Phase Equilibria Studies of the Cu-Fe-O-Si System in Equilibrium with Air and with Metallic Copper

Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373?K and 1673?K (1100?°C and 1400?°C) and (2) with metallic copper at temperatures between 1373?K and 1573?K (1100?°C and 1300?°C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of ??Cu₂O??-??Fe₂O₃??-SiO₂ ternary sections. The relationships between the activity of CuO_0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems.     

Experimental Phase Equilibria Studies of the Pb-Fe-O System in Air,in Equilibrium with Metallic Lead and at Intermediate Oxygen Potentials

The phase equilibria information on the Pb-Fe-O system is of practical importance for the improvement of the existing thermodynamic database of lead-containing slag systems (Pb-Zn-Fe-Cu-Si-Ca-Al-Mg-O). Phase equilibria of the Pb-Fe-O system have been investigated: (a) in air at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); (b) in equilibrium with metallic lead at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); and (c) at intermediate oxidation conditions for the liquid slag in equilibrium with two solids (spinel + magnetoplumbite), at temperatures between 1093 K and 1373 K (820 °C and 1100 °C). The high-temperature equilibration/quenching/electron probe X-ray microanalysis technique has been used to accurately determine the compositions of the phases in equilibrium in the system. The Pb and Fe concentrations in the phases were determined directly; preliminary thermodynamic modeling with FactSage was used to estimate the ferrous-to-ferric ratios and to present the results in the ternary diagram.     

Feasibility study of the new rutile extraction process from natural ilmenite ore based on the oxidation reaction

Phase relations in the Fe₂O₃-FeTiO₃-TiO₂ system were investigated by equilibrating synthetic samples in evacuated sealed quartz tubes at a temperature of 1373 K. The equilibrium partial pressure of oxygen was measured by the electromotive force (EMF) method in the temperature range of 1273 to 1373 K. The phase diagram and oxygen partial pressure diagram in the titanium-iron-oxygen ternary system were then constructed at 1373 K. Rutile extraction from natural ilmenite ore was discussed from the thermodynamic viewpoint. It is found that rutile can be produced from common natural ilmenite ores not only by the reduction as the conventional titanium-rich slag process but also by an oxidation. Then, the oxidation experiment was conducted in air using Australian ilmenite ore to obtain rutile as one of the coexistent phases. Magnetic separation and leaching experiments for synthesized pseudobrookite and reagent rutile were conducted to confirm the possibility of separation of rutile from pseudobrookite. A new rutile extraction process was then proposed.     

Initial-stage Sintering Kinetics of Nanocrystalline Tungsten

Initial-stage sintering kinetics of nanocrystalline tungsten has been studied in the temperature range of 1273–1473 K (1000–1200 °C). Nanocrystalline tungsten sinters initially through a grain boundary diffusion mechanism. The calculated activation energy was 388 ± 11 kJ/mol at low temperatures (1273–1373 K (1000–1100 °C)) and 409 ± 7 kJ/mol at high temperatures (1373–1473 K (1100–1200 °C)), which are close to the experimentally measured activation energy for grain boundary diffusion (385 kJ/mol).     

A Comparison of Static and Cyclic Long-Term Oxidation of Two Nb-Cr-Mo-Si-B Alloys

Nb-25Cr-20Mo-15Si-10B (compositions in at pct) and Nb-25Cr-20Mo-15Si-15B alloys were exposed to air for a maximum period of 2 weeks under static and cyclic conditions to determine oxidation response. Oxidation was carried out at temperatures of 973 K, 1173 K, 1373 K, and 1573 K (700 °C, 900 °C, 1100 °C, and 1300 °C). Results of long-term cyclic oxidation show an increase in oxidation resistance with an increase in boron content. Pesting has been observed at 973 K (700 °C) in the 10B alloy in cyclic and static modes of oxidation. Comparative analysis of oxide formation is done by the weight gain per unit surface area method. The alloys and their oxides are characterized by X-ray diffraction, scanning electron microscopy, and X-ray mapping.     

