Influence of heat treatment process on microstructure and mechanical properties of TLM titanium tube

Abstract:

An alloy with the normal composition of Ti-25Nb-3Zr-3Mo-2Sn (TLM) has been prepared using cold-rolling technology for application as a thin tube material with a size of Φ4.0×0.3mm. The heat treatment process has been carried out for TLM in temperature range of 933、993K and follow by aging treatment at 783K. The effects of heat treatment and aging process for TLM on the microstructure and mechanical properties have been investagted by metallogical microscopy, X-ray diffraction and mechanical measurement at room temperature. The column-like crystals can be observed at any heat-treatment temperature. The average grain sizes increase with increasing temperature. The phase transition from β+α' to α occurs in TLM. The analysis reveals that the mechanical property depends on heat treatment temperature, which is due to the phase transition induced by temperature. The phase transition are dynamic, which can be described as β+α'→β+α'+α→β+α. The presention of α phase is benefical for improving the tensile strength and elastic modulus and declining the elongation ratio. The fine property can be otaioined at 993K, 0.5h (ST) +783K, 3h (AT).

Key words:β-type titanium alloy; TLM; small diameter thin-tube; organization; mechanical properties