Alloy Joints Research Articles

Effect of double-pulse frequency and post-weld heat treatment on microstructure and mechanical properties of metal-inert gas welded Al–Mg–Si alloy joints

The Al–Mg–Si alloy welded structure is widely used in aerospace, marine ship, automotive and other industries. However, the mechanical properties of welded joint were seriously weakened due to the microstructure coarsening and heat affected zone (HAZ) softening, making its service life decayed. In this paper, in order to enhance the mechanical properties of Al–Mg–Si alloy welded joint, a coupled method including double pulsed Metal Inert Gas (DP-MIG) welding technology and post-weld heat treatment (PWHT) were applied on the joining process of Al–Mg–Si alloy. With the increase of DP frequency from 2 Hz to 5 Hz, the average grain size of fusion zone decreased from 113.7 μm to 88.4 μm. And the tensile strength of welded joint was at the interval of 180∼190 MPa. After a suitable heat treatment (solution treatment at 530 °C for 2 h and aging treatment at 180 °C for 8 h), the tensile strength of welded joint increased to 318.3–333.8 MPa, which exceeds 90 % of the base metal (BM). Under the comprehensive effect of solid solution strengthening, fine grain strengthening, and precipitation strengthening, the mechanical properties of Al–Mg–Si alloy welded joint were significantly improved. And the research results in this paper can provide a research basis for high quality connection of Al–Mg–Si alloys.

Investigation on the room temperature compressive creep behavior of TC4 titanium alloy joints with vacuum electron beam welding

The room temperature compressive creep behavior is a key issue for the titanium alloys welded structural components served in deep-sea environment. In the present work, the compressive creep behavior of different areas for TC4 titanium alloy joints with vacuum electron beam welding was systematically studied, and it is found that the fusion zone (FZ) of TC4 titanium alloy joints has the minimum creep strain rate. This is mainly because the creep deformation of TC4 titanium alloy is mainly controlled by the movement of dislocations in the α or α′ phases, the size of α′ phase in FZ is small, and thus the dislocation slip is limited. MD simulation results have further revealed that the room temperature compressive creep nature of α-Ti can be regarded as a dynamic hysteresis phenomenon in plastic strain and is dominated by the dislocation movement.

Numerical simulation and properties analysis of Ta10W alloy joints prepared by electron beam welding

Vacuum electron beam welding has the characteristics of concentrated energy, controllable heat input, almost no pollution, and a small heat-affected zone. In this study, the Ta10W alloy was successfully connected by electron beam welding (EBW), and numerical simulations were employed to examine the distribution of temperature and stress fields throughout the welding process. Additionally, the influence of EBW on the microstructure and corrosion resistance of the welded joints was scrutinized. Findings indicate that the welding heat process led to a reduction in grain boundary energy, thereby facilitating thermal activation processes that contributed to grain growth. Grain boundary migration and possible dynamic crystallization led to the appearance of the coarse columnar crystal structure in the welded joint. A three-dimensional, nonlinear, transient, thermo-mechanically coupled finite element model was developed for the electron beam welding of Ta10W alloy. The shape characteristics and size of the weld and transient thermal cycles calculated by numerical simulations were in reasonable agreement with experimental results. Electron beam welding reduced the corrosion resistance of the Ta10W alloy, and the corrosion product was mainly composed of Ta, O and Na.

Interfacial structure and properties of anodized 6061 Al alloy joints by ultrasonic-assisted hot dipping and soldering using a Sn–9Zn–2Al filler metal

