Ti-1023 is a typical near-β titanium alloy, which has attracted extensive attention for such particular advantages as good damage tolerance and deeper hardenability as compared with its congeners. It needs systemic relationship of microstructure and properties for the application of Ti-1023 alloy, so that we can gain the right properties to meet request by many ways. The objective of this paper is to systemically research the effects of microstructure including primary α phase (αp) and secondary α phase (αs) on tensile properties and fracture toughness in Ti-1023 alloy by different heat treatment to achieving the relationship of various microstructure and mechanical properties.
In the study, it was found that the volume fraction of αp plays the main role in influencing the tensile properties while the αp morphology plays the minor role. Under solution heat treatment (ST) condition, tensile strength decreases with the decrease of the volume fraction of αp; Under solution and aging heat treatment (STA) condition, both the strength and fracture toughness exhibit the increase tendency with the decrease of the αp volume fraction, but the increase amplitude for fracture toughness was far less than that for strength. That the decrease of the αp volume fraction causes the increase of the solute atom concentration in metastable β phase and the growth of β grain size is used to explain the above-mentioned effects of αp . Pronounced effect of secondary α phase (αs) on improving tensile strength is observed. With the growth of αs size and the decrease of its amount, the strengthening effect of αs was found to decrease, but fracture toughness and tensile ductility were obviously improved. The better combination of fracture toughness and tensile strength in Ti-1023 alloy can be achieved by way of lowering αp volume fraction, controlling appropriate αs amount and its size，reducing the continuous grain boundary α as possible and avoiding excessive growth of continuous grain boundary α phase.
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