Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
J Mech Behav Biomed Mater. 2014 Apr;32:310-320. doi: 10.1016/j.jmbbm.2013.10.027. Epub 2013 Nov 11.
The effect of swaging on the Young's modulus of β Ti-33.6Nb-4Sn rods was investigated by X-ray diffraction, thermography, microstructural observations, deformation simulator analysis and cyclic tensile deformation. Stress-induced α″ martensite was stabilized by swaging, dependent on the diameter reduction rate during swaging. Thermography and deformation simulator analysis revealed that swaged rods were adiabatically heated, and consequently, stress-induced α″ underwent reverse transformation. Young's modulus, which was measured by the slope of the initial portion of the stress-strain curve, decreased from 56GPa in the hot-forged/quenched rod to 44GPa in the rapidly swaged rod with a high reduction rate and to 45GPa in the gradually swaged rod with a low reduction rate. The tangent modulus, which was measured by the slope of the tangent to any point on the stress-strain curve, decreased with strain even in the linear range of the stress-strain curve of the hot-forged/quenched rod and the rapidly swaged rod, while the tangent modulus remained unchanged for the gradually swaged rod. It was found that Young's moduli in swaged β Ti-33.6Nb-4Sn rods were affected by stabilized α″ martensite. Low Young's modulus of 45GPa and high strength over 800MPa were obtained when the reverse transformation by adiabatic heating was suppressed and the stress-induced α″ was sufficiently stabilized by gradual swaging to a 75% reduction in cross section area.
通过 X 射线衍射、热成像、微观结构观察、变形模拟器分析和循环拉伸变形研究了挤压对β Ti-33.6Nb-4Sn 棒材杨氏模量的影响。挤压通过直径减小率稳定了应变速诱α″马氏体。热成像和变形模拟器分析表明，挤压棒材被绝热加热，从而导致应变速诱α″发生反向转变。通过应力-应变曲线初始部分的斜率测量的杨氏模量，从热锻/淬火棒的 56GPa 降低到高减径率的快速挤压棒的 44GPa，以及低减径率的逐渐挤压棒的 45GPa。切线模量通过在应力-应变曲线上的任何点的切线斜率测量，即使在热锻/淬火棒和快速挤压棒的应力-应变曲线的线性范围内也会随应变而降低，而逐渐挤压棒的切线模量保持不变。发现挤压β Ti-33.6Nb-4Sn 棒材的杨氏模量受稳定的α″马氏体影响。当抑制绝热加热的反向转变并通过逐渐挤压将应变速诱α″充分稳定到截面积减小 75%时，可获得杨氏模量为 45GPa 和强度超过 800MPa 的低杨氏模量。
