Strain-induced Melt Activation Research Articles

Microstructure Evolution and Tensile Properties of In Situ TiB2(p)/Al-Cu Composite Processed by Modified Strain-Induced Melt Activation Method with Equal Channel Angular Pressing Pre-deformation

Microstructure Evolution and Tensile Properties of In Situ TiB2(p)/Al-Cu Composite Processed by Modified Strain-Induced Melt Activation Method with Equal Channel Angular Pressing Pre-deformation

Microstructure evolution and properties of semi-solid Al80Mg5Li5Zn5Cu5 light weight high entropy alloy prepared by SIMA

The semi-solid Al80Mg5Li5Zn5Cu5 light weight high entropy alloys were prepared by strain induced melting activation method (SIMA), and the microstructure evolution, mechanical properties and corrosion resistance of semi-solid Al80Mg5Li5Zn5Cu5 light weight high entropy alloys were investigated. The results indicate that the ideal globular or near-globular microstructures with an average grain size of 29.1 μm and a shape factor of 0.86 can be obtained when the Al80Mg5Li5Zn5Cu5 light weight high entropy alloys with 20% deformation held at 500 °C for 15 min. The coarsening coefficient is 35.8 μm3/s when the temperature is 500 °C, which is lower than the traditional single major element alloys due to the sluggish diffusion effect of high entropy alloys. The compression strength of semi-solid Al80Mg5Li5Zn5Cu5 light weight high entropy alloys is 558.4 MPa, which is 11% higher than that of as-cast state. The corrosion resistance of semi-solid Al80Mg5Li5Zn5Cu5 light weight high entropy alloys is also significantly improved.

The effect of Cu–8%P master alloy, SIMA process, thixoforming, and heat treatment on the microstructure and mechanical properties of Al–20%Mg2Si composite

In the present research, the effect of thixoforming and age-hardening heat treatment on the microstructure and mechanical properties of un-modified and modified Al–20%Mg2Si composites produced through the strain-induced melt activation (SIMA) process has been investigated. This method showed promising potential for manufacturing the ideal microstructure, achieving globular grains, and enhancing mechanical properties. Quantitative analysis has revealed that adjusting the semi-solid heat treatment parameters to a temperature of 570 °C and a holding time of 25 min optimizes the globular α-Al grains and Mg2Si particles, achieving the size of 20.62 μm and 66.71 μm and the shape factor of 0.81 and 0.83 for Mg2Si particles and α-Al grains, respectively. The yield strength of the modified Al–20%Mg2Si composite increased by 23.67% and the ultimate tensile strength increased by 21.20%, compared to the un-modified specimen. Both composites underwent the thixoforming process, illustrating the ultimate tensile strength and elongation of 93.68 MPa and 4.32% for the original composite and 138.86 MPa and 7.29% for the modified composite. The modified Al–20%Mg2Si composite was subjected to the effective combination of thixoforming and age-hardening. According to the tensile test results, the yield strength, ultimate tensile strength, elongation, and toughness raised by 138.72%, 140.92%, 267.70%, and 471.12%, respectively, compared to the as-cast specimen. Moreover, its impressive hardness of 125.1HB contributes to its overall performance.

Effect of cross-sectional reduction ratio on microstructure evolution of semi-solid 7075 aluminum alloy prepared by RFSIMA process

Semi-solid billets of 7075 aluminum alloy were fabricated by radial forging strain induced melting activation (RFSIMA) process. Effect of the cross-sectional reduction ratio on microstructure of fabricated 7075 aluminum alloys was analyzed. The results indicate that the average grain size of α-Al decreased from 109μm to 70μm as the cross-sectional reduction ratio increased from 0% to 73% during the 20-minute isothermal treatment at 620°C.The spheroidization trend of the grains became more pronounced; During the semi-solid isothermal treatment, the segregation of Cu at grain boundaries increased slowly with the increase in the cross-sectional reduction ratio. Zn and Mg exhibited uniform distribution without significant segregation at low cross-sectional reduction ratios (43% and below). When the cross-sectional reduction ratio reached 62%, slight segregation of Zn and Mg was observed at the grain boundaries. At a cross-sectional reduction ratio of 73%, the segregation of Zn and Mg at the grain boundaries reached a level similar to that of Cu. The optimal cross-sectional reduction ratio for the RFSIMA process was found to be 62%; the microstructural evolution mechanism of the semi-solid 7075 aluminum alloy prepared by the RFSIMA process was investigated.

