The ductility of a HSLA steel at temperatures below 300 K

High Strength Low Alloy (HSLA) steel exhibits good ductility at low temperatures down to 77 K in both ferrite-pearlite and dual-phase structures. The instantaneous strain-rate sensitivity (m) increases with decreasing temperature and reaches a maximum at 100 K. This peak temperature is much lower than that for plain carbon steels. The post-uniform elongation, which is more sensitively dependent onm, shows only slight increase around 100 K. The effect ofm on the post-uniform elongation is probably mitigated by the increasing dependence ofm on strain rate above 180 K. The uniform elongation, normally associated with the strain hardening characteristics of the material, also shows some increase around 100 K. Therefore, both strain-hardening and strain-rate hardening are responsible for the enhanced ductility of HSLA steel around 100 K.