【作者】 杜立明；

【导师】 彭德林；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 本文分别采用金属粉末注射成形工艺（Metal Injection Molding,MIM）和熔铸原位合成法制备（TiB+TiC）/Ti基复合材料。在MIM工艺中研究了粉末与粘结剂选择及配比、喂料制备、注射成型、脱脂、烧结等工艺。熔铸原位合成法中,对材料的组织性能进行了研究。将高纯度的B₄C粉以质量分数2.4%加入到Ti粉中,和石蜡基粘结剂体系混炼成成分均匀并具有一定流动性的喂料,然后制粒。混炼时加入硬脂酸（SA）作为表面活性剂以改善粘结剂对粉末的润湿性。注射工艺中,模具温度为40℃、注射压力为150 MPa、保压压力为120MPa、注射温度为140℃。分别采用三氯乙烷、二硫化碳及汽油进行常温下溶剂脱脂,三者的平均脱脂率分别为56.4%、65.3%、63.4%。当脱脂至坯块重量不再变化时,三者的时间分别为60h、30h、20h。脱脂后的断口分析显示,成形坯内粘结剂大部分脱除,粉末之间的通道被打开,坯块内形成了连通孔隙。采用真空烧结工艺,真空度达到1×10-2Mpa,先以10℃/min升温至200℃,保温5min再以2.3℃/min升至550℃,保温20min,这时残留的粘结剂被彻底脱除。继续升温,最后达到1240℃,分别在800℃、1000℃、1240℃温度下保温40min、60min、60min,随后试样随炉缓冷。B₄C在钛中所占质量分数分数分别为2.5%、2.8%、2.9%,采用纽扣式非自耗电极熔炼炉熔炼。分别对熔铸原位法合成及真空烧结后的材料试样进行SEM、金相显微组织分析及XRD相组成分析,两者的组织基本一致,在高温下B₄C和Ti发生反应生成TiB和TiC。TiB和TiC分布在钛基体上,能谱分析表明等轴状或近于等轴状为TiC增强相,针状或短棒状的为TiB增强相。熔铸原位法合成的增强相分布比较均匀,MIM工艺制备的增强相分布相对不均匀。TiB和TiC增强相生成后,复合材料的硬度、压缩强度相比钛基体及Ti-6Al-4V合金有了很大提高,并且随着TiB和TiC的增加,材料的压缩强度、硬度也随之增加。压缩断口显示,断口上存在较多的剪切韧窝,宏观压缩断口与作用力呈45°角,表明断裂属于韧性断裂。高温氧化结果表明,TiB和TiC提高了材料的抗氧化性。更多还原

【Abstract】 In this paper, （TiB+TiC）/Ti matrix composites were obtained by metal powder injection molding （Metal Injection Molding, MIM） and cast in-situ synthesis. In the MIM process, the selection and proportion of the powder and binder, preparation of feedstock, injection molding, debinding, sintering and other processes were studied. For cast in-situ synthesis, microstructure and properties of the materials were researched .The B₄C powder of high purity was mixed into Ti powder by the mass fraction of 2.4%, and then mixed with paraffin-based binder system to be made into tempered homogeneous and liquid feedstock, and then granulating. When mixing, stearic acid （SA） was added as a surfactant to improve the wettability of the powder binder. In the injection process, the mold temperature was 40℃, injection pressure was 150MPa, holding pressure was 120MPa, injection temperature was 140℃, then degreased at room temperature by trichloroethane, carbon disulfide, and gasoline which have an average of debinding ratio is 56.4%, 65.3%, 63.4% respectively, When the weight of sample was no longer change, the time was 60h, 30h, 20h respectively. After the process of degreasing, the result of fracture analysis showed that the majority of forming blanks within the binder was removed, the channel was opened between the powders, and the pores was formed. When vacuum sintering, vacuum was 1×10-2 Mpa or more, the temperature was firstly heated to 200℃by 10℃/min, heat preservation for 5min and then rose to 550℃by 2.3℃/min, heat preservation for 20min, then the residual binder would be completely removed from the system. Continue to heat up, and finally to 1240℃, heat preservation for 40min, 60min, 60min at 800℃, 1000℃, 1240℃respectively, then followed by slow cooling the samples with the furnace.B₄C mass fraction of titanium in the share were 2.5%, 2.8%, 2.9%, with button-type non-self-consumable electrode melting furnace smelting. The specimens properties were studied using SEM, metallographic microstructure analysis, XRD.The result showed that this two materials have the same organization, TiB and TiC at high temperatures produced by the reaction B₄C and Ti. TiB and TiC were distributed in the titanium matrix, the energy spectrum analysis showed that the equiaxed or near equiaxed reinforcements were TiC, and needle-like or short rod for TiB. The reinforcement produced by cast in-situ synthesis is distributed more evenly, while the reinforcement prepared by MIM is relatively asymmetry distribution.The hardness and compressive strength have been greatly improved compared to titanium substrate and the Ti-6Al-4V alloy when TiB and TiC reinforcement were created into the composite, the compressive strength and hardness of the material were enhanced along with the increase of TiB and TiC too. The result of compression fracture showed that there are more shear fracture dimples, and the macro-compression fracture is 45°angle with the forces which indicates the fracture is ductile. The result of high temperature oxidation showed that TiB and TiC have improved the antioxidant activity.更多还原