Microstructure and Properties

Because diffusion rates are higher in the beta-phase, body-cubic centered (bcc) region, sintering is generally completed at >880 °C (1620 °F). The microstructure following slow cooling is a transformed beta microstructure, which is considered an inferior structure for conventional wrought material. In the case of commercially pure titanium parts, this limitation is not significant, because static strength and corrosion resistance are of prime importance. Only fatigue and fracture toughness-related properties are affected by this microstructure.

Static properties of pressed-and-sintered P/M titanium are comparable to those of wrought material, as shown in Table 21. Fatigue resistance is not quite as good as for wrought alloys, primarily due to the presence of salt-related residual porosity and to a lesser extent the transformed beta microstructure. More current information of P/M titanium alloys is in the article "Titanium Powder Metallurgy Alloys" in this Volume.

Table 21 Comparative properties of P/M and wrought titanium

Property

Commercially pure

Ti-6Al-4V

P/M

Wrought grade II

Cold pressed, sintered blend

Wrought

Density, %

95.5

1DD

94 99

1DD

Modulus of elasticity, GPa (106 psi)

1D3 (15)

1D2.7 (14.9)

103 (15) 110 (16)

11D (16)

Reduction in area, %

14

35

3 23

43

Ultimate tensile strength, MPa (ksi)

414 (6D)

345 (5D)

754.3 (109.4) 960.5 (139.3)

948 (137)

Yield strength, MPa (ksi)

324 (47)

345 (5D)

643.3 (93.3) 884.6 (138.3)

869 (126)

Elongation, %

15

5

3 12

19

0 0

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