Fine Grain Research Articles

Developing high strength and ductility in cobalt alloy via chromium carbonitride addition

In this study, we present a strategy for the development of cobalt alloy with high performance, by introducing a nitrogen-containing solid solution powder Cr2(C,N). Despite the cobalt accelerates the nitrogen removal from Cr2(C,N) during sintering, interestingly, nitrogen seemingly plays a pivotal role in regulating the microstructure of cobalt alloy. Detailed microstructural analyses indicate that the fcc-Co increase, CrN precipitates and finer grain size are formed within the cobalt matrix with Cr2(C,N) addition. These structural modifications significantly contribute to the strength and toughness. In comparison to the without N-doped cobalt alloy, the compressive strength undergoes a significant 34% increase, rising from 1150 MPa to 1540 MPa. Similarly, the bending strength exhibits an upward trend, ascending from 1605 MPa to 1766 MPa. Concurrently, the introduction of Cr2(C,N) results in an almost 80% enhancement in bending strain compared to the without N-doped one. Additionally, a notable 28% increase in hardness is obtained. The substantial enhancements in strength and toughness are mainly attributed to the combined effects of solid solution and precipitation strengthening. Our findings confirm the capability of Cr2(C,N) to the cobalt alloy reinforcement, providing valuable insights for integrating Cr2(C,N) to enhance the cobalt alloy, and laying a foundation for future investigations into the forms of nitrogen and the strengthening and toughening mechanisms of nitrogen-containing alloy. The insights gained in this study also provide novel strategies for the design of materials characterized by both needed strength and ductility, thereby advancing the development of ultra-strong and ductile materials with superior toughness.

Microstructure evolution and property of high manganese steel coatings by laser shock assisted laser wire cladding

Field-assisted laser cladding (FALC) overcomes the limitations of laser cladding through the inherent advantages brought about by the use of various auxiliary energy fields (AEFs). Laser wire cladding (LWC) is limited by the common problems of laser cladding but has a promising future due to the extremely high material utilization rate. In this study, a laser shock assisted laser wire cladding (LSALWC) manufacturing process was proposed. In situ laser shock was introduced into the LWC to obtain finer grains structure and improve product performance. LSALWC does not change the composition of the coating, does not require the use of pretreatment and post-treatment, and does not reduce the efficiency of production. Using high manganese steel (HMS) as the model alloy, LSALWC was employed to achieve the expectation of reducing the proportion of columnar grains, refine the microstructure of columnar grains, and transform columnar grains into equiaxed grains. Compared with the sample (LC) manufactured by LWC, the performance of the sample (LSA) manufactured by LSALWC has been improved, the hardness increased from 285 ± 5 HV0.5 to 303 ± 6 HV0.5, the volume wear rate decreased from 2.1 × 10−4 mm3/N·m to 1.7 × 10−4 mm3/N·m, the primary dendrite spacing of the coating was reduced by 11.5%, and the heterogeneity of coating was more obvious. The cladding process under laser shock was studied using a high-speed camera, and the influence of laser shock on the coating was explained. The mechanism of the performance improvement of the LSA sample was explained. This study showed the disturbance of the molten pool was enhanced by laser shock, and the dendrites at the bottom were deflected or even broken. The broken dendrites were dispersed with the liquid flow and became new nucleation sites. Laser shock increased the supercooling during solidification by reducing the temperature gradient in the molten pool, and created an environment conducive to grain nucleation and growth. This process mitigates various issues in the casting process of HMS and provides a novel method for regulating the grain and microstructure of laser cladding. This research delves into the coupling between the AEF and the dynamic behavior of the molten pool, culminating in a model depicting the evolution of laser cladding solidification under the influence of the AEF, which will provide a new perspective for the research of FALC.

