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The primary carbide in high carbon chromium bearing steels, which arises from solute segregation during non-equilibrium solidification, is one of the key factors affecting the mechanical properties and performance of the related components. In this work, the effects of carbide forming element diffusion, primary austenite grain size, and the cooling rate on solute segregation and carbide precipitation during the solidification of an Fe–C binary alloy were studied by the phase-field method coupled with a thermodynamic database. It was clarified that increasing the ratio of solute diffusivity in solid and liquid, refining the grain size of primary austenite to lower than a critical value, and increasing the cooling rate can reduce the solute segregation and precipitation of primary carbide at late solidification. Two characteristic parameters were introduced to quantitatively evaluate the solute segregation during solidification including the phase fraction threshold of primary austenite when the solute concentration in liquid reaches the eutectic composition, and the maximum segregation ratio. Both parameters can be well-correlated to the ratio of solute diffusivity in solid and liquid, the grain size of primary austenite, and the cooling rate, which provides potential ways to control the solute segregation and precipitation of primary carbide in bearing steels.

Rare earth (RE) addition to steels to produce RE steels has been widely applied when aiming to improve steel properties. However, RE steels have exhibited extremely variable mechanical performances, which has become a bottleneck in the past few decades for their production, utilization and related study. Here in this work, we discovered that the property variation of RE steels stems from the presence of oxygen-based inclusions. We proposed a dual low-oxygen technology, and keeping low levels of oxygen content in steel melts and particularly in the raw RE materials, which have long been ignored, to achieve impressively stable and favourable RE effects. The fatigue life is greatly improved by only parts-per-million-level RE addition, with a 40-fold improvement for the tension-compression fatigue life and a 40% enhancement of the rolling contact fatigue life. We find that RE appears to act by lowering the carbon diffusion rate and by retarding ferrite nucleation at the austenite grain boundaries. Our study reveals that only under very low-oxygen conditions can RE perform a vital role in purifying, modifying and micro-alloying steels, to improve the performance of RE steels.

Excellent high-temperature mechanical properties of Ni-based single crystal superalloys (NSCSs) are attributed to the yield strength anomaly of Ni$_{3}$Al that is intimately related to generalized stacking fault energies (GSFEs). Therefore, clarifying the effects of alloying elements on the GSFEs is of great significance for alloys design. Here, by means of ab initio density functional theory calculations, we systematically calculated the GSFEs of different slip systems of Ni and Ni$_{3}$Al without and with alloying elements using the alias shear method. We obtained that for Ni, except for magnetic elements Mn, Fe, and Co, most of alloying elements decrease the unstable stacking fault energy ($\gamma_{usf}$) of the $[01\bar{1}](111)$ and $[11\bar{2}](111)$ slip systems and also decrease the stable stacking fault energy ($\gamma_{sf}$) of the $[11\bar{2}](111)$ slip system. For Ni$_{3}$Al, most of alloying elements in groups IIIB-VIIB show a strong Al site preference. Except for Mn and Fe, the elements in groups VB-VIIB and the first column of group VIII increase the values of $\gamma_{usf}$ of different slip systems of Ni$_{3}$Al. On the other hand, the elements in groups IIIB-VIIB also increase the value of $\gamma_{sf}$. We found that Re is an excellent strengthening alloying element that significantly increases the slip barrier of the tailing slip process for Ni, and also enhances the slip barrier of the leading slip process of three slip systems for Ni$_{3}$Al. W and Mo exhibit similar effects as Re. We predicted that Os, Ru, and Ir are good strengthening alloying elements as well, since they show the strengthening effects on both the leading and tailing slip process for Ni and Ni$_{3}$Al.

Two-dimensional layered MSi2N4 (M = Mo, W) as promising thermal management materials: a comparative study.

