Effect of TiB_(2)Addition on Microstructure and Mechanical Properties of AA8009 Alloy Fabricated by Laser Additive Manufacturing

The research involves the addition of 5 vol.%TiB_(2)particles into AA8009 alloy powder to synthesize TiB_(2)/AA8009 composite parts produced via laser powder bed fusion(LPBF).The addition of the TiB_(2)particles causes the TiB_(2)/AA8009 composites with and without annealing have lower compressive strength than AA8009 alloy due to the change of the strengthening mechanism.The results further indicated that solid solution strengthening was the main strengthening mechanism of the LPBF AA8009 alloy at room temperature whereas Orowan strengthening became the primary strengthening factor after annealing at 673 K.In contrast,Orowan strengthening always remained the main strengthening mechanism for the TiB_(2)/AA8009 composite,irrespective of the annealing temperature.In addition,after annealing of the LPBF parts at 673 K,the compressive yield strength(CYS)of the unblended AA8009 alloy specimens had a~2.5 times greater reduction(from 705±16 to 459±30 MPa)compared to that of the composite TiB_(2)/AA8009 samples(from 466±23 to 368±3 MPa).Therefore,TiB_(2)particles can suppress the drop in yield strength of LPBF AA8009 alloy below 673 K,providing a theoretical and experimental basis for the applications of both LPBF AA8009 and TiB_(2)/AA8009 alloys at low and medium temperatures.

Selective Laser Melting of Al-7Si-0.5Mg-0.5Cu:Effect of Heat Treatment on Microstructure Evolution,Mechanical Properties and Wear Resistance

Al-7Si-0.5Mg-0.5Cu alloy specimens have been fabricated by selective laser melting(SLM).In this study,the effects of solution treatment,quenching,and artifi cial aging on the microstructural evolution,as well as mechanical and wear properties,have been investigated.The as-prepared samples show a heterogeneous cellular microstructure with two different cell sizes composed ofα-Al and Si phases.After solution-treated and quenched(SQ)heat treatment,the cellular microstructure disappears,and coarse and lumpy Si phase precipitates and a rectangular Cu-rich phase were observed.Subsequent aging after solution-treated and quenched(SQA)heat treatment causes the formation of nanosized Cu-rich precipitates.The asprepared SLMs sample has good mechanical properties and wear resistance(compressive yield strength:215±6 MPa and wear rate 2×10^(-13)m^(3)/m).The SQ samples with lumpy Si particles have the lowest strength of 167±13 MPa and the highest wear rate of 6.18×10^(1-13)m^(3)/m.The formation of nanosized Cu-rich precipitates in the SQA samples leads to the highest compressive yield strength of 233±6 MPa and a good wear rate of 5.06×10^(-13)m^(3)/m.

Whole-exome sequencing of a multicenter cohort identifies genetic changes associated with clinical phenotypes in pediatric nephrotic syndrome

Understanding the association between the genetic and clinical phenotypes in children with nephrotic syndrome(NS)of different etiologies is critical for early clinical guidance.We employed whole-exome sequencing(WES)to detect monogenic causes of NS in a multicenter cohort of 637 patients.In this study,a genetic cause was identified in 30.0%of the idiopathic steroid-resistant nephrotic syndrome(SRNS)patients.Other than congenital nephrotic syndrome(CNS),there were no significant differences in the incidence of monogenic diseases based on the age at manifestation.Causative mutations were detected in 39.5%of patients with focal segmental glomerulosclerosis(FSGS)and 9.2%of those with minimal change disease(MCD).In terms of the patterns in patients with different types of steroid resistance,a single gene mutation was identified in 34.8%of patients with primary resistance,2.9%with secondary resistance,and 71.4%of children with multidrug resistance.Among the various intensified immunosuppressive therapies,tacrolimus(TAC)showed the highest response rate,with 49.7%of idiopathic SRNS patients achieving complete remission.Idiopathic SRNS patients with monogenic disease showed a similar multidrug resistance pattern,and only 31.4%of patients with monogenic disease achieved a partial remission on TAC.During an average 4.1-year follow-up,21.4%of idiopathic SRNS patients with monogenic disease progressed to end-stage renal disease(ESRD).Collectively,this study provides evidence that genetic testing is necessary for presumed steroid-resistant and idiopathic SRNS patients,especially those with primary and/or multidrug resistance.