On the fabrication of finer grain structure through using finer wire diameter for wire arc additive manufacturing of AZ31B magnesium alloy

Magnesium (Mg) alloys are the lightest structural metallic material, but it is hard to be applied to various industrial fields due to the crystallographic nature that is composed with hexagonal closed packed (HCP). Wire arc additive manufacturing (WAAM) could be a key to fabricating Mg parts with large sizes and complex designs. It has numerous advantages such as high material efficiency, short-delivery time by faster manufacturing speed, easy to modify, etc. Yet, most of the research mentioned the grain coarsening and degradation in mechanical properties when fabricating WAAM products using Mg alloy wires. To solve the problems, a solution was suggested with supposition that the lessen the deposit metal size a little by changing to the finer wire diameter can reduce the actual heat input and heat accumulation during the WAAM process. In this research, the WAAM of AZ31B has been conducted using a wire diameter of 1.0 mm rather using the 1.2 mm that is used in common. It was found that the finer (about 90 %) and equiaxed microstructure was composing the WAAM product made of wire diameter of 1.0 mm, and it results in about two times higher mechanical strength.

Tribological and electrochemical behaviors of FeCoNiCrMox HEA coatings prepared by internal laser cladding on 316L steel tube

In order to improve the performance of the inner wall of the 316L hydraulic cylinder, FeCoNiCrMox (x = 0.2, 0.4, 0.6) high entropy alloy coatings were prepared by laser cladding. The effects of the Mo element on the phase, microstructure, hardness, and tribological as well as electrochemical behaviors of the coating were investigated. The results show that the coatings consist of the FCC phase. The FCC phase increases, and the grain orientation becomes more complex with increased Mo element content. The coatings are mainly composed of columnar and equiaxial crystals. Mo0.4 coating has the finest grain structure, resulting in the coating with a maximum hardness of 421.99 HV, 2.11 times that of the substrate. The nanoindentation test shows that the elastic modulus of the HEA coating increases with the increase of Mo content. The dry sliding wear test shows that adding the Mo element improves the wear performance of the coating. The wear volume loss and wear rate of Mo0.4 coating were the lowest, 12.242 mg and 2.88 × 10−4 mm3•N−1•m−1, respectively. In the 3.5 wt% NaCl solution, the polarization curves and EIS results indicated that adding the Mo element improved the corrosion resistance of the coating. The FeCoNiCrMox coatings significantly improved the hardness, tribological, and electrochemical behaviors of the 316L substrate.

Characterization of flexural fatigue behaviour of additively manufactured (PBF–LB) gyroid structures

AbstractAdditive manufacturing (AM) holds remarkable potential for producing cellular materials with intricate structures and tailored mechanical properties. The study investigates the flexural fatigue behaviour of additively manufactured triply periodic minimal surface (TPMS) gyroid structures using laser powder bed fusion (PBF–LB) technique. The fatigue properties, especially the bending fatigue properties, of additively manufactured cellular structures are not well understood to date. The research aims to enhance understanding of bending fatigue in complex cellular geometries and assess the suitability of rotating bending tests. The PBF–LB process parameters were modified to study their impact on the specimen’s fatigue properties. The modified parameters led to increased surface roughness but significantly improved fatigue behaviour. This enhancement is attributed to a reduction in build defects, namely pores and finer grain size in thin-walled structures. The study also includes analysis of microstructure, hardness, surface roughness, and porosity of the specimens. The results indicate that optimizing process parameters for thin walled cellular structures can lead to substantial improvements in fatigue strength, at the expense of increased surface roughness. This finding offers practical insights for applications in which a rough surface finish may not be critical or even intentionally desired by the application. The research contributes to the understanding of additive manufacturing, cellular structures, and material testing, with potential implications for materials science and engineering applications.