High-Temperature Compression Behavior of Cast and Homogenized IN939 Superalloy

Hot deformation behavior of IN-939 superalloy was investigated in this work. Hot compression experiments were performed at temperatures of 1273 K, 1323 K, 1373 K, and 1423 K (1000 °C, 1050 °C, 1100 °C, and 1150 °C) at strain rates of 0.001, 0.01, 0.1, and 1 s^?1 up to a true strain of 0.8. Then variations in stress-strain curves as well as changes in microstructures of various hot-deformed samples were studied. At 1273 K to 1323 K (1000 °C to 1050 °C), dynamic recovery (DRV), and at 1373 K to 1423 K (1100 °C to 1150 °C), dynamic recrystallization (DRX), were recognized to be the main mechanisms of the alloy softening during hot compression tests. The relationships between flow stress, strain rate, and temperature were mathematically modeled with three well-known equations, and on the basis of those equations, the activation energy of hot deformation was calculated. For improvement of the proposed models, it was necessary to conduct the investigation at two temperature ranges: 1373 K to 1423 K (1100 °C to 1150 °C), in which DRX occurred, and 1273 K to 1323 K (1000 °C to 1050 °C), where DRV as well as γ′ precipitation happened. For each of the temperature ranges, a different value for activation energy was obtained, which in conjunction with the related model, can be used for simulating the deformation behavior of the alloy.     

Hot Deformation Behavior of As-Cast 2101 Grade Lean Duplex Stainless Steel and the Associated Changes in Microstructure and Crystallographic Texture

The hot deformation behavior of 2101 grade lean duplex stainless steel (DSS, containing ~5 wt pct Mn, ~0.2 wt pct N, and ~1.4 wt pct Ni) and associated microstructural changes within δ-ferrite and austenite (γ) phases were investigated by hot-compression testing in a GLEEBLE 3500 simulator over a range of deformation temperatures, T _def [1073 K to 1373 K (800 °C to 1100 °C)], and applied strains, ε (0.25 to 0.80), at a constant true strain rate of 1/s. The microstructural softening inside γ was dictated by discontinuous dynamic recrystallization (DDRX) at a higher T _def [1273 K to 1373 K (1000 °C to 1100 °C)], while the same was dictated by continuous dynamic recrystallization (CDRX) at a lower T _def (1173 K (900 °C)]. Dynamic recovery (DRV) and CDRX dominated the softening inside δ-ferrite at T _def ≥ 1173 K (900 °C). The dynamic recrystallization (DRX) inside δ and γ could not take place upon deformation at 1073 K (800 °C). The average flow stress level increased 2 to 3 times as the T _def dropped from 1273 to 1173 K (1000 °C to 900 °C) and finally to 1073 K (800 °C). The average microhardness values taken from δ-ferrite and γ regions of the deformed samples showed a different trend. At T _def of 1373 K (1100 °C), microhardness decreased with the increase in strain, while at T _def of 1173 K (900 °C), microhardness increased with the increase in strain. The microstructural changes and hardness variation within individual phases of hot-deformed samples are explained in view of the chemical composition of the steel and deformation parameters (T _def and ε).

     

KR脱硫渣的综合利用现状及其氧化去硫研究进展

KR脱硫的渣资源化利用有利于促进钢铁企业的绿色化发展.KR脱硫渣中主要成分为CaO,且含有质量分数为1.0％～2.5％的硫,直接将K R脱硫渣回用于冶炼工艺会导致钢液增硫.若能将渣中的硫脱出,可有效促进KR脱硫渣在钢铁冶炼工艺的资源化利用.因此,针对当前KR脱硫渣综合利用存在的问题,总结分析有关CaS氧化过程的热力学和...     

Deformation Behavior and Evolution of Microstructure and Texture During Hot Compression of AISI 304LN Stainless Steel

Deformation behavior of hot-rolled AISI 304 LN austenitic stainless steel was studied by hot axisymmetric compression tests at 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C) at strain rates of 0.01, 0.1, and 1 s^?1. The flow curves were examined to understand the deformation characteristics. The influence of Zener–Holloman parameter was analyzed using appropriate constitutive models. The activation energy for deformation was found to be 473 kJ/mol. Quantitative microstructural analysis was carried out using Electron backscattered diffraction. Compression at 1173 K (900 °C) at all true strain rates gave rise to partially dynamic recrystallized microstructure with strong α-fiber texture. The deformation texture is characterized by the formation of Brass component, and partial dynamic recrystallization (DRX) led to the development of Goss, S, and ube components. Necklace structure of small equiaxed recrystallized grains could be observed surrounding the large, elongated deformed grains. Compressions at 1273 K and 1373 K (1000 °C and 1100 °C) resulted in fully recrystallized microstructure consisting of mostly Σ3 and Σ9 coincidence site lattice high-angle boundaries. Compression at 1273 K (1000 °C) leads to the formation of low-intensity diffused α-fiber. DRX was confirmed by the presence of Goss, S, Cube, and rotated Cube components. Compression performed at 1373 K (1100 °C) resulted in nearly random texture with traces of α-fiber and prominent Cube/rotated Cube components. The microstructures of the 1173 K (900 °C)-compressed samples were partitioned using grain size and misorientation criteria to quantify DRX.     

