Mechanical Properties and Microstructural Evolution of TiNi-Based Intermetallic Alloy with Nb Addition

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Titanium-Nickel (TiNi) intermetallic alloys are crucial in various engineering applications.
• Understanding the influence of alloying elements on TiNi properties is essential for material design.
• Niobium (Nb) is a potential alloying element for modifying TiNi characteristics.

Purpose of the Study:

• To investigate the effect of niobium (Nb) addition on the mechanical properties and microstructure of TiNi intermetallic alloys.
• To analyze the behavior of these alloys under both static and dynamic loading conditions.
• To determine the optimal Nb content for improved TiNi alloy performance.

Main Methods:

• Preparation of TiNi alloys with varying Nb concentrations (2, 4, and 6 at.%).
• Mechanical property testing under static (10⁻³–10⁻¹ s⁻¹) and dynamic (4x10³–6x10³ s⁻¹) strain rates.
• Microstructural analysis using X-ray diffraction (XRD) and scanning electron microscopy (SEM).
• Fracture surface examination via optical microscopy (OM).

Main Results:

• TiNi alloy strength increased with Nb addition up to 4 at.%, but decreased significantly at 6 at.%.
• Plastic flow stress and strain rate sensitivity increased with strain rate for all Nb additions.
• Microscopy revealed dendritic and eutectic structures, with fracture mode transitioning from brittle to ductile as Nb content increased.

Conclusions:

• Nb addition up to 4 at.% is beneficial for enhancing TiNi alloy strength.
• The strain rate significantly influences the plastic flow stress and strain rate sensitivity of Nb-modified TiNi alloys.
• Increased Nb content promotes a transition to a more desirable ductile fracture behavior in TiNi alloys.