Design and characterization of (TiZr)95-xHfxMo5 multi-principal element alloys with excellent properties for biomedical applications

Developing new bio-metallic materials with improved performance has attracted intensive research focus over the last decades. In the present work, a new series of (TiZr)95-xHfxMo5 (x = 0, 10, 15, 20, 25, 31.67) multi-principal elements alloys (MPEAs) have been designed for potential implant materials. The mechanical properties, deformation characteristics, tribological properties, corrosion resistance, and in vitro biocompatibility of the MPEAs were characterized. All the TiZrHfMo alloys possess a high yield strength (913–––1083 MPa) and tensile strength (931–––1118 MPa) and a large microhardness (296–––333 Hv). The addition of Hf into the alloys induced severe lattice distortion, which increased the solid-solution strengthening effect. It also resulted in a finer grain size and led to excellent wear resistance. Meanwhile, the results showed that the dislocation glide mode transformed from planar slip to cross-slip and the transformation became apparent with the decrease of Hf. Also, the MPEAs showed a good corrosion resistance compared to CP-Ti, which was credited to the superior passivation films. The in vitro biocompatibility experiments displayed that the TiZrHfMo alloys exhibited high cell viability ratios, which were close to that of CP-Ti. The present work demonstrates the huge potential of TiZrHfMo MPEAs as implant material for biomedical applications.

Influence of Ti addition on the microstructure and comprehensive properties of Mo–Cu alloy

To enhance the overall performance of Mo–Cu alloy, Ti was added to Mo–Cu alloy to improve the bonding strength of Mo/Cu interface and generate solid solution strengthening effect. The outstanding performances of Mo–Cu–Ti alloys were achieved by infiltrating Cu–Ti alloy with different compositions into the Mo skeleton. Compared to the incoherent interface of Mo/Cu in Mo–Cu alloy, the addition of Ti transformed its interface to the coherent interface of Mo–Ti/Cu–Ti. All Mo–Cu–Ti alloy blocks had higher relative densities (97.4%∼98.5%) to guarantee the excellent comprehensive performances. What's more, the existences of Mo–Ti and Cu–Ti solid solutions assured the alloy possessed relatively high mechanical strength. The introduction of Ti purified the grain boundary by absorbing oxygen to generate TiO2 which hindered the growth of Mo–Ti grains. As increasing Ti amount from 0 wt% to 4.62 wt%, the Mo–Ti (or Mo) grain size reduced from 5 μm to 4.1 μm. Notably, Mo–Cu alloy block with the addition of 2.30 wt% Ti possessed the highest tensile strength of 562 MPa. Additionally, since the finer grain size of Mo–Ti alloy, this sample also owned the maximum micro-hardness and bending strength of 268 HV and 1730 MPa, respectively. Nevertheless, the presences of Cu–Ti solid solution and TiO2 also destroyed the electrical conductivities of the samples to some extent.

Exploring the Influence of Nanocrystalline Structure and Aluminum Content on High-Temperature Oxidation Behavior of Fe-Cr-Al Alloys.

The present study examines the high-temperature (500-800 °C) oxidation behavior of Fe-10Cr-(3,5) Al alloys and studies the effect of nanocrystalline structure and Al content on their resistance to oxidation. The nanocrystalline (NC) alloy powder was synthesized via planetary ball milling. The prepared NC alloy powder was consolidated using spark plasma sintering to form NC alloys. Subsequently, an annealing of the NC alloys was performed to transform them into microcrystalline (MC) alloys. It was observed that the NC alloys exhibit superior resistance to oxidation compared to their MC counterparts at high temperatures. The superior resistance to oxidation of the NC alloys is attributed to their considerably finer grain size, which enhances the diffusion of those elements to the metal-oxide interface that forms the protective oxide layer. Conversely, the coarser grain size in MC alloys limits the diffusion of the oxide-forming components. Furthermore, the Fe-10Cr-5Al alloy showed greater resistance to oxidation than the Fe-10Cr-3Al alloy.