The number and stacking order of layers are two important degrees of freedom that can modulate the properties of 2D van der Waals (vdW) materials. However, the layers’ structures are essentially limited to the known layered 3D vdW materials. Recently, a new 2D vdW material, MoSi2N4, without known 3D counterparts, was synthesized by passivating the surface dangling bonds of non-layered 2D molybdenum nitride with elemental silicon, whose monolayer can be viewed as a monolayer MoN (-N-Mo-N-) sandwiched between two Si-N layers. This unique sandwich structure endows the MoSi2N4 monolayer with many fascinating properties and intriguing applications, and the surface-passivating growth method creates the possibility of tuning the layer's structure of 2D vdW materials. Here we synthesized a series of MoSi2N4(MoN)4n structures confined in the matrix of multilayer MoSi2N4. These super-thick monolayers are the homologous compounds of MoSi2N4, which can be viewed as multilayer MoN (Mo4n+1N4n+2) sandwiched between two Si-N layers. First-principles calculations show that MoSi2N4(MoN)4 monolayers have much higher Young's modulus than MoN, which is attributed to the strong Si-N bonds on the surface. Importantly, different from the semiconducting nature of the MoSi2N4 monolayer, the MoSi2N4(MoN)4 monolayer is identified as a superconductor with a transition temperature of 9.02 K. The discovery of MoSi2N4(MoN)4n structures not only expands the family of 2D materials but also brings a new degree of freedom to tailor the structure of 2D vdW materials, which may lead to unexpected novel properties and applications.

Over the past decade, utilizing spin currents in the linear response of electric field to manipulate magnetization states via spin-orbit torques (SOTs) is one of the core concepts for realizing a multitude of spintronic devices. Besides the linear regime, recently, nonlinear charge-spin conversion under the square of electric field has been recognized in a wide variety of materials with nontrivial spin textures, opening an emerging field of nonlinear spintronics. Here, we report the investigation of both linear and nonlinear charge-spin conversion in one single topological semimetal SrIrO3(110) thin film that hosts strong spin-orbit coupling and nontrivial spin textures in the momentum space. In the nonlinear regime, the observation of crystalline direction dependent response indicates the presence of anisotropic surface states induced spin-momentum locking near the Fermi level. Such anisotropic spin textures also give rise to spin currents in the linear response regime, which mainly contributes to the fieldlike SOT component. Our work demonstrates the power of combination of linear and nonlinear approaches in understanding and utilizing charge-spin conversion in topological materials., 18 pages, 5 figures

Microsegregation formed during solidification is of great importance to material properties. The conventional Lever rule and Scheil equation are widely used to predict solute segregation. However, these models always fail to predict the exact solute concentration at a high solid fraction because of theoretical assumptions. Here, the dynamics of microsegregation during polycrystalline solidification of refined Al-Cu alloy is studied via two- and three-dimensional quantitative phase-field simulations. Simulations with different grain refinement level, cooling rate, and solid diffusion coefficient demonstrate that solute segregation at the end of solidification (i.e. when the solid fraction is close to unit) is not strongly correlated to the grain morphology and back diffusion. These independences are in accordance with the Scheil equation which only relates to the solid fraction, but the model predicts a much higher liquid concentration than simulations. Accordingly, based on the quantitative phase-field simulations, a new analytical microsegregation model is derived. Unlike the Scheil equation or the Lever rule that respectively overestimates or underestimates the liquid concentration, the present model predicts the liquid concentration in a pretty good agreement with phase-field simulations, particularly at the late solidification stage.

The search for new two-dimensional monolayers with diverse electronic properties has attracted growing interest in recent years. Here, we present an approach to construct MA2Z4 monolayers with a septuple-atomic-layer structure, that is, intercalating a MoS2-type monolayer MZ2 into an InSe-type monolayer A2Z2. We illustrate this unique strategy by means of first-principles calculations, which not only reproduce the structures of MoSi2N4 and MnBi2Te4 that were already experimentally synthesized, but also predict 72 compounds that are thermodynamically and dynamically stable. Such an intercalated architecture significantly reconstructs the band structures of the constituents MZ2 and A2Z2, leading to diverse electronic properties for MA2Z4, which can be classified according to the total number of valence electrons. The systems with 32 and 34 valence electrons are mostly semiconductors. Whereas, those with 33 valence electrons can be nonmagnetic metals or ferromagnetic semiconductors. In particular, we find that, among the predicted compounds, (Ca,Sr)Ga2Te4 are topologically nontrivial by both the standard density functional theory and hybrid functional calculations. While VSi2P4 is a ferromagnetic semiconductor and TaSi2N4 is a type-I Ising superconductor. Moreover, WSi2P4 is a direct gap semiconductor with peculiar spin-valley properties, which are robust against interlayer interactions. Our study thus provides an effective way of designing septuple-atomic-layer MA2Z4 with unusual electronic properties to draw immediate experimental interest., The discovery of a new two-dimensional van der Waals layered MoSi2N4 material inspires many attentions. Here, the authors report intercalation strategies to explore a much wider range of MA2Z4 family and predict amount of materials accessible to experimental verifications with emergent topological, magnetic or Ising superconductivity properties.

