Key Takeaways & Executive Findings
- •• A novel strategy combining thermal debinding temperature regulation and LaB6 addition effectively mitigates oxygen contamination in MIM Ti6Al4V, achieving a superior strength-ductility synergy. • The fabricated MIM Ti6Al4V exhibits excellent mechanical properties: UTS of 967 MPa, yield strength of 866 MPa, and elongation of 21.4%, among the best reported for MIM Ti6Al4V. • The underlying mechanisms include accelerated dislocation slip due to reduced dissolved oxygen, grain refinement, and in situ formation of TiB whiskers and La2O3 particles. • This work provides a practical pathway for producing high-performance MIM titanium alloys, with potential for industrial scale-up and application in aerospace and biomedical fields.
Abstract
Interstitial oxygen (O) contamination remains a substantial challenge for metal injection molding (MIM) of titanium alloys. Herein, this critical problem is successfully addressed by regulating the thermal debinding temperature and incorporating the oxygen scavenger LaB6. Results indicate that the surface oxide layer (with a thickness of (13.4 ± 0.5) nm) of Ti6Al4V powder begins to dissolve into the Ti matrix within the temperature range of 663–775°C. O contamination in MIM Ti alloys can be effectively mitigated by lowering the thermal debinding temperature and adding LaB6 powder. As a result of reduced dissolved O content, the slips of mixed and
1. Introduction
Titanium (Ti) and its alloys are widely regarded as ideal metallic materials for applications in aerospace, military, marine, and biomedical industries due to their high strength-to-density ratio, exceptional corrosion resistance, and biocompatibility [1–5]. However, the use of Ti is limited by its low material utilization efficiency and high production cost. Typically, the buy-to-fly ratio for Ti components fabricated through the machining of rolled plates or rods exceeds 20:1 [6], indicating that approximately 95% of raw materials are wasted. Several powder metallurgy (PM) techniques, particularly additive manufacturing (AM) and metal injection molding (MIM), have been rapidly developed in recent years to address this issue. AM and MIM technologies both offer the capability to manufacture complex Ti parts with high material utilization rates and design flexibility. Compared to AM, MIM possesses superior production efficiency, making it especially suitable for the mass production of small-sized complex Ti parts [7–8].
However, interstitial O contamination remains a considerable challenge for MIM Ti alloys. O and Ti exhibit a strong chemical affinity, with a maximum solubility of ~14wt% in hexagonal α-Ti. The critical O content in PM Ti6Al4V alloy is reported to be ~0.33wt%; exceeding this limit reduces tensile ductility to ~5% [9–10]. Preventing O contamination during MIM is more challenging than those of other PM technologies for two main reasons: (1) fine Ti powder (<40 µm) is ideal for acquiring relatively high density and dimensional accuracy [11], but its large specific surface area increases susceptibility to O adsorption; (2) most MIM processes are performed at high temperatures, which can lead to an additional O uptake of ~0.1wt% [12–13]. Therefore, finding ways to mitigate the oxygen-induced brittleness in MIM Ti alloys is crucial.
In the initial Ti powder, O mainly exists as surface oxide layers and interstitial atoms within Ti lattices [14]. Using some rare earth (RE) elements or compounds that have a higher affinity for O than Ti can effectively scavenge O from these oxide layers [15]. Recent studies have shown that adding RE elements can reduce the dissolved O content in MIM Ti alloys and improve mechanical properties. For example, Limberg et al. [16] investigated the effect of yttrium addition on the mechanical properties of MIM Ti6Al4V alloy. They found that incorporating 0.5wt% yttrium powder resulted in excellent mechanical properties, achieving an ultimate tensile strength (UTS) of 939 MPa and an elongation (EL) of 13.5%. Given the high cost and poor oxidation resistance of pure RE powders, Liu et al. [17] opted for the inexpensive and chemically stable lanthanum boride (LaB6) as an O scavenger. This approach enhanced the EL of pure Ti from 5.7% to 15% while maintaining a high UTS of 632 MPa. Other RE-based compounds, including YH2 [18], LaH2 [19], NdB6 [20], and CeSi2 [21], have the potential to be effective O scavengers for MIM Ti alloys. However, the additive con...
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Jianzhuo Sun, Yu Pan, Yanjun Liu, Fan Kuang, Ranpeng Lu, Xin Lu (2025). Strength–ductility synergy strategy of Ti6Al4V alloy fabricated by metal injection molding. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-3023-4
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Frequently Asked Questions
What is the main challenge addressed in this study?
The main challenge is interstitial oxygen contamination in metal injection molding (MIM) of titanium alloys, which causes brittleness and reduced ductility.
How do the authors mitigate oxygen contamination?
They regulate the thermal debinding temperature and incorporate the oxygen scavenger LaB6, which effectively reduces dissolved oxygen content in the Ti matrix.
What are the key mechanical properties achieved?
The fabricated MIM Ti6Al4V sample achieves an ultimate tensile strength of 967 MPa, a yield strength of 866 MPa, and an elongation of 21.4%, representing some of the best results reported for MIM Ti6Al4V.
What mechanisms contribute to the improved strength and ductility?
The improved ductility is attributed to accelerated dislocation slip due to reduced dissolved oxygen, while strength enhancement comes from grain refinement and in situ formation of TiB whiskers and La2O3 particles.
What is the significance of this study?
This study provides a practical strategy for producing high-performance MIM titanium alloys, offering insights for industrial applications in aerospace, biomedical, and other fields.
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