The dynamic recrystallization microstructure characteristics and the effects on static recrystallization and mechanical properties of Al–Mg–Si alloy

It is essential to clarify the dynamic recrystallization microstructure characteristics of age-hardened aluminum alloys and the effects on the static recrystallization microstructure and aging mechanical properties, with the aim of selecting the deformation conditions reasonably. This work investigated the evolution of the hot deformation and solid solution microstructures and aging mechanical properties of Al–Mg–Si alloy with deformation temperatures of 400–550 °C, strain rates of 0.01–10 s−1, and true strains of 0.2–0.8. Research has shown that it is advantageous for the DDRX and CDRX mechanisms to annihilate and rearrange dislocations simultaneously for forming deformation microstructure with uniform grain size at higher deformation temperatures and lower strain rates (such as 500 °C, 0.01 s−1). Additionally, the lower dislocation density in deformation microstructure facilitated the inhibition of static recrystallization during subsequent solid solution treatment, whereas lower deformation temperature and higher strain rate conditions should result in a greater degree of static recrystallization and reduce the uniformity of the solid solution microstructure. Hardness test results demonstrated that the deformation temperature of 480–520 °C and strain rate of 0.03–0.2 s−1 were the appropriate conditions for Al–Mg–Si alloy to attain finer and uniform grains and superior properties after solid solution treatment. The extruded samples within the above conditions (500 °C, 0.032 s−1) exhibited higher UTS and YS after solid solution and aging treatment, reaching 444 ± 2 MPa and 426 ± 4 MPa, respectively.

Effect of Wire Preheat and Feed Rate in X80 Steel Laser Root Welds: Part 1 — Microstructure

Laser welding with cold versus hot wire feed was employed as a root pass to weld X80 pipeline steel. The influences of wire feed rate and preheat on the fusion zone microstructure were investigated. Increasing the wire feed rate helped generate acicular ferrite in the weld metal, and preheating the wire further suppressed the formation of bainite. The acicular ferrite in the upper region of the fusion zone was finer than that in the lower region, which was due to an increase in nucleation sites available. Five fill and cap passes were applied by gas metal arc welding to fill the remaining top part of the groove. Compared to arc welding with a higher heat input, laser welding led to finer prior austenite grains and smaller bainite packet size in the coarse-grained heat-affected zone and limited the formation of martensite-austenite constituents in the intercritically reheated coarse-grained heat-affected zone.

Development of electroforming technology for flexible metal substrates for high-efficiency double-sided electronic devices

In this study, we investigate a novel material that surpasses conventional concepts used for substrate materials in flexible electronic devices. Unlike traditional materials, this novel material can replace polymers with a metallic substance. This substance is capable of supporting electronic devices on both sides. Our development focuses on a metallic substrate material based on Fe-Ni. This material allows for the implementation of secondary batteries on its extremely flat opposite side through the electroforming method. The Fe (Iron)-Ni (Nickel) material produced by electroforming shows superior characteristics in terms of coefficient of thermal expansion (CTE) and mechanical properties. This superiority is due to its finer grain size, compared to Fe-Ni produced by the rolling process. Furthermore, when we use the Fe-Ni material to manufacture secondary batteries, it demonstrates equivalent or superior battery characteristics compared to the conventional aluminum (Al) collector material. During thermal shock tests, the Fe-Ni material also shows superior adhesion compared to the traditional Al collector. This advantage is attributed to Fe-Ni's low CTE. Our approach enables the implementation of secondary batteries for power generation on one side and the manufacture of electronic components for power consumption on the other. This creates a new concept for flexible substrate materials.

Influence of CrCuFeMnNi high entropy alloy particle on the microstructure and mechanical properties of aerospace-grade aluminum 7075 metal-metal composite

This study investigates the formation of nano-crystalline CrCuFeMnNi high entropy alloy particles and influence on aluminum 7075 matrix. The mechanical alloying process successfully synthesized HEA particles with nearly equiatomic composition and excellent chemical homogeneity. To fabricate the HEA-based aluminum composite, a novel casting technique combining a modified bottom pouring stir casting furnace integrated with a mechanical supersonic vibrator and squeeze infiltration setup was employed. Optical microscopy, SEM-EDS, BSE, and EBSD techniques confirmed the uniform distribution of HEA particles within AA7075 matrix. Notably, the AA7075-15wt.% HEAp composite exhibited a significantly finer grain size compared to the AA7075-5wt.% and 10wt.% HEAp composites. The mechanical properties, including hardness, tensile and yield strength, flexural strength, and impact strength of the AA7075-HEAp composite were investigated.

