摘要
In order to obtain high-density dual-scale ceramic particles(8.5 wt.%SiC+1.5 wt.%TiC)reinforced Al-Mg Sc-Zr composites with uniform microstructure,50 nm TiC and 7μm SiC particles were pre-dispersed into 15−53μm aluminum alloy powders by low-speed ball milling and mechanical mixing technology,respectively.Then,the effects of laser energy density,power and scanning rate on the density of the composites were investigated based on selective laser melting(SLM)technology.The effect of micron-sized SiC and nano-sized TiC particles on solidification structure,mechanical properties and fracture behaviors of the composites was revealed and analyzed in detail.Interfacial reaction and phase variations in the composites with varying reinforced particles were emphatically considered.Results showed that SiC-TiC particles could significantly improve forming quality and density of the SLMed composites,and the optimal relative density was up to 100%.In the process of laser melting,a strong chemical reaction occurs between SiC and aluminum matrix,and micron-scale acicular Al_(4)SiC_(4) bands were formed in situ.There was no interfacial reaction between TiC particles and aluminum matrix.TiC/Al semi-coherent interface had good bonding strength.Pinning effect of TiC particles in grain boundaries could prevent the equiaxial crystals from growing and transforming into columnar crystals,resulting in grain refinement.The optimal ultimate tensile strength(UTS),yield strength(YS),elongation(EL)and elastic modulus of the SiC-TiC/Al-Mg-Sc-Zr composite were~394 MPa,~262 MPa,~8.2%and~86 GPa,respectively.The fracture behavior of the composites included ductile fracture of Al matrix and brittle cleavage fracture of Al_(4)SiC_(4) phases.A large number of cross-distributed acicular Al_(4)SiC_(4) bands were the main factors leading to premature failure and fracture of SiC-TiC/Al-Mg-Sc-Zr composites.
铝基复合材料因其具有高比强度和高比模量等优点,作为关键的轻量化结构材料而备受关注。但其切削加工难度大,不利于近净成形。本文采用激光选区熔化(SLM)技术,制备了高密度双尺度陶瓷颗粒(8.5 wt.%SiC(微米级粒径)+1.5 wt.%TiC(纳米级粒径))增强Al-Mg-Sc-Zr复合材料。通过微观组织表征和力学性能测试,研究了激光能量密度、功率和扫描速率对复合材料密度的影响规律;阐明了微米级SiC和纳米级TiC颗粒对复合材料凝固组织、力学性能和断裂行为演变的作用机理;重点分析了不同颗粒增强复合材料的界面反应和相变化。结果表明,SiC-TiC颗粒能显著提高SLM铝基复合材料的成形质量和密度,最佳相对密度可达100%。在SLM过程中,SiC颗粒与Al基体发生强烈的化学反应,原位形成微米尺度的针状Al_(4)SiC_(4)条带。TiC颗粒与Al基体之间没有界面反应。TiC/Al半共格界面具有良好的结合强度。TiC颗粒在晶界处的钉扎作用可以阻止等轴晶的生长和向柱状晶的转变,从而使晶粒细化。SiC-TiC/Al-Mg-Sc-Zr复合材料的最佳极限抗拉强度、屈服强度、伸长率和弹性模量分别为~394 MPa、~262 MPa、~8.2%和~86 GPa。复合材料的断裂行为表现为Al基体的韧性断裂和Al_(4)SiC_(4)相的脆性解理断裂。大量交叉分布的针状Al_(4)SiC_(4)条带是导致SiC-TiC/Al-Mg-Sc-Zr复合材料过早失效断裂的主要因素。
基金
Project(2022J318)supported by the Natural Science Foundation of Ningbo,China
Project(2021A1515110525)supported by the Guangdong Basic and Applied Basic Research Foundation,China
Project(2022QN05023)supported by the Inner Mongolia Natural Science Foundation Youth Project,China。
作者简介
Corresponding author:MA Guo-nan,PhD,Associate Researcher,E-mail:Ma_Guonan@163.com,ORCID:https://orcid.org/0009-0000-9026-6934。
