Bake-hardening behaviour of carbon steel with different martensite morphologies and volume fraction was investigated. The specimens with fibrous and bulky martensite were prestrained in tension by 4%. After this, they...Bake-hardening behaviour of carbon steel with different martensite morphologies and volume fraction was investigated. The specimens with fibrous and bulky martensite were prestrained in tension by 4%. After this, they were unloaded and bake hardened at 180 ℃ for 10-160 min. It was found that dual-phase steel samples which were bake hardened at 180 ℃ for 20 rain showed an increase in the yield stress （YS） and ultimate tensile stress （UTS） but a decrease in ductility. Further increase in the bake-hardening time of 80 or 160 min has reduced the YS and UTS, but increased the ductility. △σ （increase in stress due to bake hardening）, YS and UTS values are higher for the microstructure containing fibrous martensite compared to the microstructure-containing bulky martensite. It was also observed that at a given baking temperature Aa, YS and UTS increased by volume of martensite.展开更多
文摘Bake-hardening behaviour of carbon steel with different martensite morphologies and volume fraction was investigated. The specimens with fibrous and bulky martensite were prestrained in tension by 4%. After this, they were unloaded and bake hardened at 180 ℃ for 10-160 min. It was found that dual-phase steel samples which were bake hardened at 180 ℃ for 20 rain showed an increase in the yield stress （YS） and ultimate tensile stress （UTS） but a decrease in ductility. Further increase in the bake-hardening time of 80 or 160 min has reduced the YS and UTS, but increased the ductility. △σ （increase in stress due to bake hardening）, YS and UTS values are higher for the microstructure containing fibrous martensite compared to the microstructure-containing bulky martensite. It was also observed that at a given baking temperature Aa, YS and UTS increased by volume of martensite.
