TC4 titanium rod forging process analysis

Large deformation resistance of titanium alloy, chemically active, thus forging process has special problems and difficulties. First, the microstructure and properties of titanium forgings for forging thermal parameters are very sensitive. Titanium forging temperature range is relatively narrow in the forging process, with the increase of strain rate, its deformation resistance increased significantly, showing a strong strain rate sensitivity. Second, the thermal conductivity of titanium alloys is poor, in the forging process prone to localized overheating, resulting in a large temperature difference between inside and outside, inside and outside the degree of deformation of the blank exacerbate uneven distribution, resulting in cracking the forging process, and in severe cause product obsolescence. Therefore, studying the effects of different forging process on the microstructure and mechanical properties of titanium alloys, to seek a reasonable forging process to forming titanium forgings production has important practical significance.

TC4 titanium alloy have excellent performance in the aerospace, automotive and medical and other fields has been widely used, is the most widely used as a two-phase α + β type titanium alloy. Scholars of the various properties and processing technology titanium launched a lot of research, however, the system of different forging process on TC4 alloy microstructure and mechanical properties of a few. Researchers studied the β forging, forging close β and (α + β) two-phase region forging affect three different bars forging process on microstructure and mechanical properties of TC4 titanium alloy microstructure, more optimization program with a view to forging process selected for Production TC4 titanium alloy forgings to meet the requirements to provide a reference.

TC4 alloy material size experiment is Φ100mm × 450mm of forging stock, as measured by optical method (α + β) / β transformation point (Tβ) to 990 ℃.

In order to study the influence of the forging process on microstructure and mechanical properties of TC4 Titanium Alloy, forging stock will be divided into three sections, namely conventional forging (Tβ-60 ℃), near-β forging (Tβ-20 ℃) ​​and β forging (Tβ + 40 ℃) process test, deformation of 50%. Forging equipment for 3t free forging hammer. After forging, the process to get through three kinds of forging 900 ℃ × 1h / AC + 600 ℃ × 4h / AC dual heat treatment. After the heat treatment, the TC4 titanium alloy forgings intercept metallographic sample, tensile specimens and impact test specimens, the microstructure was observed under the microscope. Using image analysis software to complete and other microstructure parameters axis α phase content and secondary slice thickness α phase of quantitative statistics. The results showed that:

(1) TC4 alloy forged by α + β, near β and β forging three kinds of forging process after forging, respectively equiaxed structure, mixed structure and lamellar tissue.

(2) α + β forging, strength after forging close β and β forging TC4 titanium alloy bars fairly, but after forging and near α + β β β forging forging relatively high plasticity, but β forging TC4 titanium rod Best toughness. After nearly β forging TC4 titanium alloy bars show the best mechanical properties.

(3) tensile specimen fracture TC4 titanium alloy bars under three kinds of forging process showed a ductile fracture mechanism, α + β forging and near-β forging with deep and evenly distributed equiaxed dimples, and β forging alloy exhibits a more flat and elongated dimples.