Al alloy joints soldered with Sn-based filler metal are susceptible to corrosion and early failure when exposed to moisture, resulting in severe accidents and substantial economic losses. This study proposes a method to prevent galvanic corrosion by separating Al alloys and Sn-based filler metals with an insulating barrier layer of anodized aluminum oxide (AAO) composed of Al2O3. The successful joining of anodized aluminum alloy (AAA) with Sn–9Zn–2Al was achieved through ultrasonic-assisted hot dipping and soldering in air at 240 °C. Microstructural examination revealed strong bonding between the solder alloy and AAO, with the solder infiltrating the AAO nanotubes and a transition layer consisting of two sublayers at the interface: amorphous ZnO mixed with nanocrystals (ZnO and Al2O3) and amorphous Al2O3. The shear strength of the joints ranged from 31.8 to 32.8 MPa when subjected to ultrasonic hot dipping for 0.5–2.0 s, with no significant difference observed. Fracture initiation and propagation occur within the transition layer at the interface. The shear strength of joints subjected to dipping for more than 3.0 s decreased slightly to 27.9 MPa due to localized peeling off of AAO from the Al substrate. The formation of the interface involves the segregation of Al and Zn on the liquid filler metal surface, driven by differences in atomic activity. Due to the jet force from cavitation, an Al-rich liquid infiltrates the nanotube, resulting in the formation of Zn–O at the interface and Al–O both at the interface and within the nanotube. Throughout this process, the wetting model shifts from a Cassie state to a near-Wenzel state. Immersion tests of two types of joints, Al/SnZnAl/Al and AAA/SnZnAl/AAA, confirmed that galvanic corrosion of Sn/Al was completely inhibited by the latter. Consequently, AAA joints demonstrate excellent corrosion resistance, validating this approach as a promising solution to the Al/Sn galvanic corrosion issue.

Ultra-strong bonding of 30-wt% GF/PET-A2024 aluminium alloy via collaborative promotion of ultrasonic-assisted FeCl3+N2H4 corrosion and the coordination bonds by Zr4+

Enhancing the bonding strength between metals and polymers is advantageous for hybrid structures used in aerospace and power electronics applications. This study, conducted for the first time, involves the preparation of multi-scale “honeycomb-meteorite crater” morphologies on the surface of A2024 aluminium alloy through a multi-step ultrasonic-assisted corrosion treatment. The ultrasonic-assisted FeCl3/N2H4 corrosion process increased the interfacial tensile shear strength of a 30-wt% glass fibre reinforced PET-A2024 aluminium alloy joint (expressed as 30-wt% GF/PET-A2024) to 32.0 MPa. Coating Zr4+ substantially enhances the hydrophilicity of the A2024 surface; however, the coordination bonding effect of Zr4+ can only be activated after prolonged heat treatment (100 °C, 3 h). With the combined effects of multi-scale mechanical interlocking and coordination bonding of Zr4+, the tensile shear strength of the 30-wt% GF/PET-A2024 joint can reach 56.5 MPa, surpassing existing works by a significant margin. Experimental results and Density Functional Theory (DFT) calculations demonstrate that the optimal concentration for Zr4+ treatment is 1.5 wt%. Excessive Zr4+ would lead to ion-dipole interactions, which diminish the interface bonding strength; when the concentration of Zr4+ is 2 wt%, The joint strength dropped sharply to 39.1 MPa. This study provides a comprehensive discussion on ultrasonic-assisted corrosion and the effect of Zr4+, offering valuable insights for future research aimed at enhancing the interfacial bonding strength between polymers and metals.

Increased tensile strength induced by the precipitation of nanocrystals for welding joints of Zr-based amorphous alloys

Zr-based amorphous alloys have attracted intensive attention for applications because of their excellent mechanical property. However, the welding process is inevitable for some special cases, such as the obtain of large size structure parts. It is significant to clarify the influence of introduced welding joints on mechanical properties in Zr-based amorphous alloys. Herein, the increased tensile strength of welding joints in Zr-based amorphous alloys is demonstrated by choosing a suitable initial temperature of Cu cooling fixtures for pulsed laser welding. It is found that an optimized tensile strength is observed when the initial temperature is −20 °C. With the decrease of the initial temperature from 10 to −30 °C, the tensile strength shows a trend of first increasing and then decreasing. Combined with the characterization of microstructures, it can be concluded that the increased tensile strength results from the precipitation of nanocrystals in the heat affected zone. Thus, our results provide a method to improve the mechanical property by controlling the microstructures of the heat affected zone in welding joints of Zr-based amorphous alloys.

