Comparative analysis

Titanium and its alloys are widely used in aerospace, biomedical and chemical industries due to their high strength, low density, excellent corrosion resistance and biocompatibility. As a key forming process, hot extrusion can completely densifize the powder at high temperature, while accurately controlling the material composition and internal microstructure. In order to prevent the oxidation of activated titanium powder, the "canning" method is usually used: the powder or compact is sealed in a vacuum jacket (usually low carbon or stainless steel) before extrusion. The cladding material must have good thermoplasticity, remain non-reactive with titanium, and be easily peeled off after extrusion. Currently, three main hot extrusion processes dominate:

Process 1: Integrated forming, sintering and hot working

• Workflow:, the process integrates the three stages into one continuous stream. After initial molding, the powder is sintered by diffusion to bond the particles, and then immediately hot extruded to refine the internal structure and produce high-performance components.

• advantages:its main advantage lies in the high production efficiency through the reduction of intermediate steps. Due to the structural optimization during hot working, the resulting products exhibit excellent mechanical properties (strength and toughness).

• Disadvantages:it requires extremely tight parameter control. Minor fluctuations in pressure or temperature during forming may damage subsequent stages, resulting in defects such as cracks or voids.

process 2: hot extrusion of presintered powder compacts

• Workflow:titanium powder is pressed into a compact and then sintered to achieve a specific density and strength. For example, Ti-32Mo alloy is extruded at $1000 \ text{--}1100 ^{\ circ}\ text{C}$after sintering. This method can achieve a theoretical density of $98.6 \%\ text{--}99.1 \%$.

• advantages:it is a mature and easily controlled process. Pre-sintering improves material flow during extrusion, resulting in a uniform microstructure. The density and mechanical properties can be adjusted by adjusting the extrusion ratio.

• Disadvantages:production cycle is longer, which increases time and cost. Uneven shrinkage during sintering can also affect dimensional accuracy, sometimes requiring additional processing.

Process 3: Canned Filling and Extrusion

• Workflow:designed for complex cross-sections, this involves preparing the cladding cavity according to the final product size and extrusion ratio. Prior to extrusion, the cavity is filled with powder by vibration, evacuation and sealing. Finally, the cladding is stripped.

• advantages:Its outstanding feature is the ability to produce complex, non-standard cross-sections that cannot be achieved by other methods, while maintaining a uniform internal structure.

• Disadvantages:process is very complex and requires specialized equipment and precision. Variations in powder filling or coating size may cause defects, and the peeling process may damage the product surface, requiring post-processing.

Conclusion:

every process has its trade-offs. Manufacturers must balance efficiency, complexity, and product requirements to choose the best method, aiming to maximize quality while minimizing costs.