Effect of Annealing on Properties of Carbonaceous Materials. Part II: Porosity and Pore Geometry

The pore structure of carbonaceous materials was studied using image analysis. The effect of annealing on the porosity and pore geometry of cokes, chars, and pyrolyzed coals (laboratory chars) was examined in the temperature range of 973 K to 1773 K (700 °C to 1500 °C). The porosity of chars and pyrolyzed coals significantly increased during annealing at temperatures below 1373 K (1100 °C) due to volatile matter release. Further increasing of the annealing temperature from 1373 K to 1773 K (1100 °C to 1500 °C) caused marginal porosity evolution. The porosity of cokes was not affected by annealing at temperatures below 1573 K (1300 °C) and slightly increased in the temperature range 1573 to 1773 K (1300 °C to 1500 °C). The increase in the porosity of chars and pyrolyzed coals during annealing at temperatures 1373 K to 1773 K (1100 °C to 1500 °C), and cokes at 1573 K to 1773 K (1300 °C to 1500 °C), was a result of reactions with oxides of their mineral phases. Annealing had a marginal effect on the pore shape (Feret ratio) of carbonaceous materials, but enlarged the pore size of chars and pyrolyzed coals and decreased their pore density.     

Thermodynamic Modeling of Metal Desulfurization with Boron-Containing Slags of the CaO–SiO<Subscript>2</Subscript>–MgO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript> System

In thermodynamic modeling of the desulfurization of steel by CaO–SiO₂–MgO–Al₂O₃–B₂O₃ slag on the basis of HSC 6.12 Chemistry software (Outokumpu), the influence of the temperature (1500–1700°C), the slag basicity (2–5), and the B₂O₃ content (1–4%)1 on the desulfurization is analyzed. It is found that the sulfur content is reduced with increase in the temperature from 1500 to 1700°C, within the given range of slag basicity. At 1600°C, the sulfur content in the metal is 0.0052% for slag of basicity 2; at 1650°C, by contrast, its content is 0.0048%. Increase in slag basicity from 2 to 5 improves the desulfurization, which increases from 80.7 to 98.7% at 1600°C. If the B₂O₃ content in the slag rises, desulfurization is impaired. At 1600°C, the sulfur content in the metal may be reduced to 0.0052 and 0.0098% when using slag of basicity 2 with 1 and 4% B₂O₃, respectively; in the same conditions but with slag of basicity 5, the corresponding values are 0.00036 and 0.00088%, respectively. Note that desulfurization is better for slag without B₂O₃. According to thermodynamic modeling, metal with 0.0039 and 0.00019% S is obtained at 1600°C when using slag of basicity 2 and 5, respectively, that contains no B₂O₃. The results obtained by thermodynamic modeling for the desulfurization of metal by CaO–SiO₂–MgO–Al₂O₃–B₂O₃ slag of basicity 2–5 in the range 1500–1700°C are consistent with experimental data and may be used in improving the desulfurization of steel by slag that contains boron.     

