Ultra comprehensive metallographic diagrams of titanium and titanium alloys

 

Alpha titanium alloys are divided into full alpha alloys and near alpha alloys; Industrial pure titanium belongs to alpha alloys. In addition, alpha alloys generally contain about 6% Al and a small amount of neutral elements. After annealing, almost all of them are alpha phase. Typical alloys include TA1~TA7 alloys, etc; In addition to a small amount of neutral elements, there are also a small amount (not exceeding 4%) of alpha stable elements in near alpha alloys, such as TA16 and TA17 alloys. 

 

According to the national standard GB/T3602.1-2007, industrial pure titanium is classified into 9 grades based on impurity element content, including TA1, TA1ELI, TA1-1, and TA2, with a phase transition point of 900 ℃. Industrial pure titanium is mainly used in applications that require high plasticity, appropriate strength, good corrosion resistance, and weldability. They have good cold and hot processing performance and can produce various specifications of plates, bars, profiles, strips, pipes, and foils. Generally delivered for use in annealed state. The mechanical properties of pure titanium sheet specified in the national standard GB/T3621-2007 are shown in Table 1-1. The microstructures of TA1, TA2, and TA3 are shown in Figures 1-1 to 1-5. Table 1-1 Mechanical Properties of Pure Titanium Plate (GB/T3621-2007) 

 

Figure 1-1 TA1 plate annealed at 650 ℃/1h microstructure: equiaxed α+a small amount of intergranular β (dark)

Figure 1-2 TA3 sheet annealed at 800 ℃/1h microstructure: equiaxed α+transformation with needle shaped α

Figure 1-3 TA2 Large Specification Bar Material 600 ℃/1h Annealed Microstructure: Isometric α

Figure 1-4 TA2 precision forged bar material annealed at 600 ℃/1h microstructure: equiaxed α

Figure 1-5 Incomplete recrystallization microstructure of TA3 sheet annealed at 450 ℃/1h: a small amount of equiaxed α+elongated strip-shaped α

 

 

 

 

The nominal composition of TA16 alloy is Ti-2Al-2.5Zr (Russian grade nT-7M), which is a near alpha titanium alloy developed by the former Soviet Union with a phase transition point of 940 ℃. The alloy has good cold processing technology and welding performance, and is widely used in ship power systems and aviation pipeline systems. Table 1-2 lists the mechanical properties of TA16 alloy wire in the annealed state. The microstructure of TA16 alloy is shown in Figures 1-6 to 1-14.
Table 1-2 Tensile Properties of TA16 Alloy Φ 4mm Wire after Annealing at 700 ℃/1h

 

Figures 1-6 to 1-11 show the microstructure of TA16 alloy wire with a diameter of 4mm after hot drawing and annealing at different temperatures, as well as the microstructure of the processed state with different deformation amounts. Figures 1-12 to 1-14 show the microstructure of TA16 alloy plate after hydrogenation treatment.

Figure 1-6: The microstructure of TA16 alloy wire in the processed state shows elongation of the alpha phase

Figure 1-7 TA16 alloy wire, annealed at 700 ℃ for 1 hour, shows the α equiaxed microstructure and a small amount of intergranular β (dark)

Figure 1-8 TA16 alloy wire, annealed at 900 ℃ for 1 hour, shows the α equiaxed microstructure and a small amount of intergranular β (dark)

Figure 1-9 Deformation microstructure of TA16 alloy wire during processing (600 ℃, total strain 5%), with elongation of alpha phase

Figure 1-10 Deformation microstructure of TA16 alloy wire during processing (600 ℃, total strain 30%), with elongation of alpha phase

Figure 1-11 Deformation microstructure of TA16 alloy wire during processing (800 ℃, total strain 30%), exhibiting dynamic recovery characteristics

12 TA16 alloy sheet was subjected to hydrogenation treatment at 600 ℃, with a hydrogen content of 570 × 10-6. The black dots were TiH, and brittle cracks were generated during the tensile process of the sample

Figure 1-13 TA16 alloy sheet undergoes hydrogenation treatment at 600 ℃, with a hydrogen content of 990 × 10-6. The black dots are TiH, and brittle cracks are generated during the tensile process of the sample

Figure 1-14: The weld seam of TA16 alloy sheet was subjected to hydrogenation treatment at 600 ℃, with a hydrogen content of 990 × 10-6. The black dots were TiH, and brittle cracks were generated during the tensile process of the sample

 

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