Refining grains to the nanoscale can greatly enhance the strength of metals. But so far the fabrication routes of nanostructured metals are difficult to be applied at a large-scale industrial level owing to their high cost and size limitation. More crucially, the superior properties of nanostructured metals are easily lost during thermoforming process due to their poor microstructural stability, which limits their widespread application in engineering practice. Here we report a facile “Eutectoid element alloying→Quenching→Hot deformation” (EQD) strategy, which enables the mass production of a Ti6Al4V5Cu model alloy with α-Ti grain size of 95 ± 32 nm. In addition, rapid co-precipitation of Ti2Cu and β phases forms a “dual-phase honeycomb shell” (DPHS) structure along the grain boundaries and effectively stabilizes the nanosized α-grains. The instability temperature of the nanostructured Ti6Al4V5Cu alloy reaches 973 K (0.55Tm). The room temperature tensile strength approaches 1.52 ± 0.03 GPa, which is 60% higher than the Ti6Al4V counterpart without sacrificing its ductility. Furthermore, the tensile elongation at 923 K exceeds 1000%, more than ten times higher than the Ti6Al4V counterpart. Grain growth is not observed even under such an extreme thermal-mechanical coupling condition. This enables nanostructured Ti6Al4V5Cu to be easily shaped to complex components. The aforementioned strategy paves a new pathway to develop manufacture-friendly, high-performance metallic materials and it also has a great potential to be applied in other alloy systems.

The discovery of topological quantum states marks a new chapter in both condensed matter physics and materials sciences. By analogy to spin electronic system, topological concepts have been extended into phonons, boosting the birth of topological phononics (TPs). Here, we present a high-throughput screening and data-driven approach to compute and evaluate TPs among over 10,000 real materials. We have discovered 5014 TP materials and grouped them into two main classes of Weyl and nodal-line (ring) TPs. We have clarified the physical mechanism for the occurrence of single Weyl, high degenerate Weyl, individual nodal-line (ring), nodal-link, nodal-chain, and nodal-net TPs in various materials and their mutual correlations. Among the phononic systems, we have predicted the hourglass nodal net TPs in TeO3, as well as the clean and single type-I Weyl TPs between the acoustic and optical branches in half-Heusler LiCaAs. In addition, we found that different types of TPs can coexist in many materials (such as ScZn). Their potential applications and experimental detections have been discussed. This work substantially increases the amount of TP materials, which enables an in-depth investigation of their structure-property relations and opens new avenues for future device design related to TPs., Topological phononic (TP) materials are attracting wide attentions and it is more difficult to seek TP materials compared to electronic materials. Here, the authors present a high-throughput screening and data-driven approach to discover 5014 TP materials and further clarify the mechanism for the occurrence of various TPs.

The realization of multifunctional two-dimensional (2D) materials is fundamentally intriguing, such as the combination of piezoelectricity with a topological insulating phase or ferromagnetism. In this work, a Janus monolayer SrAlGaSe4 is built from the 2D MA2Z4 family with dynamic, mechanical and thermal stabilities, which is piezoelectric due to the lack of inversion symmetry. The unstrained SrAlGaSe4 monolayer is a narrow gap normal insulator (NI) with spin orbital coupling (SOC). However, the NI to topological insulator (TI) phase transition can be induced by biaxial strain, and a piezoelectric quantum spin Hall insulator (PQSHI) can be achieved. More excitingly, the phase transformation point is only about 1.01 tensile strain, and the nontrivial band topology can hold until the considered 1.16 tensile strain. Moreover, Rashba spin splitting in the conduction bands can exist in a PQSHI due to the absence of a horizontal mirror symmetry and the presence of SOC. For monolayer SrAlGaSe4, both in-plane and very weak out-of-plane piezoelectric polarizations can be induced with the application of uniaxial strain. The calculated piezoelectric strain coefficients d11 and d31 of monolayer SrAlGaSe4 are −1.865 pm V−1 and −0.068 pm V−1 at 1.06 tensile strain as a representative TI. In fact, many PQSHIs can be realized from the 2D MA2Z4 family. To confirm that, similar to SrAlGaSe4, the coexistence of piezoelectricity and topological orders can be realized by applying strain (about 1.04 tensile strain) in the CaAlGaSe4 monolayer. This study suggests that Janus monolayer SrAlGaSe4 is a pure 2D system for a PQSHI, enabling future studies exploring the interplay between piezoelectricity and topological order, which can lead to novel applications in electronics and spintronics.