Microstructure and properties of SLMed Ta-10W and rolled Ta-10W fiber laser welded joint

This study focused on the mechanical properties and microstructure of fiber laser-welded joints of Ta-10W alloy manufactured by selective laser melting (SLM) and rolled. In the SLMed base material side of the weld, columnar grains were formed along the weld, extending up to half of the weld width. The base material’s anisotropy influenced the subgrain morphology, and grain orientation changed after welding. When the building direction of the SLMed Ta-10W was perpendicular to the welding direction, slender columnar subgrains were prone to forming in the SLM side weld. In contrast, when the building direction was parallel to the welding direction, equiaxed subgrains tended to form in the weld. In the rolling base material side weld, mainly equiaxed grains were formed, with subgrain morphology and orientation randomly distributed. In the weld center, fine-grain zones of 10–20 μm, comprising fine grains of 2–5 μm diameter, were observed in all welds under study. Room-temperature tensile strengths of both welds were approximately 620 MPa, falling between the strengths of the two base materials. Their fracture surfaces displayed a mixed mode of cleavage and intergranular fracture. High-temperature strengths of rolled-SLMed joints varied with SLM directions X and Z, reaching 124.94 and 107.87 MPa, respectively, and exhibiting similar fracture characteristics dominated by intergranular fracture.

The Effects of Combined Treatments of Laser Engraving, Plasma Spraying and Resin Pre-Coating on Improving the Bonding Strength of Titanium Alloy and Carbon Fiber-Reinforced Polymer.

This study focused on effective methods of laser engraving treatment (LET), plasma spraying, and resin pre-coating (RPC) to manufacture the reinforced adhesive joints of titanium alloy and carbon fiber-reinforced polymer (TA-CFRP) composites. The combined treatments contributed to the creation of a better adhesive bonding condition and offer a vertical gap between circular protrusions to form epoxy pins and carbon nanotube (CNT)-reinforced epoxy pins. The bonding strength of the TA-CFRP composite was reinforced by 130.6% via treatments with a twice-engraving unit of 0.8 mm, plasma spraying, and RPC. The original debonding failure on the TA surface was changed into the cohesive failure of the epoxy adhesive and delamination-dominated failure of the CFRP panel. Overall, laser engraving has been confirmed as an effective and controllable treatment method to reinforce the bonding strength of the TA-CFRP joint combined with plasma spraying and RPC. It may be considered as an alternative in industry for manufacturing high-performance metal-CFRP composites.

Effects of recrystallization on interfacial microstructure evolution and shear strength of TiAl alloy joints

The effects of dynamic recrystallization (DRX) and post-bonding heat treatment (PBHT) on the interfacial microstructure evolution and mechanical properties enhancement of Ti-43Al-4Nb-1Mo-0.2B alloy joints, subjected to various bonding parameters, were thoroughly investigated through detailed microstructural characterization and shear performance tests. A strip-like DRX area was observed at the interface when bonding at 1100 °C, ≥30 MPa, for 60 min. Equiaxial- γ grains underwent discontinuous dynamic recrystallization during the bonding process, and tended to form flat grains parallel to the lamellae direction during recrystallization annealing (1000 °C/6 h) owing to the hindrance imposed by the lamellae on both sides. The orientations of lamellae on the both sides of bonding interface affects the lamellae's stress distribution and deformation behavior at the bonding interface, subsequently influencing the DRX behavior and the width of the DRX zone. Static recrystallization (SRX) during the recrystallization annealing treatment can eliminate bonding defects of joints bonding at lower pressures or temperatures. Optimal joints with fully lamellar interfacial microstructure and excellent shear properties can be obtained through single-α phase annealing treatment. Lamellae microstructure tailored through PBHT can significantly enhance the quality of joints, attributed to the homogeneity of the microstructure between the interface and matrix. The highest shear strength of 478 MPa, accounting for 82 % of the matrix strength, was obtained under the bonding parameters of 1100 °C/30 MPa/60 min-1290 °C/15 min. This work provides important DB process parameters for fabricating of complex structural parts of TiAl alloy.

Microstructure formation mechanism and mechanical properties of super-thickness TC11 titanium alloy joint by electron beam welding and laser additive manufacturing hybrid connection technology

Advanced connection technology for extra-large/super-thickness titanium wrought components is urgent demand in aerospace manufacturing industries. For achieving high-performance titanium alloy super-thickness joint with a high connecting efficiency, a novelty concept of hybrid connection technology with electron-beam welding and subsequent laser additive connection is proposed. A super-thickness (200 mm) TC11 titanium alloy joint has been successfully prepared, and microstructure, tensile properties and fracture behavior of different regions in which are investigated. The results suggest that in stress-relieve heat treatment (SRT) condition, deformation and fracture of the joint are prone to occur in its low-strength wrought base material zone; after double annealing heat treatment (DAT), lamellar α phases in different zones of the joint become similar, associating with a higher fraction of fine secondary α phases in wrought base material zone. Therefore, the tensile properties of the joint are comparable to wrought properties. Although strength in different zones of hybrid connection joint is similar, ductility is not uniform and apparently lower in middle fusion zone due to grain heterogeneity. Overall, these findings indicate that hybrid connection can be one potential technology for fabricating high performance super-thickness titanium alloy joint with a high connection efficiency in engineering application fields.

