Microstructure and mechanical properties of ultralow carbon high-strength steel weld metals with or without Cu-Nb addition

Two types of ultralow carbon steel weld metals(with and without added Cu-Nb) were prepared using gas metal arc welding(GMAW) to investigate the correlation between the microstructure and mechanical properties of weld metals.The results of microstructure characterization showed that the weld metal without Cu-Nb was mainly composed of acicular ferrite(AF), lath bainite(LB), and granular bainite(GB).In contrast, adding Cu-Nb to the weld metal caused an evident transformation of martensite and grain coarsening.Both weld metals had a high tensile strength(more than 950 MPa) and more than 17% elongation;however, their values of toughness deviated greatly,with a difference of approximately 40 J at-50℃.Analysis of the morphologies of the fracture surfaces and secondary cracks further revealed the correlation between the microstructure and mechanical properties.The effects of adding Cu and Nb on the microstructure and mechanical properties of the weld metal are discussed;the indication is that adding Cu-Nb increases the hardenability and grain size of the weld metal and thus deteriorates the toughness.

Outcomes of Ebstein＇s Anomaly Patients Treated with Tricuspid Valvuloplasty or Tricuspid Valve Replacement：Experience of a Single Center

Background：The incidence of Ebstein＇s anomaly is extremely low,and except for the Mayo Clinic,no cardiac center has reported on a sufficient number of patients.The aim of our study was to report the outcomes of Ebstein＇s anomaly patients treated with tricuspid valvuloplasty （TVP） or tricuspid valve replacement （TVR）.Methods：TVP or TV R was performed in 245 patients from July 2006 to April 2016.We reviewed patients＇ records and contacted patients via outpatient service and over the telephone.Results：The mean follow-up time was 43.6 ± 32.6 months,and 224 （91.4％） patients underwent follow-up.The mean operative age was 31.2 ± 15.7 years.TVR was performed in 23 patients,and TVP was performed in 201 patients.The 30-day mortality rate was 1.3％,and the overall survival rate was 97.9％ at 5 and l0 years.The early mortality rate of the TVP group was lower than that of the TVR group （0.5％ vs.8.7％,P =0.028）,and the overall mortality rate of the TVP group was lower than that of the TVR group,without statistical significance （1.0％ vs.8.7％）.After propensity score matching,the rates of mortality and New York Heart Association class ≥Ⅲ were lower in the TVP group than those in the TVR group without statistical significance.Seven patients with Type B Wolff-Parkinson-White （WPW） syndrome underwent one-stage surgery,and arrhythmias disappeared.Six patients suffered from episodes of left ventricular outflow tract obstruction （LVOTO） during surgery.Severe LVOTO could be treated with reoperation of the atrialized right ventricle.Conclusions：Ebstein＇s anomaly patients treated with TVP or TVR can experience optimal outcomes with midterm follow-up.However,TVP should be the first-choice treatment.Optimal outcomes can be obtained from one-stage operation in patients with Type B WPW syndrome.Severe LVOTO during surgery might be related to improper operation of the atrialized right ventricle.