TZM Alloy Research Articles

Enhanced ductility and thermal stability of TZM alloys via nanoscale second phase

In this study, molybdenum alloy with the nanoscale second phase dispersion distribution (NM-TZM) was prepared by powder metallurgy. Despite maintaining a high yield strength of 893 MPa, the elongation of the as-forged MN-TZM alloy has been increased to 25.3 %. In addition, the recrystallization start temperature of NM-TZM alloy was increased by 100 °C, reaching 1400 °C. The nanoindentation results indicate that the NM-TZM alloy still exhibits a high hardness of 4.40 GPa following annealing at 1400 °C. The addition of nanoscale second phase can improve the ductility and high temperature stability of the alloy by coupling with dislocations and grain boundaries. A new model for the synergistic effect of grain boundaries and intragrains to improve ductility is proposed, which provides insight into the reason behind the high ductility of NM-TZM.

Analysis of High and Low Temperature Performance of Titanium Zirconium Molybdenum Alloy and High Temperature Alloy Brazed Joint

Abstract Using niobium as the intermediate layer and gold nickel (Au82-Ni) filler metal, TZM alloy and high-temperature alloy GH3128 were brazed. The brazed specimens were subjected to 400 cycles of high and low temperature cycling tests at temperatures ranging from 650 °C ∼ 680 °C (high temperature) to -196 °C (low temperature) for 10 minutes seperately. Then the microstructure variation before and after the experiment were observed and the shear strength of the specimens were tested at room temperature for 50 cycles of 400 high and low temperature testing.. The results show that the microstructure of the transition zone at the brazing interface after brazing is uniform and dense, with good wettability with the substrate and no defects such as cracks. The solder and substrate undergo diffusion reactions, and the molybdenum alloy, niobium, and niobium, high-temperature alloy had each form diffusion layers, formed intermetallic compounds on the brazing surface. After high and low temperature cycling, cracks exist in the braze seam between molybdenum alloy and niobium alloy. The cracking mode should be thermal fatigue based on the fracture morphology and phase analysis. The reasons of interface cracking are that due to different thermal expansion coefficients, low mutual solid solubility, and the formation of a large number of different types of intermetallic compounds, Mo and Nb materials have poor brazing compatibility and lower interface strength. Under cold and hot cycling conditions, brittle intermetallic compounds are prone to form crack source areas. As the number of cycles increases, the cracks gradually expand, ultimately leading to product leakage. In addition, the shear strength of brazed joints shows a decreasing trend with the increase of high and low temperature cycles in 400 high and low temperature tests.

Enhanced mechanical properties of TZM alloy via doping Y2O3 along with creating heterogeneous grain structures

The further application exploration of TZM alloys have been hindered by the limited strength especially at high temperatures. Herein, we propose a strategy to enhance the mechanical properties of TZM alloys by introducing heterostructures through Y2O3 doping combined with rotary forging (RF). The particle stimulated nucleation (PSN) mechanism promotes fine grains (FGs) nucleate close to the micron-sized second phase particles. The mechanical properties of Y2O3-TZM (YTZM) alloy are improved through the synergistic strengthening influence of back stress strengthening and second phase strengthening. The ultimate tensile strength (UTS) of YTZM at room temperature and 1000 °C is 820 MPa and 433 MPa, respectively, which are about 15% and 51% higher than that of TZM. In addition, the FCC-oxides generated by adding Y2O3 can trigger twinning, stacking faults, and 9R structures during high-temperature deformation, and the long-period stacked ordered phase (LPSO) nucleates at the stacking faults and twin boundaries through the 9R structures, which is more conducive to alleviate the stress concentration at the oxide/matrix interface and improve the dislocation blocking ability. The present strategy provides a paradigm for the development of high-performance TZM alloys through creating heterostructures.

Effect of hot isostatic pressing on microstructure and mechanical properties of TZM alloy formed by powder metallurgy

Abstract TZM alloy billets were fabricated using powder metallurgy (PM) and powder metallurgy + hot isostatic pressing (PM+HIP) techniques, and the influence of these two processes on the microstructure and mechanical properties of TZM alloy billets was compared. The experimental findings indicate that an enhanced hot isostatic pressing process effectively reduces the internal porosity of TZM alloy, leading to increased tensile strength and elongation at room temperature. However, there is no significant improvement in hardness and tensile strength at 600℃.

