Mechanical properties of powder titanium at different production stages. I. Densification curves for titanium powder billets

Abstract

The mechanical behavior of titanium powder billets at all production stages is examined. The dependence of how mechanical properties are formed on the structure is established. The compaction of a powder pressed in a rigid die mold, which is the initial stage of the production process, is analyzed. The experimental dependence of the compacting force on porosity is examined. The results are compared with theoretical data available.

Analysis of the Cold Compaction Behavior of Titanium Powders: A Comprehensive Inter-model Comparison Study of Compaction Equations

“…[27] Eventually, according to Bockstiegel, [28] the interest shifted more towards an analytical problem-finding a simple but adequate mathematical description for experimentally observed compaction curves. [1,2,[6][7][8][9][10][11][12][13][14] The compaction curves for ITP-produced Ti, [12] CSIR-produced Ti, [8] Ho¨gana¨s AB produced Ti and TiH 2 , [13,17] Armstrong produced Ti and Ti-6Al-4V, [14,17] spray-dried powders, [20] for example, have also been reported Comparing the compressibility of different powder CP-Ti, sponge, HDH, and various Ti-6Al-4V powder mixtures (up to 1200 MPa) several researchers, see Refs. 1, 2, 6 through 9, 11 through 13, and 17 for example, have also studied and compared the compaction behavior of different Ti powder.…”

“…[4,5] Several studies in literature have established relationships between the compaction pressure, the powder characteristics (such as impurity levels and particle size shape), different compaction route (cold, hot, or dynamic compaction), and the obtained properties of the compacts (density, sinterability and strength) with varying degrees of success. [1,2,[6][7][8][9][10][11][12][13][14][15][16][17][18] Studies into the cold compaction of titanium and titanium-based powder materials are necessitated by fact that titanium PM also offers improved chemical homogeneity and refined microstructures [2] in addition to a cost and energy-consumption reduction benefit-given the high cost of titanium powder material. In addition, challenges associated with titanium powder compaction such as (i) the obvious high reactivity of titanium powder material in air, (ii) its inherent difficulty to press into green bodies due to its high hardness and inductile properties, [13] (iii) problems associated with compact cold welding to the die wall [9,11,13,14,19] as well as (iv) the high ejection force required.…”

“…Some noteworthy findings from literature are summarized in Table I. According to Table I, many research articles have reported on the compressibility behavior of titanium powders [1,2,[6][7][8][9][10][11][12][13][14]17,20,22,25] ; evidently, only a very few have paid particular attention to the analysis of the cold compaction behavior of titanium powders using existing or new compaction equations, see References 10,12,14,22, and 25 for example. Those that have, for unspecified reasons, have selectively applied only a few models.…”

Mechanical properties of powder titanium at different production stages. II. Mechanical behavior of porous titanium compacts

“…Figure 4 shows results from the bending tests of The elastic and strength properties of samples compacted by the same force somewhat decrease with the particle size. In our opinion, it is an apparent effect since, according to [6], the compact porosity increases with the particle size under set compaction force. The introduction of this correction using Table 1 presented in [6] somewhat decreases but does not eliminate this effect completely since the density varies along the compact height and the maximum stress is concentrated in the near-surface layers of the sample in the bending tests.…”

“…In our opinion, it is an apparent effect since, according to [6], the compact porosity increases with the particle size under set compaction force. The introduction of this correction using Table 1 presented in [6] somewhat decreases but does not eliminate this effect completely since the density varies along the compact height and the maximum stress is concentrated in the near-surface layers of the sample in the bending tests. The opposite tendency is revealed in analyzing how the porosity influences the plastic properties of sintered and green materials: the ultimate strain of sintered materials varies tenfold [5] when porosity changes from 5 to 40%, while that of green compacts changes by no more than 30% (Fig.…”