Anomalous strain rate dependence of ultra-low temperature strength and ductility of an electron beam additively manufactured near alpha titanium alloy  

作　　者：H.Z.Niu S.Liu M.C.Zang D.L.Zhang P.Cao W.X.Yang 

机构地区：[1]School of Materials Science and Engineering,Northeastern University,Shenyang 110819,China [2]Xi'an Rare Metal Materials Institute Co.Ltd.,Xi'an 710016,China [3]Department of Chemical and Materials Engineering,The University of Auckland,Auckland 1142,New Zealand

出　　处：《Journal of Materials Science & Technology》2024年第31期44-55,共12页材料科学技术(英文版)

基　　金：supported by the National Natural Science Foundation of China(No.52271026);the Applied Basic Re-search Program of Liaoning province(No.2023JH2/101300158);the Fundamental Research Fund for the Central Universities(No.N2202010).

摘　　要：The strain rate()dependence of ultra-low temperature strength and ductility was investigated systematically on a cryogenic near alpha titanium alloy Ti-3Al-3Mo-3Zr-0.2Y additively manufactured by electron beam selective melting(EBSM).As increases under quasi-static tension at 77 and 20 K,ductility monotonically decreases when yield strength(YS)keeps ascending.As increases from 5.6×10^(-4) s^(-1) once by one order of magnitude,elongation-to-fracture declines from 20.0%to 16.5%and 15.7%at 20 K.However,unlike the regular monotone increase at 298 and 77 K,ultimate tensile strength(UTS)at 20 K rises to 1460 MPa first then drops to 1320 MPa.This study further examined how strain rate affects slipping,twinning and strain hardening behavior.The monotone increase in YS is primarily attributed to the increased CRSS for slips and the enhanced tendency of pyramidal〈a〉and〈c+a〉slipping and<100>34°twinning at 20 K.On the other hand,the monotone decrease of ductility is essentially ascribed to the intensified deformation localization characterized by micro shear bands,multiple necking and single necking.More importantly,the mechanisms of abnormal UTS variation and disappearance of serration flow at 20 K are discussed in terms of strain hardening levels,degree of shear deformation localization and the interaction of slips and twins.This study provides deep insights into strain rate effect on cryogenic mechanical behavior of EBSM-built titanium alloy.

关 键 词：Titanium alloy Additive manufacturing Strain rates Ultra-low temperature tensile properties Deformation mechanism 

分 类 号：TG1[金属学及工艺—金属学]