Microstructure evolution, tensile properties and internal structure transformation study on Ti6Al4V–5Cu anti-bacterial alloy during uniaxial tensile straining at low forming temperature

Abstract

The tensile behavior of Ti6Al4V–5Cu alloy studied in the temperature range of 450–550 °C at the strain rate interval of 10−3-10−1 s−1. Alloy deformation behavior, microstructure evolution, and its relative internal structure changes due to deformation were investigated. The tensile behavior of the alloy had elucidated in terms of change in true stress-strain relationship. At 450 °C, the alloy showed the decrease of peak stress at the strain rate interval of 10−3-10−2 s−1, which suggests Ti6Al4V–5Cu plastic flow behavior, was quite different. The alloy exhibited an elongation (El) of 28% at 450 °C in a strain rate of 10−3 s−1. At 10−3 s−1, the El of the alloy decreased with the increase of forming temperature. However, at 10−2 s−1 and 10−1 s−1, the El increased with the rising of temperature. Scanning electron microscope (SEM) was used to investigate the microstructure of Ti6Al4V–5Cu alloy. The alloy grain boundaries (GBs) were found as continuous and discontinuous structural features, especially the high angle grain boundaries (HAGBs). The GB feature has contributed to the initiation of micro-cracks because of the creation of weakest regions in the material during deformation. The nature of GB geometry has also a tremendous contribution to the workability of Ti6Al4V–5Cu alloy at low forming temperatures. The presence of a high amount (%) LAGBs and the serrated nature of HAGBs structures determined the pull to grain pieces. The deformation mechanism of the Ti6Al4V–5Cu alloy at low forming temperatures was accomplished initially by boundary serration phenomenon due to strain-induced GB migration related to heat treatment at low strain condition, then by initiation of recrystallized grains-triggered by the plasticity behavior of strain induced sub-boundaries, and finally by the development of deformed grains generated by the reduction in corrugation propensity of GBs due to high strain condition.