首页|Formation and characteristics of bilamellar microstructure in Ti6242S titanium alloy under dual heat treatment
Formation and characteristics of bilamellar microstructure in Ti6242S titanium alloy under dual heat treatment
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NSTL
Elsevier
? 2022 Elsevier Inc.The formation and characteristics of bilamellar microstructure in Ti6242S titanium alloy under a dual heat treatment (single-phase heat treatment + two-phase heat treatment) were investigated. Heated at single β region and cooled by the air, when the grain boundary α (αGB) kept BOR (Burgers orientation relationship) with the β matrix on both sides, more grain boundary Widmansta¨tten α (αWGB) clusters were generated. The cooling modes after single-phase region heat treatment will change the source of the primary lamellar α, β → α phase transition or martensite decomposition. During two-phase heat treatment, the secondary lamellar α nucleates at the β grain boundaries or the wide interface of the primary lamellar α and the existing primary lamellar α facilitates the formation of the secondary lamellar α with same or similar orientation, showing a typical intragranular Widmansta¨tten α(αWI) microstructure. The V-shaped lamellar α with an angle of about 60° is precipitated from the martensite and shows a V-cone shape in three-dimensions. When the holding time is prolonged to 60 min, three α variants grow simultaneously and keep a mirror relationship in pairs, forming a triangular structure which has a pyramid shape in three dimensions. Variant selection occurred in the lamellar microstructure during dual heat treatment. Held at subsequent two-phase region, the primary lamellar α with the misorientation angle of 90° preferentially dissolved, increasing the variant selection. The primary lamellar α provided nucleation sites for the secondary lamellar α, leading to a decrease of variant selection.
NSTL
Elsevier
