EBSD characterization of cryogenically rolled type 321 austenitic stainless steel

Electron backscatter diffraction was applied to investigate microstructure evolution during cryogenic rolling of type 321 metastable austenitic stainless steel. As expected, rolling promoted deformation-induced martensitic transformation which developed preferentially in deformation bands. Because a large fraction of the imposed strain was accommodated by deformation banding, grain refinement in the parent austenite phase was minimal. The martensitic transformation was found to follow a general orientation relationship, {111}γ||{0001}ε||{110}α′ and 〈110〉γ||〈11-20〉ε||〈111〉α′, and was characterized by noticeable variant selection

Martensite-to-austenite reversion and recrystallization in cryogenically-rolled type 321 metastable austenitic steel

The annealing behavior of cryogenically-rolled type 321 metastable austenitic steel was established. Cryogenic deformation gave rise to martensitic transformation which developed preferentially within deformation bands. Subsequent annealing in the range of 600 C to 700 C resulted in reversion of the strain-induced martensite to austenite. At 800 C, the reversion was followed by static recrystallization. At relatively-low temperatures, the reversion was characterized by a very strong variant selection, which led to the restoration of the crystallographic orientation of the coarse parent austenite grains. An increase in the annealing temperature relaxed the variant-selection tendency and provided subsequent recrystallization thus leading to significant grain refinement. Nevertheless, a significant portion of the original coarse grains was found to be untransformed and therefore the fine-grain structure was fairly heterogeneous

Performance of a self-excited induction generator with DSTATCOM-DTC drive-based voltage and frequency controller

This paper presents the performance of a self-excited induction generator (SEIG) with a voltage and frequency controller (VFC) in a standalone microhydro power generating system. The VFC consists of a distribution static compensator (DSTATCOM) and a direct torque controlled variable frequency induction motor drive (VFIMD) operating as an electronic load controller (ELC). The DSTATCOM is an insulated-gate bipolar transistor-based three-leg voltage source inverter with a self-sustaining dc bus. The main objective of DSTATCOM is to regulate the system voltage through reactive power compensation. In addition to voltage regulation, the DSTATCOM compensates the harmonics generated by nonlinear loads as well as ELC. The ELC controls the system frequency through the active power balance. The VFIMD of the ELC drives a pump and it consumes the power in excess of consumer load power to maintain constant power generation at the SEIG terminals, which in turn regulates the system frequency. A prototype-proposed VFC is developed and tested with a variety of loads. Experimental results demonstrate that the proposed VFC can effectively control the system voltage and frequency