【摘要】：鈦合金TC4(Ti-6Al-4V)是目前應用最為廣泛、最有前景的生物醫(yī)用鈦合金之一,如何提高其加工性能及其他理化性能以滿足生物醫(yī)用領域的需求,是亟待解決的關鍵技術問題。本文研究了高能電脈沖在鈦合金TC4的加工處理及表面改性過程中的應用及其相關機理。首先,通過研究高能電脈沖處理冷加工鈦合金TC4的局部再結晶過程發(fā)現(xiàn),電脈沖處理后鈦材的斷裂伸長率平均提高113.5%,而鈦材的強度幾乎沒有變化,同時力學性能的各向異性明顯降低,微觀組織由初始沿軋向分布的條狀晶粒轉變?yōu)闆]有明顯取向性的等軸晶粒。接著,通過研究高能電脈沖處理冷加工鈦合金TC4的完全再結晶和織構演變發(fā)現(xiàn),電脈沖明顯降低層片狀加工孿晶的退化、非基面取向的再結晶晶粒生長和織構演變的表觀溫度,通過建立電脈沖過渡段上的熱力學和動力學模型,發(fā)現(xiàn)當表觀溫度高于門檻值時(366℃)電脈沖的非熱效應在完全再結晶和退孿晶過程中逐漸占據(jù)主導地位,該結論與實驗結果比較吻合。然后,通過研究高能電脈沖處理熱加工層片狀組織鈦合金TC4的相變球化過程發(fā)現(xiàn),高能電脈沖能顯著提升材料的塑性(132.4%),同時能促進熱加工層片組織的相變過程β-Ti→α-Ti并形成細小的等軸化微觀組織。另外,通過研究高能電脈沖在材料表面制備納米氧化鈦層的過程中,發(fā)現(xiàn)在表面形成的具有微波型氧化鈦顯微粗糙表面和類骨蜂窩狀納米孔結構的金紅石型氧化鈦層增強了材料的耐腐蝕性能和生物相容性,電脈沖的電磁場效應和熱效應加快了氧化速率(較傳統(tǒng)熱表面氧化速率高兩個數(shù)量級),降低了氧化層的厚度。最后,探索了電脈沖(輔助)加工制備高性能鈦合金的工藝:高能電脈沖輔助超聲沖擊表面處理(電沖擊)和高能電脈沖輔助軋制(電軋)過程。通過研究發(fā)現(xiàn),電沖擊能夠通過動態(tài)再結晶和相變過程誘導納米晶和β相的生成,同時加大了表面塑性流變的影響深度和程度,進一步增大了材料表面硬度和耐磨性;電軋工藝通過動態(tài)再結晶過程弱化進入軋輥前材料的基面織構、誘導晶粒方向橫向偏轉、增加中間取向差角晶界,從而降低加工溫度和變形抗力,提高成材質量和綜合力學性能。
[Abstract]:Titanium alloy TC4 (Ti-6Al-4V) is one of the most widely used and promising biomedical titanium alloys. How to improve its processing performance and other physical and chemical properties to meet the needs of biomedical field is a key technical problem to be solved urgently. In this paper, the application of high energy electric pulse in the process of processing and surface modification of titanium alloy TC4 and its related mechanism are studied. Firstly, by studying the local recrystallization process of cold working titanium alloy TC4 treated by high energy electric pulse, it is found that the average elongation at break of titanium is increased by 113.5%, but the strength of titanium is almost unchanged. At the same time, the anisotropy of mechanical properties was obviously decreased, and the microstructure changed from the initial stripe grain to the equiaxed grain with no obvious orientation. Then, by studying the complete recrystallization and texture evolution of TC4 treated by high energy electric pulse, it is found that the degradation of lamellar processing twins and the apparent temperature of recrystallization grain growth and texture evolution of non-base-oriented recrystallized titanium alloys are obviously reduced by electrical pulse. By establishing thermodynamic and kinetic models of electric pulse transition, it is found that the non-thermal effect of electric pulse (366 鈩，

本文編號：2195561