Enhancement of Strength-Ductility Synergy of Al-Li Cast Alloy via New Forming Processes and Sc Addition.

In this study, concurrent enhancements in both strength and ductility of the Al-2Li-2Cu-0.5Mg-0.2Zr cast alloy (hereafter referred to as Al-Li) were achieved through an optimized forming process comprising ultrasonic treatment followed by squeeze casting, coupled with the incorporation of Sc. Initially, the variations in the microstructure and mechanical properties of the Sc-free Al-Li cast alloy (i.e., alloy A) during various forming processes were investigated. The results revealed that the grain size in the UT+SC (ultrasonic treatment + squeeze casting) alloy was reduced by 76.3% and 57.7%, respectively, compared to those of the GC (gravity casting) or SC alloys. Additionally, significant improvements were observed in its compositional segregation and porosity reduction. After UT+SC, the ultimate tensile strength (UTS), yield strength (YS), and elongation reached 235 MPa, 135 MPa, and 15%, respectively, which were 113.6%, 28.6%, and 1150% higher than those of the GC alloy. Subsequently, the Al-Li cast alloy containing 0.2 wt.% Sc (referred to as alloy B) exhibited even finer grains under the UT+SC process, resulting in simultaneous enhancements in its UTS, YS, and elongation. Interestingly, the product of ultimate tensile strength and elongation (i.e., UTS × EL) for both alloys reached 36 GPa•% and 42 GPa•%, respectively, which is much higher than that of other Al-Li cast alloys reported in the available literature.

Metamorphic evolution of sillimanite gneiss in the high-pressure terrane of the Western Gneiss Region (Norway)

Abstract. Sillimanite-bearing gneisses in the Romsdal region of the Western Gneiss Region (south Norway) have been investigated to document the presence, formation, composition and petrological evolution of the sillimanite-bearing assemblages. Sillimanite is found in augen gneiss, as nodular gneiss, and in well-foliated sillimanite–mica gneiss. Lenses and layers of eclogite occur within the gneiss units. The sillimanite-bearing gneisses are heterogranular and dominated by quartz, plagioclase (An29–41), K-feldspar and biotite (Mg# = 0.48–0.58; Ti = 0.16–0.36 a.p.f.u.), with variable amounts of white mica (Si = 6.1–6.3). K-feldspar occurs as porphyroclasts in augen gneiss, and garnet constitutes resorbed porphyroblasts. Garnet (Alm46–56Sps24–36Prp10−20Grs4–6; Mg# = 0.22–0.29) shows rimward-decreasing Mg#, together with a smaller grossular decrease and a marked spessartine increase up to Sps36. The foliation is defined by crystal-preferred-orientation micas, elongation of shape-preferred-orientation coarse K-feldspar phenocrysts and a modal banding of phases. Sillimanite occurs as coarse orientation-parallel matrix porphyroblasts, as finer grains and as fibrolitic aggregates. Quartz constitutes coarser elongated grains and monomineralic rods. Pseudosection modelling suggests that the peak-metamorphic mineral assemblage of garnet–sillimanite–feldspar–biotite–quartz–ilmenite–liquid equilibrated at temperatures up to 750 °C and pressures of 0.6 GPa. Subsequent retrogression consumed garnet. Mineral replacement and melt crystallization involved sillimanite, white mica, K-feldspar and quartz. The results document a metamorphic retrogression of the sillimanite gneisses in accordance with the presence of remnants of eclogites and high-pressure granulites in this northwestern part of the Western Gneiss Region.

