John Wanagel

Pressure transition of AlP to a conductive phase

Van Vechten, using a semi‐empirical theoretical approach, has computed the equilibrium pressures at which various III‐V compounds as well as C, Si, Ge, Sn, and SiC transform to the metallic β‐tin phase. A characteristic of each of the groups BX, AlX, GaX, and InX, where X is a specific metalloid (N, P, As, Sb), is that the theoretical transformation pressure decreases as the atomic number of the metal atom B, Al, Ga, and In increases. The calculated values for the sequence BP, AlP, GaP, and InP are 401, 269, 216, and 141 kbar, respectively. Currently published values are available for GaP at 220 and 240 kbar and for InP at 105–115 kbar. In the present experiment, in which a direct simultaneous electric resistance comparison method is used, it is shown that AlP becomes conductive at a pressure equal to or less than ZnS which has been shown to transform at 150 kbar. Note should be made of the fact that the pressure at which we find AlP to be conductive is clearly considerably less (rather than more) than th...

Evaluation of Mechanical Properties of Thin Wires for Electrical Interconnections

A miniaturized universal testing machine was used to measure the yield stress, elastic and anelastic modulus, load relaxation, and low cycle fatigue properties of bonding wires. These material properties were found to be sensitive to the mierostructure of the material produced by a variety of thermal and mechanical treatments. The relations established between structure and properties can potentially be used as a basis for optimizing the bonding wire perform- ance.

Crystallographic Study of the Low‐Temperature Phase Transformation in V3Si and Nb3Sn

The cubic‐tetragonal phase transformation in V3Si and Nb3Sn has been investigated dynamically with optical and x‐ray techniques. For Nb3Sn a simple shear on the {110} 〈110〉 completely describes the lamellar morphology in the tetragonal state. The lamellar structure and associated shear are concluded to arise from an accommodation of internal stresses and are a result of, not a mechanism for, the transformation. All our observations are consistent with a continuous transformation from the cubic to tetragonal state with no evidence of hysteresis or the coexistence of the two phases.

Yield stress of cemented tungsten carbide

Cemented tungsten carbide yields plastically at room temperature in the presence of a large hydrostatic pressure component. By approximate analysis of the state of stress in supported opposed anvils and by measurement of the pressure at which the anvil tips exhibit a permanent deviation from planarity, we have obtained the yield stress of such materials. Our value for the yield stress of a 3% cobalt cemented tungsten carbide is 86 kbar.

High pressures with supported opposed steel anvils

It is shown that opposed, supported maraging steel anvils are capable of generating pressures in excess of the upper bismuth transition at 75 kilobar, and in excess of the InAs transition at 85 kilobar, or more than four times the compressive yield stress of the material.