Finite Element Modeling and Experimental Validation of Microstructural Changes and Hardness Variation During Gas Metal Arc Welding of Aisi 441 Ferritic Stainless Steel

Grain growth and hardness variation occurring in high temperature Heat Affected Zone (HAZ) during the welding processes are two thermal dependant aspects of great interest for both academic and industrial research activities. This paper presents an innovative Finite Element (FE) model capable to describe the grain growth and the hardness decrease that occur during the Gas Metal Arc Welding (GMAW) of commercial AISI 441 steel. The commercial FE software SFTC DEFORM-3DTM was used to simulate the GMAW process and a user subroutine was developed including a physical based model and the Hall-Petch (H-P) equation to predict grain size variation and hardness change. The model was validated by comparison with the experimental results showing its reliability in predicting important welding characteristics temperature dependant. The study provides an accurate numerical model (i.e. user subroutine, heat source fitting, geometry,…) able to successfully predict the thermal phenomena (i.e. coarsening of the grains and hardening decrease) that occur in the HAZ during welding process of ferritic stainless steel.

Fractional Recrystallization Behavior of Impurity-Doped Commercially Pure Aluminum

This manuscript reports the effects of trace impurities on the fractional recrystallization behavior of commercially pure aluminum. To allow the recrystallization cold rolled by 75% alloy samples are annealed isothermally at 700ºK for different time up to 60 minutes. Recrystallization kinetics is evaluated from the micro hardness variation of the different annealed samples. The JMAK type analysis is also used to study the recrystallization behavior as well as to observe the correlation with the experimental results. The behavior of the fraction recrystallization between two methods the trace impurities added alloys is evidence for the higher variation as to form GP zones and metastable phases during annealing. Higher addition shows the more variation as the formation of higher fraction phases. The microstructural study reveals that annealing at 700ºK for 30 minutes the alloys attain almost fully re-crystallized state.