In the present work, the influence of step annealing heat treatment on the microstructure and pitting corrosion resistance of super duplex stainless steel UNS S32760 welds have been investigated. The pitting corrosion resistance in chloride solution was evaluated by potentiostatic measurements. The results showed that step annealing treatments in the temperature ranging from 550 to 1000°C resulted in a precipitation of sigma phase and Cr 2 N along the ferrite/austenite and ferrite/ferrite boundaries. At this temperature range, the metastable pits mainly nucleated around the precipitates formed in the grain boundary and ferrite phase. Above 1050°C, the microstructure contains only austenite and ferrite phases. At this condition, the critical pitting temperature of samples successfully arrived to the highest value obtained in this study.
This work deals with the improvement of ultimate tensile strength (UTS) of super duplex stainless steel (SDSS, UNS S32760) welds fabricated by pulsed current gas tungsten arc welding (PCGTAW) process. The Taguchi method, a design of experiment technique, was employed to optimize PCGTAW process parameters to improve the UTS of SDSS weldments. The optimum conditions were found to be the second level of pulse current (120 A), second level of background current (60 A), first level of % on time (40) and second level of pulse frequency (3 Hz). Under these conditions, UTS was predicted as 776 MPa that was very close to the observed value of 769 MPa. Analysis of variance (ANOVA) was performed on the measured data and signal-to-noise ratios. As a result of ANOVA, the % on time was found to be the most significant factor affecting the UTS of SDSS welds by percentage contribution of 62.23. The pulse current (21.13%) and the background current (16.18%) had also the next most significant effects on the UTS. The pulse frequency with the 0.46% contribution was insignificant.
Although many new materials are developed in laboratories, most of them do not get commercialized. The ranking of applications gives material engineers a better understanding of the advantages and disadvantages of any new or improved material under development. This is possible through simultaneously considering different technical, economic, and environmental criteria. It also helps to guide future research on developing new materials and identify the requirements that any new material must fulfill for the most fitting applications. The appropriateness of the proposed approach for evaluating promising applications of a new material is demonstrated using a case study in nanostructured Al/Al2O3 metal matrix composite produced via the accumulative roll bonding process. Al/Al2O3 metal matrix composite provides superior mechanical and physical properties and accumulative roll bonding is a severe plastic deformation process that can be applied to the continuous production of bulky sheet materials. The material is in growing use and becoming indispensable in several key industrial sectors such as aerospace, automobile, marine, and defense, and the enhanced properties created by accumulative roll bonding will only increase its potential. The innovative approach described in this paper will be of interest to academic researchers and practitioners involved in new materials, processing, and product development.
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