Microstructure,Mechanical and Abrasive Wear Behavior of 8.0 wt pct Cr White Iron Subjected to Continuous and Cyclic Annealing Treatment

Continuous annealing treatment (austenitization for 4 hours followed by furnace cooling) and cyclic annealing treatment (four cycles of austenitization, each of 0.66 hours duration followed by forced air cooling) of 8.0 wt pct Cr white iron samples are undertaken at 1173 K, 1223 K, 1273 K, 1323 K, and 1373 K (900 °C, 950 °C, 1000 °C, 1050 °C, and 1100 °C) as steps of destabilizing the as-cast structure. Continuous annealing results in precipitation of secondary carbides on a matrix containing mainly pearlite, while cyclic annealing treatment causes similar precipitation of secondary carbides on a matrix containing martensite plus retained austenite. On continuous annealing, the hardness falls below the as-cast value (HV 556), while after cyclic annealing treatment there is about 70 pct increase in hardness, i.e., up to HV 960. Decrease in hardness with increasing annealing temperature is quite common after both heat treatments. The as-cast notched impact toughness (4.0 J) is nearly doubled by increasing to 7.0 J after both continuous and cyclic annealing treatment at 1173 K and 1223 K (900 °C and 950 °C). Cyclic annealing treatment gives rise to a maximum notched impact toughness of 10.0 J at 1373 K (1100 °C). Abrasive wear resistance after continuous annealing treatment degrades exhibiting wear loss greater than that of the as-cast alloy. In contrast, samples with cyclic annealing treatment show reasonably good wear resistance, thereby superseding the wear performance of Ni-Hard IV.

     

Dynamic Recrystallization and Precipitation in 13Cr Super-Martensitic Stainless Steels

The influence of precipitation on the kinetics of static and dynamic recrystallization (DRX) was investigated in AISI 403 and 403Nb martensitic stainless steels. Hot compression tests were performed in the temperature range of 1073 K to 1473 K (800 °C to 1200 °C) and strain rates of 0.001 and 0.1 s^?1 to study DRX and precipitation behaviors. In parallel, stress relaxation tests were conducted with pre-strains of 0.1, 0.15, 0.2, and 0.25, a strain rate of 0.1 s^?1, and in the 1073 K to 1473 K (800 °C to 1200 °C) temperature range to study the kinetics of precipitation and recrystallization. Samples of hot compression and stress relaxation tests were quenched and the evolution of the microstructure was examined using optical and scanning electron microscopy. The results indicated that DRX interacts with dynamic precipitation (DP) over the temperature range of 1173 K to 1273 K (900 °C to 1000 °C). Hot compression testing results, confirmed by EBSD analysis, indicated that partial DRX occurs before precipitation in 403Nb, at 1073 K (800 °C). By contrast, no DRX was observed in 403 steel. At higher temperatures, i.e., over 1273 K (1000 °C), DRX preceded DP in both steels. Increasing the strain rate raised the temperature range of interaction between DRX and DP up to 1373 K (1100 °C). Strain-induced precipitation (SIP) was observed over the entire range of investigated test temperatures. Static recrystallization (SRX) took place predominantly in the temperature range of 1173 K to 1373 K (900 °C to 1100 °C), at which SIP significantly delayed the SRX finishing time. The results are analyzed in the framework of the classical nucleation theory and the underlying mechanisms are identified.     

Oxidation of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Scale-Forming MAX Phases in Turbine Environments

High temperature oxidation of alumina-forming MAX phases, Ti₂AlC and Cr₂AlC, were examined under turbine engine environments and coating configurations. Thermogravimetric furnace tests of Ti₂AlC showed a rapid initial transient due to non-protective TiO₂ growth. Subsequent well-behaved cubic kinetics for alumina scale growth were shown from 1273 K to 1673 K (1000 °C to 1400 °C). These possessed an activation energy of 335 kJ/mol, consistent with estimates of grain boundary diffusivity of oxygen (~375 kJ/mol). The durability of Ti₂AlC under combustion conditions was demonstrated by high pressure burner rig testing at 1373 K to 1573 K (1100 °C to 1300 °C). Here good stability and cubic kinetics also applied, but produced lower weight gains due to volatile TiO(OH)₂ formation in water vapor combustion gas. Excellent thermal stability was also shown for yttria-stabilized zirconia thermal barrier coatings deposited on Ti₂AlC substrates in 2500-hour furnace tests at 1373 K to 1573 K (1100 °C to 1300 °C). These sustained a record 35 µm of scale as compared to 7 μm observed at failure for typical superalloy systems. In contrast, scale and TBC spallation became prevalent on Cr₂AlC substrates above 1423 K (1150 °C). Cr₂AlC diffusion couples with superalloys exhibited good long-term mechanical/oxidative stability at 1073 K (800 °C), as would be needed for corrosion-resistant coatings. However, diffusion zones containing a NiAl-Cr₇C₃ matrix with MC and M₃B₂ particulates were commonly formed and became extensive at 1423 K (1150 °C).     

