Jeffrey Venezuela

A review of hydrogen embrittlement of martensitic advanced high-strength steels

Abstract The martensitic advanced high-strength steels (MS-AHSS) are used to create fuel-efficient, crashworthy cars. Hydrogen embrittlement (HE) is an issue with high-strength steels; thus, the interaction of hydrogen with MS-AHSS needs to be studied. There are only a few published works on the HE of MS-AHSS. The current literature indicates that the HE susceptibility of MS-AHSS is affected by (i) the strength of the steel, (ii) the applied strain rate, (iii) the concentration of hydrogen, (iv) microstructure, (v) tempering, (vi) residual stress, (vii) fabrication route, (viii) inclusions, (ix) metallic coatings, and (x) specific precipitates. Some of the unresolved issues include (i) the correlation of laboratory results to service performance, (ii) establishing the conditions or factors that lead to a certain HE response, (iii) studying the effect of stress rate on HE, and (iv) a comprehensive understanding of hydrogen trapping in MS-AHSS.

A review of the influence of hydrogen on the mechanical properties of DP, TRIP, and TWIP advanced high-strength steels for auto construction

Abstract The literature is reviewed regarding the influence of hydrogen on dual-phase (DP), transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) steels. Hydrogen influences DP steels by decreasing ductility while strengths are largely unaffected. TRIP steels may be susceptible to hydrogen embrittlement (HE) as indicated by the loss of ductility and some brittle fracture features. The literature on the influence of hydrogen on TWIP steels was inconsistent. Some researchers found no significant influence of hydrogen on TWIP steel properties and fully ductile fractures, whereas others found a significant loss of ductility and strength due to hydrogen and some brittle features. Possible countermeasures for HE are tempering for DP and TRIP steels and aluminum alloying for TWIP steels.

Evaluation of automobile service performance using laboratory testing

ABSTRACT A methodology is presented to evaluate martensitic advanced high-strength steels in auto service. There was essentially no influence of hydrogen for (i) linearly increasing stress tests of specimens with hydrogen contents much greater than for automobile service, and (ii) for tensile tests with simultaneous hydrogen charging and with a substantial hydrogen content. These results allow evaluation of the hydrogen influence for the tested steels for auto service. In contrast, electrochemically hydrogen charged martensitic advanced high-strength steels showed an influence of hydrogen on mechanical properties, manifest as (i) a decrease in yield strength, by hydrogen enhanced macroscopic ductility, and (ii) a change of the micro-fracture mode, by hydrogen-assisted micro-fracture.