Experimental and Theoretical Design of Advanced High-Entropy Alloys and Application in Al-Fe Dissimilar Welding

Weight reduction is always an important topic in the automobile industry, for energy and natural resource savings. To achieve this goal, a lot of studies have been conducted on the dissimilar welding to join aluminum with steel. In the present work, a novel idea is come up to apply high-entropy alloys as interlayers into the dissimilar welding between aluminum and steel. In the past decades, high-entropy alloys (HEAs) have drawn great attention due to their unique single-phase microstructures and outstanding mechanical properties as structural materials. In this work, three tasks are come up for the investigation: using current HEAs on the dissimilar welding, design HEAs with desired properties based on the prior work, and conduct welding study and analysis on dissimilar welding with designed HEAs.

In the first task, the Al0.1CoCrFeNi and Al0.3CoCrFeNi HEAs are selected to be the interlayers. The insights obtained in this study offer an understanding of how the current face-centered cubic (FCC) HEAs will work on dissimilar welding. In the second task, due to the problems that exist in the first task, new HEAs that fit with the dissimilar welding need to be developed. In order to fulfill this task and find out the best HEAs for trial, a technique, high throughput calculation (HTC) which is based on calculations of phase diagrams (CALPHADs), is applied for the search of the vast compositional space of HEAs. New HEAs with desired properties are designed, fabricated, and characterized. In the third task, a welding study is conducted with the designed HEAs. Solidification analysis with CALPHAD is conducted, based on the model came up by Dr. Sindo Kou. A criterion for solidification cracking is applied to evaluate the susceptibility. The present work shows that with newly designed HEAs by the second task, a fusion zone with the mixing of the aluminum alloys, steel, and HEAs is obtained for the first time. New HEA compositions are proposed for future work.