Synergistic enhancement of strength-ductility balance of TZM alloy through c-ZrO2 combined with large deformation and annealing

In this work, new TZM alloys containing 0.5 wt% and 1.0 wt% ZrO2 were prepared by powder metallurgy method, and their annealed microstructures and mechanical properties were studied. The TZM alloy sheet with 94 % deformation was recrystallized at 1200°C, and the elongation was greatly increased, and its UTS, YS and EL were 573 ± 10 MPa, 431 ± 7 MPa and 44 ± 0.2 %, respectively. After adding 0.5 wt% c-ZrO2, the best strength-ductility balance was achieved, and its UTS, YS, EL and PSE are 621 ± 3 MPa, 527 ± 4 MPa, 41.3 ± 0.58 % and 25.6 GPa·%, respectively, which was much larger than the PSE combinations of most Mo and TZM alloys. Microstructure analysis shows that the excellent synergistic effect arises from the low O impurity content and the control of dislocation density and dislocation slip by c-ZrO2 and the annealing process. Within the alloy, Ti and Zr react with O to produce TiO2 and ZrTiO4, which reduces the content of O impurities. Annealing provides sufficient space for dislocation slip, which coordinates the rotation of grain orientation during the stretching process. Coupled with the low O impurity concentration, results in excellent ductility of TZM alloys. Additionally, c-ZrO2 can effectively fix dislocations within the grains and interact strongly with dislocations, consequently enhancing the strength of the TZM alloy.

Improved structure and enhanced properties of detonation sprayed W coating via hot isostatic pressing

Tungsten has garnered significant attention for its superior performance as a plasma-facing material in tokamak devices. However, its hardness and high ductile-to-brittle transition temperature present challenges for its application in plasma-facing components. To address these issues, this study employs the detonation spraying (DS) technique to prepare tungsten coatings on a TZM alloy substrate and further optimizes their properties through hot isostatic pressing (HIP) treatment. Advanced characterization techniques were utilized to conduct a detailed microstructural and compositional analysis of the coatings. The results indicated that the HIP treatment significantly reduced the porosity of the coatings, improving their density and overall quality. Additionally, HIP treatment led to a decrease in internal stress, a reduction in dislocations, and the grain growth within the coatings. The study also discussed how the HIP process improved the microstructure of the DS tungsten coatings through these mechanisms, thereby enhancing the coatings' thermodynamic properties. Mechanical property tests revealed that the coatings treated with HIP exhibited higher bonding strength and lower hardness, attributed to the increase in grain size and the reduction in dislocation density within the coatings. Thermal property tests demonstrated that the HIP-treated coatings possessed higher thermal diffusivity and specific heat capacity in the temperature range of 100 to 500 °C. Furthermore, the performance of the coatings under transient high heat flux conditions was significantly improved after the HIP treatment, showing better resistance to the thermal shock and cracking. These findings are of great importance for understanding the performance enhancement of DS tungsten coatings in nuclear fusion reactor applications via HIP, especially as candidate materials for the first wall of tokamak devices.

Effects of filler materials on the microstructural characteristics and mechanical properties of laser-welded lap joints of TZM alloys

The poor weldability of molybdenum (Mo) alloys has always been the main problem that impedes their application as large-sized structural components. Two types of laser-welded lap joints, namely LW-Ti and LW-Nb joints, were prepared using titanium (Ti) and niobium (Nb) as filler materials to investigate the alterations in microstructures and mechanical properties of TZM (Mo-0.5Ti-0.08Zr-0.02C) alloy joints. The results indicate that both Ti and Nb have excellent metallurgical compatibility with Mo, resulting in well-formed joints. Due to solid-solution strengthening, the microhardness of the fusion zone (FZ) significantly increases from 269.9 HV to 397.1 HV for LW-Ti joints and reaches 389.6 HV for LW-Nb joints. Furthermore, the shear strength of LW-Ti joints is approximately 2.05 times that of LW-Nb joints, measuring at 110.97 MPa. Fractures in LW-Ti joints primarily occur at the base metal (BM) and display lamellar ductile fracture characteristics, while fractures in LW-Nb joints mainly occur at the FZ and exhibit coarse brittle intergranular fractures. The mechanical properties of LW-Nb joints are compromised due to the larger maximum pore diameter (300 μm) in the FZ compared to LW-Ti joints (50 μm), which can be attributed to the higher viscosity of liquid niobium. Additionally, the average grain size in the FZ of LW-Nb joints (86.37 μm) is larger than that in LW-Ti joints (53.28 μm). The reduction in grain size observed in LW-Ti joints also increases the grain boundary area, decreases oxygen concentration along the grain boundaries, and enhances binding strength at Mo grain boundaries. Given Ti's stronger affinity for oxygen compared to Mo, the abundant formation of second-phase TiO2 particles within LW-Ti joints hinders the specific formation of MoO2 along grain boundaries. Consequently, the proposed welding technology was employed to weld a large-scale cylinder-flange component made from Mo alloy, which is expected to greatly facilitate the widespread utilization of welded structures made from Mo alloys.

