摘要
实验采用热等静压处理工艺作为选区激光熔化成形TA15钛合金试样的后处理手段,研究了不同热等静压温度对试样组织、硬度、裂纹扩展速率的影响规律。热等静压温度为900~980℃时,组织为多层级针状(条状)α组织,且随温度升高,针状(条状)α组织逐渐粗化,初级α相尺寸为60~66μm,宽度由2.35μm增加至5.62μm,材料硬度由35.8HRC降低至31.9HRC。热等静压温度为1 020℃,越过了α→β相变温度,形成魏氏组织,硬度为32.2HRC。当应力强度因子范围ΔK处于20~50 MPa·m^(1/2),不同热等静压工艺处理后试样的裂纹扩展速率趋于一致,受组织影响较小。当应力强度因子范围ΔK<20 MPa·m^(1/2),随热等静压处理温度升高,试样裂纹扩展速率逐渐降低,多层级针状(条状)α组织的粗化将增强对裂纹的偏转作用,阻碍裂纹扩展。热等静压温度为1 020℃形成的魏氏组织具有最低的裂纹扩展速率,不同位向的α集束利于使疲劳裂纹改变扩展方向,增大裂纹扩展路径长度,降低裂纹扩展速率。综上,较高温度热等静压处理后形成的粗化的多层级条状α组织或魏氏组织具有较低的裂纹扩展速率,但材料的硬度相对较低。
Selective laser melting(SLM)technology has attracted much attention from the aeronautics and astronautics realm due to its advantage of high degree of freedom,high accuracy,and good mechanical properties after printing.Considering the durability and designing concept of damage tolerance of structural materials,the crack propagation rate of components applied into aeronautics is regarded as one of the key points to ensure the service safety of equipment.The research of ameliorating the crack resistance of titanium alloys through posttreatment is believed to provide valuable data guidance to the further application of SLM-printed titanium-based components in the aeronautics.In the current paper,the hot isostatic pressing(HIP)process is conducted to SLM-printed TA15 alloys as the post-treatment.Specifically,the influence of the HIP temperature on the microstructure,hardness,and crack propagation rate are investigated in details.The microstructure of the as-printed TA15 alloy HIP treated at the temperature range of 900-980℃is generally identified as multi-hierarchical needle or lath-likeαphase.Besides,the size of theαphase gradually coarsens along with the rise of the HIP temperature.The average length of primaryαphase ranges from 60μm to 66μm.Whereas,the width of primaryαphase significantly increases from 2.35μm to 5.62μm.The hardness of the HIPed specimen resultantly reduces from 35.8 to 31.9(HRC).When the HIP temperature surpasses the phase transformation point ofαtoβphase,the formation of Widmannstatten structure is observed in the specimen with hardness of 32.2(HRC).The crack propagation rate of the specimens HIP treated utilizing different parameters converges and is seldomly affected by the microstructure when the stress intensity factor range(ΔK)is within 20~50 MPa·m^(1/2).While the crack propagation rate gradually decreases with the rise of HIP temperature whenΔK<20 MPa·m^(1/2).Coarsening of multi-hierarchical needle(lath)-likeαphase enhances the deflection of crack propagation path caused by microstructure,which correspondingly retards the further propagation of cracks.Widmannstatten structure formed in the specimen HIP treated at 1020℃possesses the lowest crack propagation rate among different microstructures.In addition,the packets ofαphase with various crystallographic orientation inside theβphase favors the conversion of fatigue cracks propagation path,which effectively lengthens the propagation path and reduces the crack propagation rate.In summary,the coarsened multi-hierarchical lath-likeαphase in the specimen HIP treated at 980℃and the Widmannstatten structure formed after HIP treatment at 1020℃benefit to the reduction of crack propagation rate.While the hardness of specimens suffers a certain loss.
作者
胡家齐
董定平
谢隋杰
蔡小叶
慈世伟
程宗辉
HU Jiaqi;DONG Dingping;XIE Suijie;CAI Xiaoye;CI Shiwei;CHENG Zonghui(State-owned Wuhu Machinery Factory,Wuhu 241000,China)
出处
《粉末冶金工业》
北大核心
2024年第5期67-73,共7页
Powder Metallurgy Industry
基金
安徽省重点领域补短板产品和关键技术攻关项目(JB21049)
关键词
热等静压处理
选区激光熔化
显微组织
洛氏硬度
裂纹扩展速率
hot isostatic pressing
selective laser melting
microstructure
rockwell hardness
crack propagation rate