An Application of Injection Molding to Semisolid Processing of Metallic Alloys: A Role of SIMA in Feedstock Transformation

Injection molding has proven for over 150 years to be the efficient mass manufacturing technology of net-shape components from plastics, however, its application to metallic alloys, despite four decades of commercialization, still creates challenges. Although early designs assumed a direct replacement of plastic with magnesium, subsequent research revealed essential differences in machinery and processing requirements, imposed by metallic alloys. The key discovery revealed that the dendrite-to-globule transformation during coarse particulate melting is caused by strain induced melt activation (SIMA) due to feedstock deformation imposed at their manufacturing stage, not due to the injection screw shearing during processing. As a result, the process control parameters and the screw and barrel design can be optimized with a focus on other screw functions. That discovery also led to the simplified machinery designs, eliminating the complex injection screw, and replacing it with a simple plunger.

Effect of strain-induced melt activation process and thixoforming on microstructure and mechanical properties of 319 aluminum alloy

The effect of the thixoforming process on the microstructure and mechanical properties of modified and grain refined 319 aluminum alloy has been investigated. The strain-induced melt activated (SIMA) process has been applied to achieve proper microstructure for semi-solid processing. As-cast 319 aluminum parts have a dendritic microstructure and mostly contain defects such as porosity and shrinkage. The semi-solid treatment process eliminates these defects and is used to obtain a spherical structure with enhanced mechanical properties. Image analysis of the semi-solid treated specimens showed that the best sample had the highest amount of α-Al particle sphericity (0.88) and the lowest average equivalent diameter of α-Al phases (56 µm) under the conditions of 30% of the hot pre-deformation at 560 °C and isothermal holding time of 30 min. The specimens were thixoformed after the SIMA process to generate near-net-shape pieces. The thixoforming process enhanced the hardness of 319 aluminum alloy from 78.1 ± 1.91 HB to 115.6 ± 1.73 HB. Based on the tensile test results, the thixoforming process raised the ultimate tensile strength, yield strength, elongation, and toughness by 30%, 69%, 180.5%, and 189%, respectively, compared to the as-cast state.

Influence of strain induced melt activation (SIMA) on the morphology of primary phase in steel microstructure

Strain induced melt activation (SIMA) is the mechanism for the formation of the globular microstructure under the controlled working process followed by holding the specimen at a temperature between solidus & liquidus pertaining to the given alloy system. The effect of SIMA process on the microstructure of steel, 10% and 15% deformed at 900°C and holding at 1400°C for 3 and 5 min separately were investigated. The metallographic examination of the SIMA processed steel was done and compared with the as received steel. It was observed that SIMA processed steel shows the globular structure as compared with the unprocessed steel. It was also found that as the deformation percentage increases, more globular structure forms. Due to the globular microstructure, there is enhancement in the mechanical properties such as tensile strength and hardness. The parameter such as degree of warm working process, temperature and holding time are important factor in controlling SIMA process. During mechanical working in the SIMA process, strain energy gets stored in the material. The 15% deformation with 3 min holding time enhanced the hardness and ultimate tensile strength by approximately 8% respectively as compared with as received sample. This acts as a driving force for recrystallization of warm worked steel which resulted in equiaxed grains of primary phase in the microstructure.

Thermal effect of quench rate on mechanical properties of SIMA 7075-T6

In this study, thermal effects of quench rate on mechanical properties of 7075-T6 alloy fabricated by strain induced melt activation (SIMA) process were investigated. The T6 heat treatments were applied in various parameters after SIMA: solutionizing at 490?C for 15-30-45-60-120 minutes, quenching at 60-100?C, and aging at 120?C for 12-24-48 hours. Optical and SEM analyses were performed for characterization, hardness, and tensile tests for mechanical evaluation. Analysis of variance tests was carried out to indicate the validity of the interactions quenching temperatures and tensile properties. Secondary phases were dissolved homogeneously after solutionizing but at higher quenching temperatures and reprecipitated, particularly at grain boundaries. Strength values decreased with increasing quenching temperature. Analysis of variance tests suggest that cryogenic quenching can further increase the tensile properties. Oxide bifilms, porosities, low surface quality, and continuous brittle secondary phases surrounding spheroidal particles reduce the mechanical properties.

The microstructure evolution of Al-5Ce alloy prepared by strain-induced melt activation during semi-solid isothermal treatment process

The coarse grains and rough eutectic microstructure of Al-Ce alloy seriously damage its performance. In this study, Al-5Ce alloys with fine eutectic fibers and bimodal grain distribution were fabricated by strain-induced melt activation (SIMA) process. The results demonstrated that with increasing isothermal temperature and soaking time, the Al11Ce3 phase changes from coarsening to remelting and the α-Al grains size decreases due to decomposition by liquid droplets during the semisolid isothermal treatment. And during the subsequent quenching process, the high cooling rate leads to the solidification of fine α-Al grains and the refinement of eutectic fibers and fiber spacing when the Al concentration exceeds the upper limit of eutectic composition, which forms bimodal grains with fine eutectic fibers.

