Advancement in the pressureless sintering of CP titanium using high-frequency induction heating

High-frequency induction heating is applied as an alternative heating source for pressureless sintering of commercially pure Ti powders, aiming to intensify the sintering process. The effects of the process parameters on the properties of the sintered material are systematically studied. The initial powder compact density is the most influential parameter permitting sintered structures with highly porous to almost fully dense appearance. Short heating time combined with sintering to temperatures just above the β-transus resulted in a strong diffusion bonding between the Ti powder particles, and grain growth is observed at the former boundaries of the neighboring powder particles. The dimpled appearance of the fracture surface at those regions confirmed the strong metallic interparticle bonding. Tensile properties comparable to those of Ti-Grade 3 and Ti-Grade 4 are achieved, which also demonstrates the efficiency of the induction sintering process. A mechanism explaining the fast and efficient sintering is proposed. The process has the added advantage of minimizing the oxygen pickup

Strong and Ductile Ti-6Al-4V Alloy Produced by Hot Pressing of Ti-6Al-4V Swarf

Ti-6Al-4V (Ti-64) swarf is produced every day in commercial operations but its direct use for the fabrication of strong and ductile Ti-6Al-4V alloy is seldom reported. This study consolidated as-received Ti-64 swarf into near fully dense Ti-6Al-4V alloy by hot pressing. The microstructures and tensile mechanical properties of the hot-pressed Ti-64 alloy and the effect of subsequent solution treatment and ageing (STA) were studied. The hot-pressed Ti-64 achieved tensile yield strength (TYS) of 928998 MPa, ultimate tensile strength (UTS) of 10761139 MPa and strain to fracture of 6.927.80%. The STA increased the TYS to 11031143 MPa and UTS to 11881223 MPa, accompanied by a decline in the strain to fracture to 5.326.48%. These tensile property data suggest that it is possible to directly consolidate Ti-6Al-4V swarf into a strong and ductile Ti-6Al-4V alloy by hot pressing for a variety of potential applications

Investigation of a discus-milling process using a powder mixture of Al and TiO₂

In this study, a powder mixture of Al and TiO₂ was employed to investigate the milling process in a discus mill. In this first report on this novel mechanical mill, several variables, including the milling time and powder charge and their effects on the microstructural evolution of powder particles, are monitored and studied. The study reveals that the dominant parameters of the milling process are the milling time and the starting powder charge, similar to the other high-energy ball-milling processes. The longer the milling time and the smaller the starting powder charge, the more homogeneous the mixing and the finer the microstructure of the powder particles. The reaction between Al and TiO₂ was not observed with a milling period as long as 6 hours, for the present materials. However, the reaction between Al and TiO₂, during the subsequent heat treatment, is influenced by the milling condition. The powders with the longer milling times and finer mixing microstructures also form a finer microstructure, after the reaction between Al and TiO₂ during heat treatment. The methods for achieving an optimal milling efficiency for the Al- TiO₂ system are discussed