Using ab initio density functional approach, we analyze the trapping behavior of Hydrogen atom in a series fcc structure metals (M = Ni, Cu and Al). From the calculations we found that the potential trapping sites in all these three metals is strongly correlated with the electron charges distribution and the swelling of the nH-Vac cluster is largely determined by the transferring charges of the metal atoms around the vacancy. According to our results, in both intrinsic metals and the metal with monovacancy the hydrogen atoms are always prone to be trapped at the interstitial site with large pre-existed charges and the growth of nH-Vac cluster greatly depends on the charges supplying by the surrounding metal atoms. By our calculations the deficit charges supplying by the nearby metal atoms always accompany a strain energy increment which forbid the nH-Vac swelling. This mechanism is identified in all these three fcc metals. We also found that the formation of hydrogen molecule at the center of the vacancy can only be identified in Aluminum no matter the trapping sites around the vacancy are fully occupied or not. But in Ni and Cu with the same fcc structure H2 molecule are not popular.

Adsorption of carbon monoxide (CO) on transition-metal surfaces is a prototypical process in surface sciences and catalysis. Despite its simplicity, it has posed great challenges to theoretical modeling. Pretty much all existing density functionals fail to accurately describe surface energies, CO adsorption site preference, as well as adsorption energies simultaneously. Although the random phase approximation (RPA) cures these density functional theory failures, its large computational cost makes it prohibitive to study the CO adsorption for any but the simplest ordered cases. Here, we address these challenges by developing a machine-learned force field (MLFF) with near RPA accuracy for the prediction of coverage-dependent adsorption of CO on the Rh(111) surface through an efficient on-the-fly active learning procedure and a $\Delta$-machine learning approach. We show that the RPA-derived MLFF is capable to accurately predict the Rh(111) surface energy, CO adsorption site preference as well as adsorption energies at different coverages that are all in good agreement with experiments. Moreover, the coverage-dependent ground-state adsorption patterns and adsorption saturation coverage are identified., Comment: 6 pages, 2 figures

The systematic investigation on the U–H binary system up to 300 GPa has been performed by means of first-principles calculations in combination with the variable-composition evolutionary algorithm. Twenty uranium hydrides, including UHx (x = 1, 2, 3, 4, 5, 6, 7, 8, 9, 17), U2Hy (y = 3, 5, 7, 13, 15, 17), U3H8, U3H10, U4H5 and U4H9 have been found under different pressures. Besides thirteen compounds that are in nice agreement with previously reported structural search, new uranium hydrides in terms of the derived convex hull of the formation enthalpies have also been found in the present investigation. These seven novel compounds including Cmcm-UH3, Fmmm-UH4, R 3 ‾ m-U2H7, Pm–U2H15, Cm–U3H8, C2–U4H9 and C2/m-U4H5, are found to be dynamically and thermodynamically stable, and their stable pressure range has been determined. At last, the electronic and mechanical properties of these seven novel structures have further been calculated.

By means of first-principles calculations, we have proposed an ab initio modeling to establish a formula between the hydrogen evolution rate and its overpotential of hydrogen evolution reaction (HER), relating with three different rate determining mechanisms, when Volmer reaction, Tafel reaction and Heyrowsky reaction are the rate determining steps of the entire reaction, respectively. Within this modeling, the free energy ( Δ G H * ) of the adsorbed hydrogen atom and the concentration of hydrogen ions in the solution have been correlated to the exchange current density. The hydrogen evolution modeling has been validated by available experimental results. Furthermore, by combining the previously proposed first-principles modeling of the anodic dissolution and this modeling of the HER in the electrochemical corrosion, the polarization curves of the 18 crystallographic surfaces of pure Mg have been theoretically derived. It has been found that in a neutral solution ( p H = 7 ) the corrosion current densities (icorr) of the 18 crystallographic surfaces range from 10 − 3.477 to 10 − 0.455 A/cm2 and their corresponding corrosion potentials (Ecorr) range from −1.36 to −0.892 VSHE, respectively. The base (0001) surface exhibits a lower corrosion rate of 10 − 3.345 A/cm2, whereas the crystal (21 3 ¯ 0) surface has a fast corrosion rate of 10 − 0.455 A/cm2. The calculations even reveal that except for Ag, all the other alloying elements considered here accelerate the rates of the cathodic HER. In agreement with theoretical results, the experimentally measured polarization curves of the Mg-1Zn and Mg-2Sn alloys verify that both Zn and Sn additions accelerate the rate of the HER of Mg.

