生物醫(yī)用Ti-24Nb-4Zr-8Sn單晶合金塑性變形行為研究

生物醫(yī)用Ti-24Nb-4Zr-8Sn單晶合金塑性變形行為研究Plastic Deformation Behavior of Biomedical Ti-24Nb-4Zr-8Sn Single Crystal Alloy

針對具有特殊非線彈性變形行為的高強度低模量Ti-24Nb-4Zr-8Sn(質量分數，%，簡稱Ti2448)醫(yī)用鈦合金，采用光學浮區(qū)生長法制備出3種典型取向的低指數單晶，研究其塑性變形行為。結果表明，Ti2448單晶合金的室溫拉伸性能表現(xiàn)出明顯的各向異性，<100>取向、<110>取向和<111>取向單晶的抗拉強度分別為650、642和889 MPa，延伸率分別約為73%、22%和13%；單晶合金的室溫拉伸塑性變形機制以滑移為主，<100>取向單晶開動的滑移系統(tǒng)為(112)[11 ]、( 12)[1 1]、(1 2)[ 11]和(11 )[111]，<110>取向單晶開動的滑移系統(tǒng)為(211)[ 11]和( 11)[111]，<111>取向單晶開動的滑移系統(tǒng)為( 11)[111]；單晶合金沿<100>取向、<110>取向和<111>取向的拉伸樣品的斷口形狀分別呈現(xiàn)矩形狀、鴨嘴狀和三角狀，斷裂面與拉伸方向的夾角均約為55°，斷口均呈現(xiàn)韌性斷裂特征。

Ti-24Nb-4Zr-8Sn (mass fraction, %, abbreviated Ti2448) alloy is a multifunctional biomedical titanium alloy with high strength and low elastic modulus, which makes it show great application prospect in the field of body implant. It put up obvious nonlinear elasticity and highly localized plastic deformation behavior. Study on deformation behavior of single crystal can help understand the deformation mechanism of polycrystalline alloy. In this work, Ti2448 single crystal alloy along three different orientations were prepared by optical floating zone method. The plastic deformation behavior of them under tensile stress were investigated in terms of mechanical properties, slip system and fracture morphology. Results shows that Ti2448 single crystal shows obvious anisotropy, its tensile strength along <100>, <110> and <111> orientation is 650, 642 and 889 MPa, while the elongation is ~73%, ~22% and ~13%, respectively. The main plastic deformation mechanism of Ti2448 single crystal alloy is by slip. The appearance of slip bands and its direction relationship with crystal orientation were detailed observed. Under tensile stress, the operated slip system for <100>, <110> and <111> orientation is (112)[11 ]/( 12)[1 1]/(1 2)[ 11]/(11 )[111], (211)[ 11]/ ( 11)[111] and ( 11)[111], respectively. This is in accordance with the law of critical shearing stress. SEM analysis show a fracture surface shape of rectangle, duckbilled and triangle for the <100>, <110> and <111> orientation, respectively. The intersection angle between fracture surface and loading direction is all about 55 degree, and a lot of dimple was detected that show ductile fracture mode.

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