When the tantalum and tantalum alloy are prepared by powder metallurgy sintering method, more oxygen will be absorbed on the surface of the powder. During high temperature sintering, oxygen diffusion solves, resulting in higher oxygen content of the material as a whole. Although the strength is improved, the plasticity drops sharply. For example, Ta-7.5W alloy prepared by powder metallurgy sintering process, after pressure processing into wire and plate, although the strength can reach a high level of 1170MPa, but its elongation is greatly damaged, only about one sixth of the melted alloy. By using low-oxygen pre-alloyed Ta-10W alloy powder, the dense material prepared by hot isostatic pressing has the same strength as the smelted alloy. Therefore, there is no more suitable method to further improve the strength of tantalum and macroalloy. The low strength makes people have to increase the amount of materials, which causes tantalum alloy application scope is greatly limited.
Tantalum or tantalum alloy cast ingots with low impurity content were prepared by electron beam vacuum melting process, and powder was produced by hydrogenation dehydrogenation process. The powder was heated to 30(TC ~ 8O0 'c for several times at low oxygen partial pressure (10 -- 'Pa ~ 10'Pa)
Surface aeration treatment, so that the powder surface formed gas solid solution or low tantalum oxygen compound; Then the pre-treated tantalum powder was sealed into the envelope and solidified by hot isostatic pressure at the temperature of 1300'C ~ 1500'C and the pressure of 150MPa ~ 200MPa to obtain the dense bulk material. After removing the jacket, vacuum heat treatment was carried out at a higher temperature (180(TC ~ 240(TC)) to adjust the material.
Mechanical properties of Tantalum alloy sintered strip with TA-9.2W-0.5 HF was used to produce alloy ingot by electron beam vacuum melting. After hydrogenation, crushing and dehydrogenation, 100 mesh ~ 300 mesh powder was obtained by screening. After multiple low oxygen partial pressure oxygenation treatment at 300'C ~ 800'C, surface hardened superalloy powder particles were obtained. The total oxygen content of powder increased from 0.02% to 0.15%. The powder was first formed by cold isostatic pressing with the relative density of 65%. Then the cold isostatic pressing blank was put into the tantalum envelope, and the hot isostatic pressing was processed after sealing welding. The hot isostatic pressing pressure was 200MPa and the temperature was 130(TC) for 4 hours, to obtain the block material with a relative density of 98.8%. The mechanical properties of the material at room temperature are as follows: tensile strength 1303MPa, yield strength 1269MPa, elongation 4.6% and section shrinkage 15%, which are 125% and 164% higher than those of annealed smelted rolled material with the same composition, and 69% and 76% higher than those of processed smelted rolled material.