Several n- and p-type Half-Heusler (HH) thermoelectric materials (Ti0.5Zr0.5NiSn-based and NbFeSb-based) have been processed by high-pressure torsion (HPT) to improve their thermoelectric performance via a drastic reduction towards ultra-low thermal conductivity. This reduction occurs due to grain refinement and a high concentration of deformation-induced defects, i.e. vacancies and dislocations as inferred by this severe plastic deformation and documented via SEM and TEM investigations. In most cases the figure of merit, ZT, and the thermo-electric conversion efficiency were enhanced up to η ∼ 10% for the thermally stable HPT-processed sample. Raman spectroscopy, backed by DFT calculations, proves that HPT induces a stiffening of the lattice and as a consequence, a blue-shift of the lattice vibrations occurs. Furthermore for all investigated specimens Vickers hardness values after HPT were significantly higher, whereas the change in the elastic moduli was less than 5% in comparison to the HP reference sample.

The removal of interfacial oxides is essential in solid-state bonding to obtain high-performance joints. A recent work reported that the dissolution of MnCr2O4 at the hot compression bonding (HCB) interface of 316LN stainless steel improved the mechanical properties of joints. The evolution behaviors of interfacial oxides behind it should be further understood. In this study, the thermodynamic stability of MnCr2O4 and decomposition mechanisms of interfacial oxides in HCB was studied by combining the first-principles calculations with thermodynamics approach. The results obtained within GGA + U method were compared with experiments and in a good agreement with previous calculated results. The predicted stability region of MnCr2O4 was built by drawing the Mn-Cr-O phase diagram. The transition of its possibly coexisting binary oxides was understood in detail with respect to the environmental conditions. The interfacial oxides evolution in HCB process was proposed based on the variation of oxygen chemical potential. It predicted that MnCr2O4 forms during the heating period of HCB with the presence of binary oxides of Mn and Cr. All possible interfacial oxides decompose into metal phases and oxygen atoms when $$ \Delta \mu_{\text{O}} $$ is below − 386.97 kJ/mol.

By means of ab initio molecular dynamics (AIMD), we have evidenced the formation of the localized Nb clusters in the U-Nb liquid alloys even with the very low Nb concentrations. These localized Nb clusters are characterized, qualitatively and quantitatively, in terms of the pair correlation function, structure factor, coordination number and chemical short-range order parameters. The existence of the first highest peaks of the partial Nb-Nb pairs in both their pair correlation functions and structure factors reveals that the Nb atoms prefer to accumulate themselves together to form various localized clusters with three typical Nb networks of Nb2 dimers, opening chains (Nb3 or Nb4 chains) and closed triangles (Nb3 triangles) in the U-Nb liquid alloys. These Nb-Nb affinitive facts are further supported by the derived negative Nb-Nb chemical short-range order parameters. In contrast, both U-U and U-Nb interactions in these liquid alloys are further revealed to have the nearly zero, or positive, chemical short-range order parameters, corresponding to a relatively weak U-U, or repulsive U-Nb, interactions in the U-Nb liquid alloys.

In crystalline solids, to computationally determine atomic migration energy barrier is a highly time consuming challenge within the framework of Density Functional Theory (DFT). Through first-principle calculations, here we have proposed a simple, high-throughput formula to fast, effectively calculate atomic migration energy barrier for fcc metals through three basic parameters of materials, the equilibrium volume ( V 0 ), the bulk modulus ( B 0 ) and the Poisson's ratio (ν). This formula is useful not only for the ideal strain-free lattices but also for the uniaxially strained lattices. It has been further validated by a series of fcc metals when compared with both available experimental or theoretical data and DFT-derived data obtained by Nudged Elastic Band (NEB) method. Moreover, we have investigated the effect of uniaxial deformation on the diffusion behavior of vacancy in fcc metals. Our calculations revealed that in fcc metals under uniaxial tensile deformation, vacancy prefers to diffuse along the direction that is perpendicular to the uniaxial tensile deformation.

