TC6 alloy is a martensitic Ti-Al-Mo-Cr-Fe-Si system α+β two-phase heat-strength titanium alloy with good comprehensive properties, and its nominal composition is Ti-6Al-2.5Mo-1.5Cr-0.5 For Fe-0.3Si, the α/β transition temperature is between 960 and 1000°C. In addition to the advantages of high specific strength and good corrosion resistance of ordinary titanium alloys, this alloy also has good comprehensive mechanical properties at room temperature and high temperature, and the service temperature can be as high as 450°C. Components can also be used to manufacture parts such as bulkheads and joints of aircraft. Domestically, a lot of work has been done on the processing technology and performance optimization of TC6 titanium alloy forgings, castings, pipes and rods, etc., but there are few studies on TC6 alloy plates. Researchers have determined by controlling the cold rolling process of TC6 plates. The basic process parameters of TC6 sheet cold rolling processing were studied, and the cold rolling processing performance of TC6 sheet was studied.
The TC6 titanium alloy ingot used in the experiment is obtained by three times of smelting in a vacuum consumable electric arc furnace. Its β transformation temperature is 975-985°C, and its specific chemical composition is (wt.%): Al6.2, Mo2.5, Cr1.4 , Fe0.41, Si0.29, O0.10, Zr<0.01, C<0.01, N<0.01, Ti balance. The TC6 ingot used in the experiment was opened in the β-phase region, and the α+β two-phase region was forged into a slab. The slab was hot-rolled above the β transition temperature and rolled to 3.5mm in the α+β two-phase region. After intermediate annealing and pickling, the cold rolling work hardening test was carried out. When the processing rate increases by 5%, cut a piece of 200mm long test material from the head of the plate, and continue rolling the remaining plate, and repeat rolling and sampling in this way until edge cracks or surface cracks appear on the plate. Then the cut 200mm experimental materials with different processing deformations were tested, and the thickness, width, edge crack, structure and mechanical properties of the experimental plates were tested respectively.
The above-mentioned experimental microstructure was observed on an Axiovert 200 MAT optical microscope, and the mechanical properties were tested on an Instron5885 tensile testing machine. The test results are as follows:
(1) From the cold rolling work hardening curve, it can be found that the tensile strength and yield strength increase with the increase of processing rate, while the elongation decreases gradually, which is mainly due to the increase of dislocation density with the increase of cold rolling processing rate , work hardening intensifies. When the processing rate reaches about 27%, the tensile strength and yield strength curves tend to be horizontal, indicating that it has entered the stage of difficult deformation.
(2) The maximum cold rolling processing rate of TC6 titanium alloy plate can reach 30.3%, at this time, the elongation of the material drops to 5.8%, and it is observed that the surface of the plate begins to appear wrinkles and embossments, and cracks appear on the edge. When the cold rolling processing rate reaches 30.3%, the width is 20mm.