Microwave Absorption Characteristics of Conventionally Heated Nonstoichiometric Ferrous Oxide

The temperature dependence of the microwave absorption of conventionally heated nonstoichiometric ferrous oxide (Fe_0.925O) was characterized via the cavity perturbation technique between 294 K and 1373 K (21 °C and 1100 °C). The complex relative permittivity and permeability of the heated Fe_0.925O sample slightly change with temperature from 294 K to 473 K (21 °C to 200 °C). The dramatic variations of permittivity and permeability of the sample from 473 K to 823 K (200 °C to 550 °C) are partially attributed to the formation of magnetite (Fe₃O₄) and metal iron (Fe) from the thermal decomposition of Fe_0.925O, as confirmed by the high-temperature X-ray diffraction (HT-XRD). At higher temperatures up to 1373 K (1100 °C), it is found that Fe_0.925O regenerates and remains as a stable phase with high permittivity. Since the permittivity dominates the microwave absorption of Fe_0.925O above 823 K (550 °C), resulting in shallow microwave penetration depth (~0.11 and ~0.015 m at 915 and 2450 MHz, respectively), the regenerated nonstoichiometric ferrous oxide exhibits useful microwave absorption capability in the temperature range of 823 K to1373 K (550 °C to 1100 °C).     

Effect of Annealing on Properties of Carbonaceous Materials. Part III: Macro and Microstrengths

Carbonaceous materials including cokes, chars, and pyrolyzed coals were annealed at temperatures ranging from 973 K to 1773 K (700 °C to 1500 °C) in an inert atmosphere. Macro and microstrengths of original and annealed carbonaceous materials were characterized by the tensile strength and fracture toughness. Fracture toughness was determined for inert maceral-derived component (IMDC) and reactive maceral-derived component (RMDC) using ultramicro indentation. Experimental data obtained by tensile tests were processed using the Weibull statistical method to find “inherent” strength. Tensile strength of chars and coals was significantly increased by annealing at temperatures ranging from 973 K to 1373 K (700 °C to 1100 °C); further increase in annealing temperature to 1773 K (1500 °C) increased their tensile strength only slightly. Tensile strength of cokes decreased with the increasing annealing temperature; the major effect was observed in the temperature range from 1573 K to 1773 K (1300 °C to 1500 °C). Fracture toughness of chars and coals was enhanced significantly by heat treatment at temperatures ranging from 973 K to 1373 K (700 °C to 1100 °C) as a result of pyrolysis, while that of cokes increased slightly by heat treatment. Fracture toughness of IMDC was higher than RMDC. Macrostrength of carbonaceous materials was strongly affected by their porosity and microstrength. The effect of pore geometry on macrostrength was marginal. Decreasing the porosity was more effective compared with increasing the microstrength in improving the macrostrength of carbonaceous materials.     

Effect of Destabilizing Heat Treatment on Solid-State Phase Transformation in High-Chromium Cast Irons

This work describes the influence of secondary carbide precipitation at destabilizing heat treatment on kinetics of austenite phase transformation at a subcritical range of temperatures in high-Cr cast irons, alloyed with 4 to 6 wt pct of Mn or by complex Mn-Ni-Mo (Mn-Cu-Mo). The samples were soaked at 1073 K to 1373 K (800  °C to 1100  °C) (destabilization) or at 573 K to 973 K (300  °C to 700  °C) (subcritical treatment); the combination of destabilization and subcritical treatment was also used. The investigation was carried out with application of optical and electron microscopy and bulk hardness measurement. Time-temperature-transformation (TTT) curves of secondary carbide precipitation and pearlite transformation for as-cast austenite and destabilized austenite were built in this work. It was determined that the secondary carbide precipitation significantly inhibited the pearlite transformation rate at 823 K to 973 K (550  °C to 700  °C). The inhibition effect is more evident in cast irons alloyed with complex Mn-Ni-Mo or Mn-Cu-Mo. The possible reasons for transformation decelerating could be austenite chemical composition change (enriching by Ni, Si, and Cu, and depleting by Cr) and stresses induced by secondary carbide precipitation.     