Development of large-size dissimilar stainless steel/α-Ti alloy joints by diffusion bonding using vacuum hot press: Interface microstructure and tensile response in the temperature range of 77–773 K

In the present study, dissimilar metal joints of SS321 and Ti–5Al-2.5Sn (α-Ti alloy) are produced by diffusion bonding at temperatures of 850, 900, and 950 °C under 10 MPa pressure for 30 min duration using a vacuum hot press (VHP). The interface of the joints was characterized through scanning electron microscopy coupled with energy dispersive spectroscopy and electron backscattered diffraction analysis for examining microstructure, morphology, and microchemistry across the interface. The effect of change in the heating process during diffusion bonding on the growth kinetics of interface layers was investigated. The interface of the joints comprised of intermetallic phases of σ phase, χ phase, (Fe,Cr)2Ti, FeTi and β-Ti. The joint produced at 900 °C has exhibited a maximum tensile strength of 315 MPa, 253 MPa, and 208 MPa at the test temperatures of −196 °C (77 K), room temperature (300 K), and 500 °C (773 K), respectively. Reduction in joint strength was noticed at test temperatures of RT and −196 °C for the samples bonded at a higher temperature of 950 °C due to the increased widths of the intermetallic phases at the interface. The effect of the bonding temperature on the tensile strength of the joints at an elevated test temperature of 500 °C was found to be negligible; however, the joints displayed good retention of strength along with substantial strain hardening followed by ductility at 500 °C. Fracture surfaces of RT and −196 °C tested samples showed the mixed mode of featureless smooth and cleavage fracture, whereas the 500 °C tested sample displayed planar interface failure. The zone of failure of the joints was noted to be around the interphase layer made of (Fe,Cr)2Ti + FeTi intermetallics.

Strength-ductility synergy of a laser welded 7085Al matrix nanocomposite joint: Interaction between ZrB2, Al3(Er, Zr) nanoparticles and MgZn2 precipitates

The dissolution and coarsening of precipitates during welding thermal cycle weakened mechanical properties of 7xxx Al alloy joints. In this work, ZrB2 ceramic nanoparticles and core-shell structured Al3(Er, Zr) (L12) with high thermal stability were introduced to synergistically enhance the mechanical property of laser welded 7085Al nanocomposite joint, and the interaction between ZrB2, Al3(Er, Zr) nanoparticles and MgZn2 precipitates was analyzed. The results showed that grain boundaries were covered by fine precipitates with discrete distribution under the action of ZrB2 and Al3(Er, Zr). The interface coherency of ZrB2/Al and Al3(Er, Zr)/Al was improved by introducing highly coherent MgZn2 precipitates to form coherent multi-interfaces of ZrB2/MgZn2/Al and Al3(Er, Zr)/MgZn2/Al. The ultimate tensile strength and uniform elongation of ZrB2/7085Al-Er nanocomposite joint were 678.9 MPa and 18.5 %, with a 36.6 % and 55.5 % increase as compared to 7085Al counterpart. The reinforced grain boundary can prevent strain localization here and allow the activation of high density of dislocations within grains. The higher interface coherency could effectively promote the dislocation multiplication and dislocation annihilation, relieving stress concentration at semi-coherent interface caused by dislocation pile-up. Finally, the strength-ductility synergy was achieved in ZrB2/7085Al-Er nanocomposite joint by strengthening grain boundary and tailoring interface structure.

