双重退火对近α钛合金组织及力学性能的影响OA

Ti6321 alloy,a near-α titanium alloy independently developed in China,has become a key structural material for marine engineering because of its high strength,high toughness and outstanding seawater-corrosion resistance.Nevertheless,under conventional heat treatment its strength and ductility are difficult to balance,restricting its use in deep-sea extreme environments.In this work,ship-grade Ti6321 alloy was subjected to single annealing(970,980,990,1000℃for 2 h,air cooled)and duplex annealing(980℃for 2 h,air cooled,then 550℃or 600℃for 2 h,air cooled).The effects of these an-nealing routes on microstructure and mechanical properties were systematically investigated by optical microscopy(OM),scanning electron microscopy(SEM)and mechanical testing.The results revealed that single annealing produced the typical α+β two-phase microstructural evolution,with the best strength-toughness combination obtained at 980℃.Duplex annealing refined the microstructure by precipitating secondary α phases within and along the boundaries of the β-transformed structure,anneal-ing treatment at 980℃+550℃markedly increased both strength and toughness.This study provides a theoretical basis for optimizing the heat treatment process of Ti6321 alloy for marine engineering ap-plications.