ULTRASONIC BACKSCATTERING IN DUPLEX MICROSTRUCTURES - THEORY AND APPLICATION TO TITANIUM-ALLOYS

A theory is presented for the ultrasonic backscattering in duplex micr ostructures. Assuming single scattering described by the Born approxim ation, we consider a microstructure consisting of macrograins containi ng colonies with crystallographically related orientations. General re sults are presented for the backscattering coefficient, assuming that all variants occur with equal probability. These are then applied to t he particular case of titanium alloys, in which the macrograins are ta ken to be prior beta grains and the colonies are assumed to be alpha p hase produced by a martensitic transformation. Numerical results illus trate the effects of ultrasonic frequency, colony size and ellipticity , and macrograin size and ellipticity on the backscattering.