Investigation on the recrystallization and mechanical properties of a novel TZM alloy with heat treatment

The objective of this investigation is to ascertain the initial recrystallization temperature range for a novel Mo-TiC-ZrC-C (TZM) alloy. Annealing experiments were conducted on the TZM alloy rolled sheet, revealing an initial recrystallization temperature of 1100 °C. In the temperature range of 1100 ∼ 1150 °C, there were notable changes in yield strength (11 %), tensile strength (13 %) and elongation (19 %). Due to the varying effects of annealing temperature and recrystallization within distinct temperature ranges, the average grain size of the TZM alloy exhibits an initial increase followed by a decrease in the range of 900 ∼ 1200 °C. At 1200 °C, a noteworthy enhancement in recrystallized grains is observed.

Enhancing the oxidation resistance of TZM alloy by laser-clading MoSi2-TiVAlZrNb composite coating

The MoSi2 coating is an ideal coating system for molybdenum alloys due to the formation of a SiO2 glass phase and its good oxidation resistance in high-temperature service environments. However, the difference in the thermal expansion coefficient between MoSi2 and molybdenum alloy results in cracks in the MoSi2 coating, which has an important effect on the oxidation resistance at high temperature. In this paper, MoSi2 coatings were optimized by the addition of a multicomponent TiVAlZrNb on a TZM alloy prepared by laser cladding. The results showed that the MoSi2-TiVAlZrNb composite coating had a more uniform structure and fewer internal cracks than the single MoSi2 coating. The mass loss of the MoSi2-TiVAlZrNb composite coating was 0.1500–0.8721 g, which was lower than that of the single MoSi2 coating (0.3885–1.14190 g) at 1000 °C–1400 °C for the 1 h oxidation test. The higher oxidation resistance of the MoSi2-TiVAlZrNb composite coating was attributed to the dense oxide film formed by the increase in Ti and Al content on the surface and the decrease in the number of cracks, thus reducing the diffusion of oxygen along the cracks to the matrix. Therefore, the addition of TiVAlZrNb multicomponent alloys could provide a new method for the further development of molybdenum alloys in the field of high-temperature oxidation environments.

Excellent combination of strength and elongation of TZM alloys achieved by c-ZrO2 and single cross rolling

In this study, new TZM-xZrO2 (x = 0, 0.5, 1, 1.5) (wt%) alloys were designed by powder metallurgy solid-solid mixing method combined with single cross rolling. The results show that c-ZrO2 in TZM alloys was mainly spherical, and the average size of c-ZrO2 particle increases gradually from 1.28 μm to 1.71 μm with the increase of its content. c-ZrO2 can effectively refine the molybdenum grain and adsorb the free brittle element O in grain boundaries in the form of TiO2 layer. The interface was composed of three phase: c-ZrO2, Y2O3 and TiO2, with the presence of [0−11] c-ZrO2 ǁ [−11−2] Y2O3 ǁ [−10−3] TiO2 crystal relationship. The rolled plates mainly exist 〈100〉//ND and 〈111〉//ND two kinds of grain orientation, the addition of c-ZrO2 particles promote <100>//ND orientation ratio, thus weakening the texture strength (maximum pole density value from 8.34 to 5.39), conducive to the improvement of plasticity. When the c-ZrO2 content was 0.5 wt%, the best performance was achieved, with good strength and elongation (ultimate tensile strength: 958 MPa; Elongation: 17.3%), showing excellent strength and elongation product (16.6 GPa·%), 31% higher than TZM alloy, better than most reported molybdenum alloys. With the further increase of c-ZrO2 content, the particles gradually coarsened, the hindering effect on dislocations was weakened, and it was easy to become the nucleation site of main cracks, resulting in the decrease of strength and plasticity. Fine grain strengthening and dislocation strengthening were important factors to improve the strength. The excellent ductility was mainly due to the deflection mechanism of microcracks and the blocking effect of grain boundary enrichment on crack propagation.