An experimental observation was reported that TiO2 nanoparticles promote α-Al2O3 direct growth on nickel aluminide by skipping the metastable-to-stable alumina transformation during the oxidation process. Mechanically, this direct growth of α-Al2O3 can be attributed to the fact that both α-Al2O3 and rutile-TiO2 nanoparticles share the well-matching sublattice of oxygen among their energetically favorable interfaces of (0 1 ¯ 0)TiO2//(000 1 ¯ )Al2O3, (0 1 ¯ 0)TiO2//( 1 ¯ 2 1 ¯ 0)Al2O3 and (001)TiO2//(10 1 ¯ 0)Al2O3. The work paves a new route to the controlling direct thermal growth of α-Al2O3 on the substrates of MxAly (M = Ni, Co, Fe)-based alloys by spreading the seed of a selected oxide which possesses the well-matching oxygen sublattice to α-Al2O3.

By means of ab initio molecular dynamics (AIMD), the evolution of local atomic structures of the U116Nb12 liquid alloy during solidification from 2600 K to 600 K was systemically investigated in terms of the pair correlation function, structure factor, bond angle distribution, coordination number, the Honeycutt-Anderson (HA) and Voronoi index as well as diffusivity and viscosity. The distinctly linear dependence of the mean square displacements (MSDs) as a function of time indicates that the equilibrium configurations are derived from our AIMD simulations. The equations of the volumetric expansion, thermal diffusion and viscosity of the U116Nb12 liquid alloy are presented, respectively. The most abundant structures in the U116Nb12 liquid alloy are those having HA indices of 1551, 1541, 1431, 1441 and 1661. The Voronoi analysis reveals that the distributions of local atomic structures at high temperature are homogeneous, whereas Voronoi polyhedra trend to form , , , , , and with the larger fraction at low temperature. The analysis of chemical short-range order and structural properties suggests that the icosahedra and bcc-type clusters play the dominant roles upon cooling and, the addition of Nb in the U116Nb12 liquid alloy is indeed beneficial to occurrence of the local atomic structural evolution.

Inorganic chalcogenides are traditional high-performance thermoelectric materials. However, they suffer from intrinsic brittleness and it is very difficult to obtain materials with both high thermoelectric ability and good flexibility. Here, we report a flexible thermoelectric material comprising highly ordered Bi2Te3 nanocrystals anchored on a single-walled carbon nanotube (SWCNT) network, where a crystallographic relationship exists between the Bi2Te3 < $$\bar{1}2\bar{1}0$$ > orientation and SWCNT bundle axis. This material has a power factor of ~1,600 μW m−1 K−2 at room temperature, decreasing to 1,100 μW m−1 K−2 at 473 K. With a low in-plane lattice thermal conductivity of 0.26 ± 0.03 W m−1 K−1, a maximum thermoelectric figure of merit (ZT) of 0.89 at room temperature is achieved, originating from a strong phonon scattering effect. The origin of the excellent flexibility and thermoelectric performance of the Bi2Te3–SWCNT material is attributed, by experimental and computational evidence, to its crystal orientation, interface and nanopore structure. Our results provide insight into the design and fabrication of high-performance flexible thermoelectric materials. Bi2Te3 materials suffer from brittleness, limiting their application for thermoelectric harvesting. By depositing ordered nanocrystals onto single-wall carbon nanotubes, a flexible material is formed that achieves ZT of 0.89 at room temperature.

The septuple-atomic-layer VSi2P4 with the same structure of experimentally synthesized MoSi2N4 is predicted to be a spin-gapless semiconductor (SGS) with the generalized gradient approximation (GGA). In this work, the biaxial strain is applied to tune the electronic properties of VSi2P4, and it spans a wide range of properties upon increasing the strain from a ferromagnetic metal (FMM) to SGS to a ferromagnetic semiconductor (FMS) to SGS to a ferromagnetic half-metal (FMHM). Due to broken inversion symmetry, the coexistence of ferromagnetism and piezoelectricity can be achieved in FMS VSi2P4 with the strain range of 0% to 4%. The calculated piezoelectric strain coefficients d11 for 1%, 2% and 3% strains are 4.61 pm V-1, 4.94 pm V-1 and 5.27 pm V-1, respectively, which are greater than or close to a typical value of 5 pm V-1 for bulk piezoelectric materials. Finally, similar to VSi2P4, the coexistence of piezoelectricity and ferromagnetism can be realized by strain in the VSi2N4 monolayer. Our works show that VSi2P4 in the FMS phase with intrinsic piezoelectric properties can have potential applications in spin electronic devices.