Hande Güler

Influence of Heat Treatment Parameters on the Microstructure and Mechanical Properties of Boron-Alloyed Steels

Abstract This paper focuses on the effect of heat treatment parameters on the microstructure and mechanical properties of quenchable 22MnB5 steel sheets with an Al–Si layer. Heat treatment parameters such as temperature and cooling rate from the solid solution temperature were investigated. For this purpose, the heat treatment was conducted within the temperature range from 700°C to 950°C, and two different cooling techniques were applied to the specimens: air cooling and water quenching. The microstructures of the specimens were then studied using optical microscopy. Additionally, tensile and hardness tests were performed at room temperature. The results show that the effects of heat treatment were obviously influenced by the original microstructure of the 22MnB5 sheet. With the increase of heat treatment temperature, the martensite proportions increased, and the hardness and tensile strength also increased, especially after the 850°C quenching. Moreover, quenching after 900°C has been reached was determined to be an ideal process for hot forming 22MnB5 steel sheets.

Investigation of the tool effect on the strength of friction stir spot welded aluminum specimens: A comparative study

Abstract Aluminum and its alloys are widely used in the automotive industry because of their light weight and good formability as well as malleability, and an alternative welding technique, the friction stir spot welding process, can be successfully used to join these materials. In this study, friction stir spot welding is applied to an AA 5754-H111 alloy to compare the effect of tool geometry and tool material on shear strength. Welds are made using different rotational speeds of tool and dwell times ranging from 500 to 1500 rpm and 6 s to 21 s, respectively. The experimental results showed that the combination of dwell time and rotational speed of tool as well as tool geometry and tool material have an important role in the strength of the joints. The total thickness and weld nugget diameter were also investigated in this study.