RETRACTED ARTICLE: Investigating the strength of butt-welded joints of AA6082 and AA5052 alloys through friction stir welding; the impact of tool tilt angle and feed rate

We, the Editors and Publisher of the Journal of Adhesion Science and Technology, have retracted the following article: Investigating the strength of butt-welded joints of AA6082 and AA5052 alloys through friction stir welding; the impact of tool tilt angle and feed rate. Journal of Adhesion Science and Technology, https://doi.org/10.1080/01694243.2023.2253631. Bhiksha Gugulothua, Rajasekaran Saminathan, A. Pradeep, Ankit Sharma, S. Vijayakumar, Prabhu Paramasivam, and N. Srinivasa Rao. (2023). Since publication, concerns have been raised by a third party about the integrity of the data presented in the article, as well as potential authorship concerns. When approached for an explanation, the authors have been unable to provide their original data to verify its authenticity. In addition, the authors have not fully responded to our questions regarding the process of the research conducted. We have been informed in our decision-making by editorial policies and the COPE guidelines. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Numerical simulation and experimental investigation on friction stir welding of AZ31 magnesium alloy

Integrated numerical simulations and experimental investigations were employed to scrutinize the thermal, mechanical, and microstructural transformations of the AZ31 magnesium alloy during the friction stir welding (FSW) process. Especially, the primary focus was on the influence of process parameters such as rotational speed and welding speed on the temperature distribution, grain refinement, and mechanical properties of welded joints in alloys. By employing Deform-3D coupled with the integration of constitutive equations and dynamic recrystallization (DRX) models, the FSW process was investigated. The investigation revealed a significant increase in temperature when the tool’s shoulder made contact with the weld, resulting in the substantial accumulation of heat during FSW. Distinctions became apparent between the advancing side (AS) and the receding side (RS), with the AS exhibiting slightly elevated levels of temperature, equivalent stress, strain, and grain size. Specifically, adjustments in the rotational speed of the stirring tool and a reduction in welding speed resulted in larger grain sizes within the alloy. For example, when the rotational speed was set at 1200 rpm and the travel rate was 200 mm min−1, the initial grain size of the weld experienced a substantial decrease from 57.8 μm to 8.2 μm. Subsequent experimental verification, considering grain size and microhardness, was carried out to optimize FSW parameters for achieving the desired material properties. The accuracy of simulation results was validated through a meticulous comparison with experimental findings, underscoring the potential of numerical simulation in comprehending and predicting FSW processes.

Ultrasonic-Assisted Tungsten Inert Gas Welding of Inconel 625 Joints to Reduce Hot Cracking and Improve Microhardness: Optimization and Prediction Methods

Abstract This research article investigated the optimized process parameters for decreasing the hot cracking phenomenon and improving the microhardness of ultrasonic vibratory-assisted tungsten inert gas (U-TIG) welding of Inconel 625 alloy. The study employed two approaches: response surface methodology (RSM) and RSM coupled with a genetic algorithm (RSM-GA). The objective was to analyze the impact of welding process parameters, including welding current, gas flow rate, presence or absence of ultrasonic vibration, and filler material, on the crack length and microhardness of the welded joints. Experimental tests were conducted using RSM with a full factorial central composite design matrix, enabling comprehensive parameter space exploration. Parametric mathematical models were developed based on the obtained experimental data. These models were then utilized as fitness functions within the GA to determine the global optimal solution, aiming to minimize crack length and maximize microhardness. Additionally, artificial neural network (ANN) models were developed to predict the responses and optimize the welding process. The comparison between the experimental and predicted data demonstrated the reliability of the ANN model in accurately estimating the crack length and microhardness of U-TIG welded Inconel 625 alloy joints. The developed models achieved a prediction accuracy of less than 5 % error.

Mechanical properties and corrosion resistance of TC4 titanium alloy joints by plasma arc welding + gas tungsten arc welding combination welding

Mechanical properties and corrosion resistance of TC4 titanium alloy joints by plasma arc welding + gas tungsten arc welding combination welding

Structure and mechanical properties of Ti2AlNb-based alloy welded joints using keyhole plasma arc welding with subsequent heat treatment

Using keyhole plasma arc welding, welded joints of a Ti2AlNb-based alloy, VTI-4, were obtained, and their structure and mechanical properties were studied. It has been established that the dynamic effect of a keyhole arc had a positive effect on the quality of the welded joint; namely, lack of penetration, porosity, and microcracks were eliminated. The welded joint consisted of a fusion zone (FZ), a heat-affected zone (HAZ), and a base metal (BM). Depending on the phase composition and morphology of the obtained phases, the HAZ can be divided into four zones: HAZ1 with large β-phase grains near the melting line, HAZ2 with large β-phase grains + α2, HAZ3 with more fragmented β-phase grains retaining more α2-phase, and HAZ4 with the phase composition β + α2 + O. Subsequent heat treatment (HT: quenching at 920 °C for 2 h, cooling in air, followed by aging at 800 °C for 6 h, cooling in air) preserved the zone structure of the weld but led to the formation of the O-phase within β-grains. The microhardness of the weld in the zone corresponds to 360±15 HV0.2, but after HT, it increased to 382±20 HV0.2. The strength properties of the welded joint after HT were above 90 % of the base metal (σucs = 1120 MPa, σ0.2 = 1090 MPa), while elongation to failure is close to the initial condition (δ = 2.1 %).