Effect of Ti and Zr on high temperature mechanical and thermal properties of MoCu composites

Based on the design concept of diversified alloys, the reinforcement of TZM alloys was combined in the fabrication of MoCu composites. The MoCu composites were prepared by vacuum hot press sintering under the effect of Ti, Zr elements added separately or simultaneously, and the microstructure adjustment was realized by mechanical ball milling on the pretreatment of the original alloy powder. The results show that Ti and Zr elements form metal-based solid solutions and intermetallic compounds by diffusion with Mo and Cu matrix during the sintering process. It can not only reduce the sintering activation energy of MoCu composites to improve the densification, but also improve the mechanical properties of the composites through certain solid solution strengthening and second phase strengthening. When Ti, Zr elements are added at the same time, Zr elements can enhance the β-stabilizing effect of Mo on Ti elements and improve the solid solution effect between Ti and Mo, Cu matrix, which further improves the interfacial bonding. Therefore, the 60Mo35Cu2.5Ti2.5Zr composites have the best overall performance, and their thermal properties and mechanical properties at room and high temperatures are greatly improved compared with the original 60Mo40Cu composites.

Data reduction and uncertainty assessment of the direct pulse heating technique with both contact and radiance temperature measurements

This work presents a data reduction procedure of the direct pulse heating technique with both contact and radiance temperature measurements. The technique is applied for the measurement of thermophysical properties of electroconductive solids over a wide temperature range, i.e., from room temperature up to about 2300°C. Absolute and radiance temperatures of a tested material are measured by thermocouple and radiation thermometer, respectively and these and other experimental data are then reduced to the values of specific heat, specific electrical resistivity, hemispherical total emissivity and normal spectral emissivity of the tested material. The related data reduction and corresponding uncertainty assessment for each property is described in detail. An example of uncertainty assessment is given for the recent measurement of specific heat, specific electrical resistivity, hemispherical total emissivity and normal spectral emissivity at 900 nm of molybdenum alloy TZM specimens.

Simultaneous improvement of strength and plasticity of TZM alloys by introducing α-Al2O3 ceramic particles

A new α-Al2O3 ceramic particles reinforced TZM alloy material was prepared by powder metallurgy, exhibiting a better combination of strength and plasticity. Comprehensive tensile tests and detailed microstructure observations showed that compared with the TZM alloy. The ultimate tensile strength and uniform elongation of the TZM-0.9 wt% Al2O3 alloy increased by 22 % and 55 %, respectively, and all the strengthened TZM alloys exhibited typical toughness fracture characteristics. Based on theoretical analysis, strengthening is mainly caused by the mismatch of the elastic modulus between α-Al2O3 ceramic particles and the molybdenum matrix, accounting for 71 % of the increase in total strength. Mismatch of the elastic modulus can increase the dislocation density of the matrix around α-Al2O3 particles. In addition, α-Αl2O3 particles promote the rotation of grains along the <111> direction during plastic deformation, leading to activation of the slip system and promotes the improvement of plasticity.

Oxygen content effect on mechanical properties and microstructure of TZM alloy

A series of molybdenum‑titanium‑zirconium (TZM) alloys with continuous oxygen content gradients were fabricated by powder metallurgy and the correlation between microstructure and properties was investigated. By controlling the carbon source, TZM-like alloys with an oxygen content of 2000 ppm, 1000 ppm, and TZM alloy with an oxygen content of 300 ppm (±100) were obtained, followed by rolling and heat treatment, and the effect of oxygen on the development of the microstructure and the mechanical properties of the alloy was studied. The results show that the changing of the oxygen content has a significant impact on the mechanical properties and microstructure of the alloy. With the increase in oxygen content, titanium and zirconium are more inclined to combine with oxygen to form oxide particles of titanium and zirconium (TiO2, ZrO2), the secondary phase particles increase significantly, and the alloy strengthening mode changes from solid solution strengthening to secondary phase dispersion strengthening. Owing to the inhibition of grain boundary migration by the secondary phase, the grain size of the alloy decreases as its oxygen content rises, which causes an increase in hardness of around 10 HV0.1 for every 1000 ppm increase in oxygen content. According to the Hall-Petch relationship, the yield strength of the annealed alloy increased from 336 MPa (300 ppm) to 556 MPa (2000 ppm) with smaller grain size. Kernal Average Misorientation (KAM) is used to characterize the dislocation density of the alloy, and the results show that the value of KAM is negatively correlated with the toughness of the alloy. The KAM value of the alloy is the lowest at 1000 ppm and its greatest elongation reaching 16.8%. Dislocation cells formed in the long-striped grains with an oxygen content of 300 ppm, greatly enhancing the strength of the material and maintain good plasticity. TZM alloy with 300 ppm oxygen has the highest tensile strength of 866 MPa and has an elongation of 15%, which is the leading performance compared with ASTM-specification B386/B386M.

