Development of β-type Ti-x at. % Mo alloys by mechanical alloying and powder metallurgy: Phase evolution and mechanical properties (10 ≤ x ≤ 35)

Abstract

Titanium-based alloys with fine grain structure represent a class of engineering materials that can exhibit a unique combination of properties. This paper presents the structural evolution of the β phase in Ti-x at. % Mo (x = 10, 23, 27, 31 and 35) alloys synthesized by mechanical alloying with different milling times between 15 min and 48 h and powder metallurgical process with cold powder compaction and sintering or interchangeably hot pressing. The binary alloys were characterized by X-ray diffraction, scanning electron microscopy, chemical composition determination as well as density and porosity measurements. The influence of the chemical composition and method of processing on the final microstructure, and mechanical properties of bulk alloys were studied. The mechanically alloyed Ti23Mo, Ti27Mo and Ti31Mo materials upon sintering at 800 °C for 5 min led to the formation of single β type phase alloys. All these β-type alloys have elastic modulus lower than CP microcrystalline α-Ti, but their hardness is nearly 3 times higher (approx: 460 HV0.3). The present study has demonstrated that these single phase β-type alloys with fine grain microstructure can be fabricated by the application of hot pressing of mechanically alloyed powders at the temperature below α→β transus (800 °C).