简单退火和多重热处理对激光熔覆成形Ti-5321合金断裂韧性的影响  

Effect of Single Annealing and Multiple Heat Treatment on Fracture Toughness of Ti-5321 Alloy Prepared by Laser Cladding Forming

作　　者：刘国政 赵永庆[1,2] 贾蔚菊[2] 张艳[1,2] 宋硕[1,2] 毛成亮 周伟 Liu Guozheng;Zhao Yongqing;Jia Weiju;Zhang Yan;Song Shuo;Mao Chengliang;Zhou Wei(Northeastern University,Shenyang 110819,China;Northwest Institute for Nonferrous Metal Research,Xi’an 710016,China)

机构地区：[1]东北大学,辽宁沈阳110819 [2]西北有色金属研究院,陕西西安710016

出　　处：《稀有金属材料与工程》2024年第4期970-977,共8页Rare Metal Materials and Engineering

基　　金：National Key Technologies Research and Development Program of China(2021YFC2801901)。

摘　　要：为满足航空航天领域对快速制备高强韧复杂钛合金零件的需求,采用激光熔覆成形新型高强韧Ti-5321(Ti-5Al-3Mo-3V-2Zr-2Cr-1Nb-1Fe)合金,具有成形快、效率高、成形构件性能良好等优势。通过对Ti-5321合金进行简单退火和多重热处理(β相区固熔缓冷加时效,BASCA),揭示了其显微组织的演变规律,并探究不同组织对断裂韧性的影响。结果表明:简单退火后,合金呈细长针片状α交织成的网篮组织,其抗拉伸强度为1102 MPa,断裂韧性为68.1 MPa·m^(1/2)。经BASCA热处理后,细长针片状α相全部转变为粗大的片层α相和超细针状α相,且合金的抗拉伸强度提高至1309 MPa,而断裂韧性降低至45.5 MPa·m^(1/2)。BASCA热处理能够提高合金强度,但会降低合金韧性。这是由于网篮组织中细长的针片状α相能够大大增加裂纹扩展阻力,增大裂纹扩展路径曲折程度,从而提高合金的韧性。而BASCA热处理组织中大片层α相具有一定的方向性,裂纹只有在穿过不同β晶粒的大片层α相时才会发生偏转;且裂纹扩展主要发生在超细针状α相中,而超细针状α相尺寸过于细小,不能阻碍裂纹的发展或使裂纹偏转,因此经BASCA热处理后合金的韧性变差。In order to satisfy the requirements of aerospace field for rapid preparation of high strength and toughness complex titanium alloy parts,new Ti-5321(Ti-5Al-3Mo-3V-2Zr-2Cr-1Nb-1Fe)alloy with high strength and high toughness was prepared by laser cladding forming,which possesses the superiority of rapid prototyping,high efficiency,and good formability.Through single annealing and multiple heat treatment(β-annealing with slow cooling and aging,BASCA)on Ti-5321 alloy,the microstructure evolution was revealed,and the influence of different microstructures on the fracture toughness was explored.Results show that after single annealing,the alloy morphology presents the basket-weave structure consisting of elongated lamellarαphases.Its ultimate tensile strength is 1102 MPa,and fracture toughness is 68.1 MPa·m^(1/2).After BASCA heat treatment,the elongated lamellarαphase changes to coarse lamellarαphase and ultrafine needle-likeαphase.Thus,the ultimate tensile strength increases to 1309 MPa,whereas the fracture toughness reduces to 45.5 MPa·m^(1/2).BASCA heat treatment can enhance the strength but degrade the toughness of alloys.This is because the elongated lamellarαphase in basket-weave structure can greatly increase the crack growth resistance and aggravate the tortuous degree of crack growth path,thus improving the alloy toughness.Coarse lamellarαphase after BASCA heat treatment has a certain degree of directionality,and the cracks only deflect when passing through the coarse lamellarαphase of differentβgrains.Crack propagation mainly occurs in the ultrafine needle-likeαphase.However,due to the extremely small size of ultrafine needle-likeαphase,it cannot hinder the development of crack path or deflect the cracks.Thus,the toughness of coarse lamellar structure becomes more inferior after BASCA heat treatment.

关 键 词：激光熔覆成形 Ti-5321合金 多重热处理 断裂韧性 

分 类 号：TG665[金属学及工艺—金属切削加工及机床] TG146.23[一般工业技术—材料科学与工程] TG156.2[金属学及工艺—金属材料]