gases to mechanically close the residual porosity.…”

Desarrollo de aleaciones de titanio: implicaciones en el sector biomédico europeo

“…Estas elevadas velocidades de enfriamiento (4000ᵒC/min) permiten combinar el ciclo de HIP con tratamientos térmicos convencionales donde elevadas velocidades de enfriamiento se necesitan para generar una microestructura con determinadas propiedades mecánicas (Fan et al, 2016). En el estudio realizado por Lario et al (2021) se observó la influencia que tiene el postprocesado isostático en caliente en las aleaciones Ti-35Nb-2Sn (fig. 67).…”