Impact of friction stir welding parameters and Al2TiO5 reinforcement on the mechanical, wear, and corrosion performance of dissimilar welded aluminium composite joints

This study investigates the impact of friction stir welding (FSW) parameters on dissimilar AA5052-Al2TiO5/AA6061-Al2TiO5 composite joints. Tool rotational speed (TRS), feed rate, and aluminum titanate (Al2TiO5) content are varied, and their influence on microstructure, mechanical properties, wear resistance, and corrosion behavior is assessed. Joints fabricated with 1200 rpm TRS, 40 mm/min feed rate, and 2 wt% Al2TiO5 exhibit the highest tensile strength (170.11 MPa) due to grain refinement in the stir zone (SZ). Joints with 3 wt% Al2TiO5 have near-base composite hardness (86.12 HV) and exhibit distinct microstructures across different zones. Samples with superior mechanical properties display finer grains in the SZ, while other zones exhibit elongated grains. The sample reinforced with 3 wt% Al2TiO5 (W9) demonstrates enhanced wear resistance attributed to its high hardness. Additionally, the sample fabricated with 1200 rpm TRS, 40 mm/min feed rate, and 2 wt% Al2TiO5 (W15) displays the lowest corrosion rate (0.44 mpy) due to its fine structure. Fracture analysis reveals different failure mechanisms in tensile and wear testing.

Toward high strength and large strain hardening Zn alloys via a novel multiscale-heterostructure strategy

Zn alloy has attracted much attention as a biodegradable material for biomedical applications. However, due to the significant strain softening of Zn alloys, how to break the bottleneck of synergistic yield strength and uniform elongation is an urgent problem to be solved. In this work, a Zn-2.3Cu-0.8Mn (wt.%) alloy was fabricated via low-temperature extrusion and annealing at 330 °C for 1 h to attain dual heterostructures with bimodal grains and multi-scale second phases, focusing on the effect of heterostructure on the mechanical properties. Uniaxial tensile test and loading-unloading-reloading test were applied to reveal the mechanical properties of the Zn-2.3Cu-0.8Mn alloy, while scanning electron microscope, electron backscatter diffraction, and transmission electron microscope were used to characterize its microstructure. Compared with the as-extruded alloy with uniform and fine grains, 330–1 alloy achieves a better combination of strength and uniform elongation (yield strength: 287.8 ± 8.5 MPa, ultimate tensile strength: 321.4 ± 6.8 MPa, and uniform elongation: 14.2 ± 1.8%). The high strength was primarily attributed to the coordination of grain boundary strengthening, hetero-deformation induced strengthening, Orowan strengthening, and dislocation strengthening. Besides, the coarse grains, twinning, as well as the suppression of grain boundary sliding and phase boundary sliding promoted dislocation proliferation and storage capacity, thereby improving work hardening capacity. The large strain hardening capacity was responsible for excellent plasticity. This study provides a feasible strategy for the design of Zn-based alloys with an excellent combination of high strength and strain hardening capacity.

Pressureless two-step sintering of ultrafine-grained high-entropy zirconate ceramics with excellent mechanical properties

The challenge of preparing dense ultrafine-grained high-entropy ceramics through conventional pressureless sintering is hereby addressed by a simple two-step sintering method. Ultrafine-grained (Ce0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 high-entropy zirconate with 99.2 % theoretical density and 135 nm grain size has been fabricated by pressureless two-step sintering for the first time. Compared to the conventional sintering, two-step sintering provides finer grain sizes and better microstructural uniformity, which yield excellent comprehensive mechanical properties with high hardness of 16.0 GPa, large elastic modulus of 262 GPa and high fracture toughness of 2.8 MPa·m1/2. It is believe that pressureless two-step sintering can be utilized to prepare other high-entropy ceramics with fine grain size and high quality.

