Microstructure and tensile properties of novel Zr-Cr binary alloys processed by hot rolling

Zr-Cr alloys with Cr content of 0.5, 1.5, 1.8 to 3.0 at% were processed by hot rolling followed by subsequent water quenching. The phase transformation, microstructure evolution and the tensile properties of the processed Zr-Cr alloys were investigated. The metallographical results indicated that the width of α-Zr lamellae was sensitive to Cr content. The average lamella width gradually decreased with increasing Cr content in the Zr-Cr alloys. This was attributed to the growing number of second-phase α-ZrCr2 particles pinning the grain boundaries and the fact that the alloys with a lower phase transformation temperature had fewer time to grow. Uniaxial tensile tests were conducted to evaluate the mechanical properties of the alloys. The Zr100−xCrx (x=3.0, at%) alloy possessed the highest ultimate tensile strength (1270 MPa) with an elongation of 6.0%. Compared to the ultimate tensile strength of pure Zr (718 MPa), this demonstrates that adding Cr to pure Zr can greatly improve the tensile properties. Furthermore, the paper illuminates the equiaxied grain formation mechanism and the strengthening mechanism in Zr-Cr alloys.