Microstructural Variation and a Physical Mechanism Model for a Ti-55511 Alloy during Double-Stage Hot Deformation with Stepped Strain Rates in the ß Region.

The microstructural variation and high-temperature flow features of a Ti-55511 alloy in the ß region are studied by utilizing double-stage compression with a stepped strain rate. The results demonstrate that the stresses in the latter stage of hot compression markedly reduce as the strain at the previous stage or the strain rate at the previous/latter stage drops. Moreover, the annihilation/interaction of substructures is promoted, and the distinct refinement of the dynamic recrystallization (DRX) in the ß grain can be found. However, the coarsening of the ß grain and the consumption of dislocation substructures are accelerated at high temperatures. Furthermore, the principal DRX nucleation mechanism of the Ti-55511 alloy during double-stage compression with a stepped strain rate in the ß region is discontinuous DRX. Additionally, by using the microstructural variation characteristics related to the forming parameters, a physical mechanism equation is modeled to forecast the forming features, the DRX fraction, and the size of the ß grain in the investigated alloy. The forecasted results are in accordance with the tested results, indicating that the established model can accurately forecast the microstructure variation and flow features of the studied alloy.

Note: A valve-type piezoelectric reciprocating pump with secondary resonant vibrator.

A valve-type piezoelectric diaphragm pump using secondary resonant vibrator is introduced in this paper. The secondary resonant vibrator, which is mainly composed of a first vibrator and a second vibrator, is used to coordinate the frequency incompatibility between piezoelectric elements and check valves. The intermittent vibration of the first vibrator excites the resonant vibration of the second vibrator. The diaphragm in the pump chamber moves with the second vibrator, resulting in chamber volume and pressure variations. Control circuit capable of frequency tracking is designed. Vibration displacement and flow rate changing with driving voltage amplitude, frequency, and backpressure are studied in experiments. The flow rate of a prototype driven by voltage of 712 Vpp is 13.94 ml/min at secondary resonant frequency of 6 Hz.