The effect of cooling rate on theβ-α transformation in the zirconium/2 at.% chromium/o.16 at.% iron alloy

• Published in: Journal of the less-common metals 1968, Vol.16 (2), p.91-101
• Main Author: Slattery, G.F.
• Format: Article
• Language: English
• ISSN: 0022-5088
• DOI: 10.1016/0022-5088(68)90066-0

The β-α transformation in the zirconium/2 at. % chromium/o. 16 at. % iron alloy shows two distinct temperature plateaux. The higher plateau at 760 °C is likely to be non-martensitic, whilst the lower plateau at 705 °C is probably martensitic and represents the true Ms temperature for this alloy. The separation between the two transformations is in the region of 1700 °C/sec cooling rate and beyond this critical cooling rate, the Ms temperature is independent of cooling rate up to 4500 °C/sec. Quench hardening takes place and an increase of 130 V.H. units is obtained with increase in cooling rate. The microstructures varied with cooling rate. At intermediate cooling rates, the structure consisted of a coarse Widmanstätten product which changed to a fine, acicular product with increase in cooling rate. The intermetallic phase, presumably ZrCr 2 associated with a very low iron concentration, acted as a nucleus for the shear needles of α′. There were no surface rumpling effects due to quenching out the martensitic structure but this may be explained by a shape change for the c.p.h.-b.c.c. transformation which involves only small, or adjacent and opposite displacements.