Ultrasonic and impact techniques used to characterize liquid-phase-sintered tungsten alloys

The Oak Ridge Y-12 Plant has been involved in producing liquid-phase-sintered tungsten alloys for penetrator applications. The majority of the effort has been centered on two materials--a 90 W-7 Ni-3 Fe alloy with 25 percent cold work and a 95 W-3.5 Ni-1.5 Fe alloy with 18 percent cold work. Fracture toughness concepts, along with instrumented Charpy impact tests, were used to measure toughness differences and temperature effects on toughness for several alloys. The instrumented Charpy was useful in screening alloys having different processing parameters. Ultrasonic techniques can be used to detect conditions of matrix depletion and incomplete sintering. Spectral analysis shows high attenuation of all frequencies in areas of matrix depletion and very low attenuation of energy between 10 and 15 MHz for conditions of incomplete sintering when compared to normal material. Efforts are underway to develop a higher density alloy. Of major concern in the higher tungsten alloys is cracking which may occur during swaging. Preliminary ultrasonic techniques to detect cracks are discussed