Deformation behavior and microstructure evolution of TZM alloy with 1.0 wt%ZrO2 under high temperature compression

The hot deformation behavior of TZM-1.0 wt% ZrO2 alloy in the temperature range of 1000–1600 °C and strain rate range of 0.005–1 s−1 was studied by hot compression method. The constitutive equation and hot working diagram were established, and the microstructure evolution was emphatically analyzed by SEM and EBSD. The results indicate that the flow stress decreases with the increase of temperature and the decrease of strain rate, and ZrO2 particles can improve the stability of TZM alloy in rate-control during hot deformation. The constitutive equation accurately predicted the correlation coefficient as high as 0.9685, calculated the average activation energy Q = 426 kJ mol−1, and obtained the best process parameters of 1150 °C–1250 °C /0.01–0.05 s−1 under 0.7 strain. The unstable zone was mainly composed of a small number of coarse grains and a large number of fine grains. The main reason for flow instability was the disharmonious deformation between coarse and fine grains during compression. The optimum hot working zone consists of more uniform equiaxed grains. However, EBSD observed that at a strain rate of 1 s−1, the recrystallization fraction at 1600 °C was lower than 1200 °C, and the dynamic recrystallization (DRX) and texture evolution trends at 1200 °C and 1600 °C were completely different. The abnormal changes in recrystallization fraction and texture evolution at 1600 °C were due to the competition between deformed grain growth and DRX on energy storage consumption, and the effect of deformed grain growth on energy storage consumption was greater than that of DRX. At 1600 °C/1 s−1, the growth of deformed grains was dominant, exhibiting strong texture components in the [001] direction, with〈100〉fibers as the main component and the highest peak texture strength. As the strain rate decreases, DRX dominates and weakens the texture strength, resulting in a significant decrease in<100>fibers.

Fabrication and Oxidation Resistance of a Novel MoSi2-ZrB2-Based Coating on Mo-Based Alloy.

To enhance the oxidation resistance of Mo-based TZM alloy (Mo-0.5Ti-0.1Zr-0.02C, wt%), a novel MoSi2-ZrB2 composite coating was applied on the TZM substrate by a two-step process comprising the in situ reaction of Mo, Zr, and B4C to form a ZrB2-MoB pre-layer followed by pack siliconizing. The as-packed coating was composed of a multi-layer structure, consisting of a MoB diffusion layer, an MoSi2-ZrB2 inner layer, and an outer layer of mixture of MoSi2 and Al2O3. The composite coating could provide excellent oxidation-resistant protection for the TZM alloy at 1600 °C. The oxidation kinetic curve of the composite coating followed the parabolic rule, and the weight gain of the coated sample after 20 h of oxidation at 1600 °C was only 5.24 mg/cm2. During oxidation, a dense and continuous SiO2-baed oxide scale embedded with ZrO2 and ZrSiO4 particles showing high thermal stability and low oxygen permeability could be formed on the surface of the coating by oxidation of MoSi2 and ZrB2, which could hinder the inward diffusion of oxygen at high temperatures. Concurrently, the MoB inner diffusion layer played an important role in hindering the diffusion of Si inward with regard to the TZM alloy and could retard the degradation of MoSi2, which could also improve the long life of the coating.