Fatigue crack evaluation of butt weld joints in full-scale aluminum alloy joints: Experimental and numerical study of traction structural stress

In this study, the digital image correlation technique is used to determine the inconsistent mechanical properties and microstructure non-uniformity in different regions of aluminum alloy butt welded joints. A state monitoring method is proposed based on phased-array ultrasonic total focus imaging for crack evolution. A series of surface fatigue crack propagation tests on full-scale aluminum alloy butt welds are investigated, which innovatively revealed the mechanism and evolution law of crack propagation at the surface of the weld. The analytical function for dynamic crack propagation in welded structures is proposed, which provides a new idea and data support for clarifying the state deterioration process of structures. The results show that the traction structural stress can effectively identify the critical fatigue position of the weld and effectively account for the effect of angular misalignment. The phased-array ultrasonic total-focus imaging monitoring analysis method for surface fatigue crack propagation is proposed to improve the completeness of the fatigue crack evolution law.

Microstructure and strengthening mechanism of TIG welded joint of AZ31 alloy based on FSP technique

Magnesium alloys, renowned for their outstanding properties, present promising applications within the realm of advanced manufacturing. Addressing the challenges of coarse grains and inferior properties in the fusion welding of magnesium alloys, a novel strengthening approach for fusion-welded joints is proposed in this study. This method employs fine, uniform, and dense grains as the matrix, with particle-reinforced structures serving as the strengthening backbone. By utilizing powder feeding in conjunction with fusion welding and friction stir processing, ideal microstructures were successfully fabricated, and the mechanisms influencing grain morphology and joint properties were explored. Following the strengthening treatment, the grain size of the magnesium alloy molten weld was reduced from 193.5 μm to 15.9 μm, resulting in a grain refinement efficacy of 91.8 %. Concurrently, the tensile strength was augmented by 70.2 MPa, and the elongation experienced a 136 % enhancement. The grain morphology, eutectic phase structure, texture strength, precipitated phase type and dislocation distribution at each processing stage of the welded joint were observed. Research shows that nano-enhanced particles adhere to the eutectic structure of grain boundaries, effectively inhibiting the diffusion of solute elements and significantly reducing the dendrite growth rate. It is the main mechanism by which reinforced particles lead to grain refinement. Discontinuous recrystallization during FSP treatment leads to grain refinement, work hardening and enhanced pinning of particles at grain boundaries, which are the main reasons for the strength improvement.

Microstructure evolution and crack prevention in TiC nanoparticles-enhanced 2195 Al[sbnd]Li alloy joint fabricated by coaxial fiber-diode hybrid laser wire-feeding welding

High hot crack susceptibility (HCS) in laser-welded 2195 AlLi alloy poses a considerable challenge that restricts its widespread application. Nonetheless, the utilization of advanced laser beam shaping technology and nano-technology presents novel approaches to modify the melting and solidification procedures, enabling precise control over microstructure and crack. Herein, a crack-free and well-formed weld seam (WS) of 2195 AlLi alloy was successfully achieved by employing a coaxial “Gussies + Flat top” hybrid laser source and introducing TiC nanoparticles. The contrast experiments were performed to comprehensively investigate the effect of TiC nanoparticles on the microstructure evolution and hot cracks in welded joints of 2195 AlLi alloy. The results indicated that the crack propagation occurs linearly along the grain boundaries of columnar dendrites and laterally along the grain boundaries of equiaxed dendrite utilizing the conventional AlCu filling wire. With the assistance of TiC nanoparticles, the crack-free WS with homogeneously equiaxed dendrites is facilitated. The elimination of cracks by introducing TiC nanoparticles is attributed to the ameliorative liquid feeding channels, grain refinement, as well as the the pinning effect of TiC nanoparticles.