Alloys yield strength values

Ti-16V-2.5Al is an age-hardenable alloy. A range of tensile properties is attainable, with yield strength values greater than 1240 MPa (180 ksi)... 

The following table gives a number of yield O strength valnes (in MPa) that were measured on the same almnimun alloy. Compute average and standard-deviation yield strength values. ... 

Measurements of stress relaxation on tempering indicate that, in a plain carbon steel, residual stresses are significantly lowered by heating to temperatures as low as 150°C, but that temperatures of 480°C and above are required to reduce these stresses to adequately low values. The times and temperatures required for stress reUef depend on the high temperature yield strength of the steel, because stress reUef results from the localized plastic flow that occurs when the steel is heated to a temperature where its yield strength is less than the internal stress. This phenomenon may be affected markedly by composition, and particularly by alloy additions. 

Fig. 10.10. Detailed TTT diagram for the Al-4 wt% Cu alloy. We get peak strength by ageing to give 8". The lower the ageing temperature, the longer the ageing time. Note that GP zones do not form above 1 80°C if we age above this temperature we will foil to get the peak value of yield strength.

The usefulness of this formula is restricted by the difficulty of obtaining good values to substitute in it. They must apply to the alloy selected, and be derived from carefully controlled tests on it. The stress value, S, reflects an engineer s Judgment in the selection of elastic limit or some arbitrary yield strength. The modulus value must match this. The restraint coefficent, K, is seldom known with any precision. 

If the missing data are essential and cannot be found, then there are still two possibilities. The problem can be solved in terms of the missing value by assigning a symbol to it. For example, the solution might be 37.2Y where Y is the yield strength of the alloy in MPa. The other possibility is to estimate the missing value and assume it in the calculation. In this case the assumption should be made clear to the reader. 

Through control of an ordered—disordered transformation, the yield strength of these alloys increases at elevated temperatures above the room-temperature yield strength. One composition, for example, exhibits a yield strength of 480 MPa (70,000 psi) at ca 750°C compared to its room temperature value of 345 MPa (50,000 psi). The alloys also show good resistance to radiation-induced swelling (see Fusion ENERGY). These alloys can be... 

Alloy Tensile strength, (MPa) Yield strength, (MPa) Elongation (%) in 2 in. typical minimum values Brinell hardness... 

For this analysis, symmetrical parts have been considered Figure 7 shows the contour plot of Oy stress. As expected the Ni-rich layers at the surfaces are under compression and the Copper -rich layers in the central part under tension. The peak values varies between 100 and -100 MPa. From the contour plot of the plastic deformation shown in figure 10, we can see that all of them occur in the pure metal layers in both Ni and Cu. This is explained by the low yield strength of pure Cu and Ni which are soft metals as compared to the solid solutions hardened CuNi alloys. 

Alloys within Nb system are also brittle in tension up to 1000°C. They exhibit compressive yield strengths of 1600 MPa at room temperature, 1500 MPa at 800°C and then rapid drop to 600 MPa at 1000°C and 300 MPa at 1100°C. Below the B/D transition temperature, the tensile fracture strengths exhibit considerable scatter with average values of - 250 MPa. In both systems ffactography reveals that below the B/D transition temperature, the tensile fracture is initiated by large silicides or silicide agglomerates. 

Tables V and VI show that the tear strengths were generally more than twice the yield strength, further evidence of the extremely high notch toughness of these materials and their welds. For the parent metal of both alloys, the UPE values were quite high at room temperature. For alloy 5083 at 77 K, the UPE values were about 1.5 times those at room temperature. For alloy AMg6, the low-temperature values were only slightly higher than those at room temperature.

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