Three-dimensional hydrogen distribution and quantitative determination of titanium alloys via neutron tomography

For the first time, neutron tomography was applied for 3D quantitative hydrogen distribution analysis in titanium alloys following thermohydrogen processing.

Thermohydrogen Processing of 3D Screen Printed Titanium Parts

The present study addresses the need for grain refinement in free sintered titanium alloys produced by 3D screen printing. Thermohydrogen processing (THP) was used for temporary alloying Ti-6Al-4V with hydrogen to refine its microstructure. The impact on microstructure was investigated by a parameter study with varying temperatures, exposure times and hydrogen partial pressures. Heat treated specimens were examined by optical microscopy, XRD and thermal analysis. The influence of the refined microstructure on the mechanical properties was evaluated by tensile and microhardness testing. Ultrafine grained microstructures with ultimate tensile strengths of up to more than 1000 MPa could be produced.

Submicron Grain Size Formation in Thermohydrogenated and Deformed Ti-6Al-4V: The Effect of Processing Route on the Degree of Grain Refinement

The aim of this work was to refine the as-cast Ti-6Al-4V grain size and its Widmanstätten morphology to optimise the mechanical performance of Ti-6Al-4V castings. Hydrogenation and deformation were used as variables in processing routes aimed at assessing the degree of refinement in the as-cast Ti-6Al-4V microstructure. Thermohydrogen processing (THP) refined the Widmanstätten morphology and not the prior beta grain boundary network. Therefore, the degree of refinement in THP processing is limited to morphology refinement within pre-existing prior beta grains. Deformation processing and recrystallisation is necessary to eliminate the indelible influence of the prior beta grain boundary network on the extent of THP refinement. In this context, a substantial degree of refinement is achieved from thermohydrogen and deformation processing (THDP). The as-cast Ti-6Al-4V grain boundary network was refined from an average diameter of 2000μm to 20μm. In addition, the Widmanstätten morphology was refined to submicron equiaxed alpha and beta grains.

Studies of Ti-15V-3Cr-3Al-3Sn after Thermohydrogen Processing

Ti-15V-3Cr-3Al-3Sn, β-phase titanium alloy, is subjected to study the microstructure and mechanical behavior after thermohydrogen processing. It aims to study the relationship between microstructure modification and notched tensile test at room temperature. Meanwhile, the notched tensile test and fracture features of Ti-15-3 alloy without THP is also discussed. It follows that the hardness of Ti-15V-3Cr-3Al-3Sn would be clearly enhaced up to Hv 499 after thermohydrogen processing due to grain refinement. Besides, the notched tensile strength of the as-received specimen is about 904 MPa, and is increased to 959 MPa after THP, that is, Ti-15-3 alloy after THP shows higher hardness and notched tensile strength than as-received alloy. The enhanced high hardness does not induce a significant notched embrittlement effect.

Linear Friction Welding Performance of Hydrogenated Ti-6Al-4V Alloy

The linear friction welding (LFW) performance of hydrogenated Ti-6Al-4V alloy was investigated. The effects of hydrogen on macro-features and axial shortening as well as microstructure of Ti-6Al-4V alloy joints welded by LFW were analyzed. The mechanical properties of joints after dehydrogenation were also examined by tensile test at room temperature. The results indicated that the hydrogenated Ti-6Al-4V specimens containing 0.3~0.4 wt% hydrogen had a better microstructure and plastic deformation ability, which resulted in the optimum welding performance improvement of LFW. The critical power input of LFW could be lowered by addition of hydrogen to Ti-6Al-4V alloy. The results of tensile test showed that joints which experienced thermohydrogen processing possessed the same tensile strength and plasticity as original joints.