Effect of Power Ultrasonic on Solidification Structure of HT150 Gray Cast Iron

Power ultrasonic treatment is an efficient way to improve the solidification structure and mechanical properties of metals. The effect of 600 W power ultrasonic treatment on the solidification process and structure of HT150 gray cast iron has been studied, and the fining mechanism of power ultrasonic has been analyzed.

Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.

EFFECT OF ULTRASONIC POWER ON THE HEAVY ALUMINUM WEDGE BONDING STRENGTH

Eleven groups of wire bonding experiments are carried out on an experiment platform （restructured with a U3000 heavy aluminum wedge wire bonder）. Pure silicon aluminum wire （300 μm in diameter, 2.94-3.92 N in average pull force） and nickel coated aluminum substrates are used in the experiments. During the experiment process, only ultrasonic power rate parameter is changed and the other bonding parameters are kept as constant, The bonding force and time are 4.90 N and 100 ms respectively. After the bonding experiments, shear strength tests are carried out on the bonds as the bonding strength criterion. From those experiments and test results, some conclusions are obtained： In the small ultrasonic power rate conditions （about 20%-30%）, with the power increasing, the bonding strength enhances accordingly; However, in the large ultrasonic power rate conditions （about 45%-70%）, the bonding strength decreases accordingly and over bonding happens. Only when the ultrasonic power rate is in a moderate condition （about 35%-40%） can good and stabilized bonding strength be acquired.

Modification of Pb(Zr,Ti)O3 by Doping Mo based on High Power Ultrasonic Transducer

In view of the special requirements of transducers for power ultrasonic processing,the piezoelectric ceramic material Pb(Zr,Ti)O3 was modified by adding other effective elements.The piezoelectric ceramic piece has a good crystal phase structure,a stable piezoelectric constant,a higher dielectric constant,and a lower dielectric loss by adding a small amount of Sr^2+,Ba^2+,Ga^2+,Sn^4+,Nb^5+,etc.These properties are well suited to requirements of power ultrasonic transducer more than 1 000 W.The crystal phase structure and surface morphology of the modified piezoelectric ceramic chips were analyzed by X-ray and scanning electron microscopy (SEM) to prove that the piezoelectric ceramic chips have good crystal structure and density.The dielectric constant of the polarized piezoelectric ceramic chips was measured using an LCR meter.Finally,the piezoelectric ceramic chips were used to design the ultrasonic transducer,and the transducer was analyzed and measured by the impedance analyzer.The measurement results show that the performance of the piezoelectric ceramic chips is reasonable and feasible.

Microstructure Evolutions and Properties of Al-Cu Alloy Joint in the Pulsed Power Ultrasonic-Assisted GMAW

The pulsed power ultrasonic-assisted gas metal arc welding(PU-GMAW)is a new development hybrid welding method.The influences of the pulsed power ultrasonic on the microstructure evolution of the welded joint of Al-Cu alloy were investigated by using scanning electron microscopy,transmission electron microscope and electron back scattering diffraction.The results showed that the efficient heat input in the PU-GMAW was increased by above 100%compared with the traditional GMAW.The grain and eutectic of the PU-GMAW weld seam were refined compared with that of the GMAW.Cavitation and acoustic streaming induced the dendrite fragmentation(α-Al)and heterogeneous nucleation,which were the main reasons for the grain refinement.The microhardness of the PU-GMAW welded joint was improved compared with that of the GMAW owing to the change of the eutectic and grain.

Measurement of acoustic field radiated by low frequency power ultrasonic transducer with laser-interferometer

Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everywhere can be determined absolutely by laser-interferometric technique and relative distribution of pressure in the middle and far acoustic field, which can be obtained from theory or experiment respectively. Theory and experiment of measurement of pressure in acoustic field with laser-interferometer are introduced. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique. The theoretical and experimental results are in good agreement. The receiving sensitivity of a PVDF (Polyvinylidene fluoride) transducer in free field is also calibrated absolutely due to above results and its sensitivity is -118.5 dB.