Evaluation of microstructure and mechanical properties of M-SIMA processed Al–7Si alloy

In this research article, the effect of the strain-induced melt activation (SIMA) process on the microstructure and mechanical properties of the Al–7Si alloy has been investigated. The morphology of α-Al grains is changed from dendritic to fine spherical and flaky type eutectic Si to a fine fibrous eutectic Si after the modified strain-induced melt activation (M-SIMA) process. The intermetallic compounds are refined and distributed uniformly throughout the matrix after the M-SIMA process. The mechanical properties have been improved due to fine spherical grain formation with refined eutectic Si. A high tensile strength (UTS: 204 MPa) with a remarkable improvement in ductility (El: 30%) is achieved after the M-SIMA process at 585°C for 30 min in comparison to the as-cast Al–7Si alloy (UTS: 117 MPa, El: 16%).

Effect of Strain Induced Melt Activation Process on the Microstructure and Mechanical Properties of Al-5Ti-1B Treated Al-7Si Alloy

Effect of Strain Induced Melt Activation Process on the Microstructure and Mechanical Properties of Al-5Ti-1B Treated Al-7Si Alloy

The Effect of CRITSIMA Process Parameters on the Microstructure Evolution and Element Segregation of Semi-Solid CuSn10P1 Alloy Billet

In this paper, based on the as-cast CuSn10P1 alloy. Semi-solid CuSn10P1 alloy billet was prepared by cold-rolled isothermal treatment strain-induced melting activation (CRITSIMA). The effects of cold-rolling reduction, isothermal temperature, and isothermal time on the microstructure of semi-solid copper alloy billet were studied by metallographic microscope and Image-Pro Plus software. The changes of primary elements in as-cast and semi-solid microstructure were analyzed briefly by a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The results show that with the increase of cold rolling reduction, the average grain diameter of semi-solid microstructure decreases gradually, the average grain roundness increases first and then decreases, and the liquid fraction of the microstructure remains unchanged. During semi-solid isothermal treatment, with the increase of isothermal temperature and the extension of isothermal time, the average grain diameter increases gradually, the average grain roundness increases first and then decreases, and the liquid fraction increases gradually. When cold rolling reduction is 30%, isothermal temperature is 900 ℃, and isothermal time is 20 min, a better microstructure can be obtained. The average grain diameter, average grain roundness, and liquid fraction of semi-solid alloy billet are 66.45 μm, 0.71, and 12.78%, respectively. Sn and P diffuse from the intergranular liquid to the grain inside during the isothermal treatment from as-cast to semi-solid.

Effect of thixoforming and precipitation hardening on microstructure and mechanical properties of Al-10.5Si–3Cu-0.2Mg alloy produced by strain induced melt activation process

The effects of the thixoforming and the precipitation hardening heat treatment on the microstructure and mechanical properties of Al-10.5Si–3Cu-0.2Mg alloy produced by the strain-induced melt activation (SIMA) process have been investigated. According to previous researches of authors, new introduced alloy has superior mechanical properties in addition to good response to aging process compared with the casting aluminum alloys. The results of the image analysis showed that by increasing the deformation from 10% to 20% and the time of semi-solid heat treatment from 10 to 20 min, the best globular structure of α(Al) grains with the grain size and shape factor of 65 μm and 0.81 were obtained at 15 min for 20% pre-deformation, respectively. The thixoforming process increased the ultimate tensile strength of the alloy about 29%, the yield strength about 37% and the elongation about 6%, compared to the as cast condition. The 20% pre-deformed sample experienced precipitation hardening heat treatment in addition to thixoforming had the best mechanical properties having UTS, YS, elongation and hardness of 423 MPa, 331 MPa, 4.41%, and 144.24 BHN, respectively. Thixoforming plus precipitation hardening is an effective procedure to produce a particular microstructure in Al–Si–Cu–Mg system exhibiting the excellent castability and high mechanical properties.

Effects of strain-induced melt activation treatment on the microstructure and properties of Zn sacrificial anodes

Effects of strain-induced melt activation treatment on the microstructure and properties of Zn sacrificial anodes

Effect of compression ratio on microstructure evolution of Mg–10%Al–1%Zn–1%Si alloy prepared by SIMA process

A new Mg–10%Al–1%Zn–1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation (SIMA) process. The effect of compression ratio on the evolution of semisolid microstructure of the experimental alloy was investigated. The results indicate that the average size of α-Mg grains decreases and spheroidizing tendency becomes more obvious with the compression ratios increasing from 0 to 40%. In addition, the eutectic Mg2Si phase in the Mg–10%Al–1%Zn–1%Si alloy transforms completely from the initial fishbone shape to globular shape by SIMA process. With the increasing of compression ratio, the morphology and average size of Mg2Si phases do not change obviously. The morphology modification mechanism of Mg2Si phase in Mg–10%Al–1%Zn– 1%Si alloy by SIMA process was also studied.