Evaluation of tensile property and strengthening mechanism of Zirconia reinforced molybdenum alloy

In this experiment, the nano-ZrO2 particles reinforced molybdenum alloy with excellent mechanical properties were prepared through liquid-liquid doping process, and the comparison with TZM alloy prepared by solid-solid doping process was conducted. During the liquid-liquid doping process, the ZrO2 particles ensured the dispersion of the second phase in alloy because they reached molecular-level uniformity, and the hydrothermal synthesis preparation process enabled the ZrO2 particles in alloy to reach nanometer size level. In Mo-ZrO2 alloy, the small and dispersed ZrO2 can effectively block dislocation and passivation cracks; both the room temperature and high temperature performance of Mo-1.5 %ZrO2 alloy was better than that of TZM alloy. Based on the hindered recrystallization process, improved recrystallization temperature, as well as enhanced recrystallization strength thanks to the alloy pinning effect of ZrO2, the maximum tensile stress of Mo-1.5 %ZrO2 alloy at 1000 ℃ was about 14 % higher than pure molybdenum, and the maximum tensile stress of Mo-1.5 %ZrO2 alloy at 1400 ℃ was at least 45 % higher than pure molybdenum. Quantitative analysis shows that the strengthening effect of the second phase was the best during the recrystallization process.

Vacuum brazing of TZM alloy and graphite with Ti-35Ni alloy: Microstructure, properties, and mechanism

In the present work, a reliable TZM/graphite heterogeneous joint was prepared by vacuum brazing with Ti-35Ni alloy. The influence of brazing temperature on the interfacial microstructure, shear strength, and fracture characteristics of the joints were analyzed. The formation mechanism of the joints was also investigated in detail. TiC layer was formed on graphite during the vacuum brazing process, characterized by SEM and TEM analysis. The interfacial microstructure of the joints brazed at 1200 °C was TZM/Ti(s,s)/TiNi + Ti2Ni/TiC/graphite. The thickness of TiC layer gradually increased with the increase in brazing temperature. In addition, the shear strength of TZM/graphite heterogeneous joints increased first and then decreased, reaching the peak value of 14.5 MPa at 1300 °C. Under optimal vacuum brazing temperature, the fracture path of the joint started in the TiC layer and then extended to the interior of the graphite substrate.

Molybdenum alloy Mo-Ti-Zr-C adapted for laser powder bed fusion with refined isotropic microstructure and excellent high temperature strength

The molybdenum‑titanium‑zirconium‑carbon alloy TZM is one of the few molybdenum alloys that can be processed crack-free in laser powder bed fusion (LPBF). However, the parts have a coarse-grained, columnar microstructure comprising epitaxially grown grains, and their strength is limited by residual porosity. Consequently, the mechanical properties do not reach the values of their conventionally powder-metallurgically produced pendants. In this work, the conventional alloy composition of TZM was adapted to the unique processing conditions in laser powder bed fusion by increasing the carbon content, and the effects on the microstructure and mechanical properties were investigated.Increasing the carbon content to 2.3 at.% yielded a significantly refined and isotropic microstructure. In addition, C led to the formation of a cellular subgrain structure consisting of (Mo, Ti) cells 0.4 ± 0.1 μm in size surrounded by a closed network of ternary (Mo, Ti) carbide. Residual oxygen impurities in C-modified TZM were partly dissolved in the ternary (Mo, Ti) carbide network and partly bound by Zr as nanometer-sized ZrO2 particles. These two mechanisms for binding oxygen minimized oxygen segregation—a major issue limiting the grain boundary strength in Mo and Mo alloys—and thus purified and strengthened the grain boundaries. The mechanical strength increase due to the increase in carbon content was 50% (0.5 at.% C vs 2.3 at.% C). At elevated test temperatures of 800 °C and 1200 °C, TZM-2.3 at.% C exceeded the ultimate tensile strength (UTS) of conventionally produced TZM by 24% and 16%, respectively.

Brazing SiCf/SiC and TZM alloy with AuPdTiCrCu dual active element filler metal

AbstractFor the joining of SiCf/SiC and TZM alloy, an AuPdTiCrCu filler metal with dual active element of Ti and Cr was synthesized. The brazing process was carried out under the condition of 1200°C for 10 min. It was shown that fine Cr‐based solid solutions were dispersed in the filler metal. When brazing, the element Cr and Ti moved toward the base metal and reacted with them to form into Mo‐Cr‐Si and Mo‐Cr‐Ti‐Si compounds. These two active elements could promote the metallurgical reaction of the joint. Meanwhile, it was found that some Pd‐Si compounds, fragments of (Au, Cu)ss and soft Au‐Ti phases formed in the middle regions of the joint. (Au, Cu)ss and Au‐Ti phases distributed around the Pd‐Si compounds. In addition, the joining mechanism was discussed and the mechanical properties of the joints were tested. The results showed that the average four point flexural strength of the joints reached 88.5 MPa at room temperature and 46.8 MPa at 500°C. The fracture characters of the joints were discussed in the last.