Stable production of dissimilar steel joints in construction machinery by narrow gap oscillating laser welding

Narrow gap oscillating laser welding with filler wire is a promising technique for joining high-strength steels in construction machinery. In order to investigate the influence of beam oscillation on the surface morphology and microstructure of weld joints of two types of commonly-used high-strength steels, a comparative study between oscillation welding and non-oscillation welding was conducted. High-speed photography technique was employed to reveal the microstructure and mechanical properties of the dissimilar joints. The results showed that laser beam oscillation produces two effects: one was to enlarge the heated surface of molten pool, while the other was to stir the liquid metal in molten pool periodically. Under the first effect, the fusion between sidewall and weld bead layers was promoted, while under the latter, coarse columnar grains ceased to appear, but finer grains were formed. The weld joints between Q355 and 35 steels exhibited excellent tensile impact bending performance, which was attributed to the grain refinement effect. The results also demonstrated that the oscillation welding with a contact angle less than 50° could avoid lack of fusion in multi-pass wire-filling laser welding. The influence of the oscillation welding process on the quality of welding was further discussed.

Movement Strategy Influences on the Characteristics of Low-Carbon Steel Generated by the Lamination Object Manufacturing Method

This paper investigates the effects of heating movement techniques on the properties of low-carbon steel samples that are 3D printed using S20C lamination object manufacturing (LOM). A Tungsten iner gas (TIG) machine and a computer numerical control (CNC) machine were used together to join the steel sheet. The LOM samples were created with a straight-profile, short-profile, cross-profile, and curved-profile. The results indicate that the majority of the samples had a grain size number of 7–9. The samples exhibited an isotropy grain shape. The LOM samples exhibited dimples, which suggests ductility fractures. Pore flaws showed up in the microstructure of the cross-profile and short-profile samples during the LOM process. The samples with curved- and straight-profiles had a better microstructure. In comparison to samples with a short profile and a cross-profile, the samples with a straight-profile and a curved-profile had a superior combination of ultimate tensile strengths (UTSs) and elongation value. The straight- and curved-profiles’ greater elongation and tensile strength can be attributed to their improved microstructure and finer grain size. A straight-profile sample with an elongation value of 25.6% and a UTS value of 430 MPa was the ideal LOM sample. Conversely, the weakest sample was the LOM sample with a cross-profile, which had an elongation value of 10.8% and a UTS value of 332.5 MPa. This research could provide further information about the LOM method and the best straight-profile movement strategy. A suitable TIG gun movement strategy could produce a good LOM sample with a good microstructure, tensile strength, and ductility. Further research should incorporate more movement strategies and techniques that completely prevent the formation of pore defects.

Fabrication of crack-free aluminum alloy 6061 parts using laser foil printing process

PurposeThis paper aims to present the fabrication of 6061 aluminum alloy (AA6061) using a promising laser additive manufacturing process, called the laser-foil-printing (LFP) process. The process window of AA6061 in LFP was established to optimize process parameters for the fabrication of high strength, dense and crack-free parts even though AA6061 is challenging for laser additive manufacturing processes due to hot-cracking issues.Design/methodology/approachThe multilayers AA6061 parts were fabricated by LFP to characterize for cracks and porosity. Mechanical properties of the LFP-fabricated AA6061 parts were tested using Vicker’s microhardness and tensile testes. The electron backscattered diffraction (EBSD) technique was used to reveal the grain structure and preferred orientation of AA6061 parts.FindingsThe crack-free AA6061 parts with a high relative density of 99.8% were successfully fabricated using the optimal process parameters in LFP. The LFP-fabricated parts exhibited exceptional tensile strength and comparable ductility compared to AA6061 samples fabricated by conventional laser powder bed fusion (LPBF) processes. The EBSD result shows the formation of cracks was correlated with the cooling rate of the melt pool as cracks tended to develop within finer grain structures, which were formed in a shorter solidification time and higher cooling rate.Originality/valueThis study presents the pioneering achievement of fabricating crack-free AA6061 parts using LFP without the necessity of preheating the substrate or mixing nanoparticles into the melt pool during the laser melting. The study includes a comprehensive examination of both the mechanical properties and grain structures, with comparisons made to parts produced through the traditional LPBF method.