Thermodynamic Simulation of the Influence of the Temperature and the Basicity of a Boron-Containing Slag on Steel Desulfurization

The results of thermodynamic simulation of the desulfurization of a medium-carbon steel by slags of the CaO–SiO₂–MgO–Al₂O₃–B₂O₃ system are presented. The HSC Chemistry 6.12 software package is used for the simulation. The thermodynamic simulation is performed for 20 various chemical compositions of slags with various B₂O₃ contents (1–4%)¹ and basicities ((CaO)/(SiO₂) = 2–5). The computations are performed using the Equilibrium Compositions module in the temperature range from 1500 to 1700°C with an increment of 50°C at a gas phase pressure of 0.1 MPa. The main results of the calculations are presented as the dependences of the change in the sulfur content in steel [S] on the temperature, the content of B₂O₃, and the slag basicity. An increase in the temperature of metal desulfurization from 1500 to 1700°C exerts a favorable effect on the sulfur content for the studied range of slag basicities. In particular, the sulfur content in steel decreases from 0.012 to 0.009% when steel is processed with the slag having 3% B₂O₃ and a basicity (CaO)/(SiO₂) = 2. A positive effect of an increase in the slag basicity from 2 to 5 on metal desulfurization is observed: the degree of desulfurization increases from 61.1 to 97.2% at 1600°C and 3% B₂O₃ content in the slag. As the B₂O₃ content in a slag increases from 1 to 4%, its refining properties decrease significantly in the range of basicity not higher than 2. In the range of high slag basicities (3–4), the negative effect of acidic oxide B₂O₃ on the refining properties of the slag decreases, providing low sulfur contents (which do not exceed [S] = 0.003–0.004% at 4% B₂O₃). At a slag basicity of 5, the sulfur content in steel decreases to 0.001%, all other things being equal. The simulation results can be used for the calculation of steel desulfurization processed by slags containing B₂O₃.     

Role of Heat Transfer in Early Stage Decarburization of DRI in Slag

The gas generation from reactions between direct reduced iron (DRI) pellets and steelmaking slags is known to take place in two stages; (1) the reaction of FeO and carbon within DRI, i.e., pellet internal reaction, followed by (2) the reduction of slag FeO with DRI carbon at the pellet?Cslag interface, if any carbon remains from the first step. To understand the controlling mechanism of the reaction between FeO and C inside DRI, the rate of the gas release and the temperature of pellets suspended in a slag-free atmosphere were quantified. The results were used to determine the apparent thermal conductivity of DRI that showed values of approximately 0.5 to 2 W.m^?1.K^?1 for a temperature range of 573?K to 1273?K (300?°C to 1000?°C). Furthermore, it was found that the experimental gas evolution rates are consistent with the values predicted by a heat?Ctransfer based model, confirming that the FeO-C reaction within pellet is controlled by the rate of heat transfer from the slag to the DRI pellet.     

Enhanced Sintering of TiNi Shape Memory Foams under Mg Vapor Atmosphere

TiNi alloy foams are promising candidates for biomaterials to be used as artificial orthopedic implant materials for bone replacement applications in biomedical sector. However, certain problems exist in their processing routes, such as formation of unwanted secondary intermetallic phases leading to brittleness and deterioration of shape memory and superelasticity characteristics; and the contamination during processing resulting in oxides and carbonitrides which affect mechanical properties negatively. Moreover, the eutectic reaction present in Ti-Ni binary system at 1391?K (1118?°C) prevents employment of higher sintering temperatures (and higher mechanical properties) even when equiatomic prealloyed powders are used because of Ni enrichment of TiNi matrix as a result of oxidation. It is essential to prevent oxidation of TiNi powders during processing for high-temperature (>1391?K i.e., 1118?°C) sintering practices. In the current study, magnesium powders were used as space holder material to produce TiNi foams with the porosities in the range of 40 to 65?pct. It has been found that magnesium prevents secondary phase formation and contamination. It also prevents liquid phase formation while enabling employment of higher sintering temperatures by two-step sintering processing: holding the sample at 1373?K (1100?°C) for 30?minutes, and subsequently sintering at temperatures higher than the eutectic temperature, 1391?K (1118?°C). By this procedure, magnesium may allow sintering up to temperatures close to the melting point of TiNi. TiNi foams produced with porosities in the range of 40 to 55?pct were found to be acceptable as implant materials in the light of their favorable mechanical properties.