Microstructural evolution of Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy prepared by strain-induced melt activation process

The semisolid billets of Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy were prepared by the strain-induced melt activation (SIMA) route, and the effects of isothermal heating parameters on the morphology and coarsening kinetics of primary solid grains were studied. It was found that the average grain size increased with the increase of isothermal time while the grain size showed different changing laws with the temperature at different isothermal times. The growth behavior of the primary solid grains was predominantly governed by the Ostwald ripening mechanism, although there is coalescence mechanism in some cases. As the isothermal temperature increased from 550 °C to 590 °C, the coarsening rate constant increased continuously and then declined when the temperature was further increased to 610 °C. Compared with other SIMA processed magnesium alloys, the present alloy showed a significantly lower grain coarsening rate constant due to the inhibiting effect of rare earth (RE) elements on coarsening. This research has provided an insight into the microstructural evolution of Mg-RE alloy under different heating conditions, and will provide valuable information for potential industrial applications.

In Situ Observation of Deformation-Induced Spherical Grains in Semi-Solid State of C5191 Copper Alloy.

The formation mechanism of spherical grains during the strain-induced melt activation is investigated by in situ observation of the cold rotary swaged materials during heat treatment. The microstructure of the cold rotary swaged material changed from original dendritic structure to spherical grains after heating semi-solid state, whereas the as-received alloy without deformation exhibited non-spherical grains. These results show that static recrystallization, preferential melting of grain boundaries, and small grains cause the deformed grains to form the initial spherical grain structure during the temperature rising to semi-solid state; besides, the Zener pinning effect of second-phase particle and the heterogeneous nucleation of solidification also play negative roles in spherical grain growth up freely during the cooling process.

Effect of isothermal process parameters on semi-solid microstructure of chip-based Al–Cu–Mn–Ti alloy prepared by SIMA method

A typical Al–Cu–Mn–Ti aluminum alloy chip was adopted to prepare semi-solid billets by a Strain-Induced Melt Activation (SIMA) method, and the effects of isothermal process parameters on the semi-solid microstructure evolution of the alloy were investigated in this work. The result showed that semi-solid billets with highly spheroidal and homogeneous fine grains could be prepared from chips by the SIMA method. With the increase of isothermal temperature, the finer and near-spherical grains are obtained, the grains coarsen and became ellipse at 903 K because of the coarsening mechanisms of coalescence and Ostwald ripening. The relationship of isothermal holding time and grains size followed the LSW theory well, and more spherical microstructure can be brought by prolonging the holding time until 3000 s. Thus, the optimal isothermal treatment temperature is 893 K and holding time is 3000 s, the corresponding average size and roundness of grains are 137 [Formula: see text]m and 1.108, respectively.

Strain induced melt activation (SIMA): original concept, its impact and present understanding

ABSTRACT The concept of converting dendritic structures into globular morphologies through solid-state deformation, termed as strain-induced melt activation (SIMA), is assessed. Although the original invention defined the specific two-stage deformation scenario, almost four decades of extensive research, involving a variety of ferrous and non-ferrous alloys, subjected to conventional and severe plastic deformations, caused its evolution. According to present understanding, any deformation of cast structures with a strain level sufficient to trigger recrystallisation leads to dendrite-to-globule transition during subsequent partial melting. It is proposed that the SIMA term should not only be associated with the particular deformation scenario but should be seen as a broad synonym for a variety of thermomechanical treatments, explored for controlling the solidification microstructure. Such an updated definition expands applicability of the SIMA concept from bulk billets to coarse particulates and fine powders.

Effect of compression deformation on the distortion energy and semi-solid microstructure of Mg-6Al-0.9Gd alloys

In order to investigate the effect of distortion energy on the microstructure of magnesium alloys prepared by strain induced melt activation (SIMA) process and partial remelting, Mg-6Al-0.9Gd magnesium alloys were deformed at 200 °C with 0-20% compression ratios, and the relationship between deformation and eutectic melting activation energy was established based on differential scanning calorimetry (DSC) analysis, thereby determining the distortion energy at different compression ratios. The results showed that distortion energy increased with increasing compression ratio, which contributed to the morphological transition from dentrictic to equiaxed structure, and accelerated the formation of liquid phase during subsequent partial remelting. All things (grain size, liquid fraction and distribution in the semi-solid microstructure) considered, the optimal compression ratio for this paper was 20%.