Research Project Abstract: The purpose of this study is to investigate the mechanical properties of a five-element based HEA. The study will observe the microstructures and mechanical properties of multi-principal (or HEA) CoCrFeNiTi. The CoCrFeNiTi alloy displayed a crystalline structure constructed by a simple face-centered cubic solid solution (low in Titanium). The secondary phases consisted of FCC (60.95%), a chi phase (22.4%), a Laves phase (14.79%), and very small appearances of sigma and R phases within the face-centered cubic matrix of the as-casted CoCrFeNiTi alloy. The hardness value of the alloy decreased after the homogenizing heat treatments. Historically, alloys with Titanium content have shown high yield stress values and low ductility values. The solid-solution strengthening of the face-centered cubic matrix and the secondary- phase hardening were the two main factors that strengthened the alloy. When heat treatments were applied (see table a), the CoCrFeNiTi alloy displayed reduced hardness as the secondary phases were decreased. The original as-casted sample came with a hardness measured at 551 HV. The sample with the longest homogenizing heat treatment (48 hr @ 1100 deg Celsius) came in with the lowest hardness measured (200 HV). Interestingly, when the CoCrFeNiTi was homogenized at 1150 degrees Celsius for 24 hours, the FCC phase increased to 89.22% of the total secondary phases.

Video made by David Pepper about his research results and experience in this RET program (Click Here)

Lesson plan submitted to TeachEngineering: Mechanical & Thermal Tests on Materials (Status: under review)