رضا تقی آبادی

In this study the effect of grain refinement was studied on the hot tearing behavior of 3 wt. % Ce-modified 2024 Al alloy. Towards this end, different amounts of Ti (0.01, 0.02, and 0.05 wt. %) were added to the molten alloy through Al-5Ti-1B master alloy. According to the results, adding Ti marginally improved the fluidity length, relatively reduced the size shrinkage micropores, dispersed the micropores, reduced the grains size, and decreased the alloy hot tearing susceptibility (HTS). The addition of 0.01, 0.02, and 0.05 wt. % Ti decreased the alloy porosity content, grain size, and the HTS by 5, 20, 31%, 20, 75, 80%, and 9, 24, 34%, respectively. Based on the microstructural characterization and hot tear subsurfaces examination results, the relative improvement of hot tearing behavior can be explained by the refinement of grains and its positive consequences such as decreasing the liquid film thickness between the grains (which increases the capillary force and improves inter-grain feeding), increasing the alloy strength, decreasing the linear contraction, and decreasing the stress applied on grain boundaries as easy growth locations for the hot tear cracks.

In the current study the effect of mold mechanical vibration during the solidification was studied on microstructure and corrosion behavior of Zn-4Si composite. According to the microstructural observation results, mechanical vibration substantially improved the SiP particle distribution and refined them. The image analysis results showed that mechanical vibration at 20, 40, and 60 Hz reduced the average size of SiP particles by 34, 55, and 75%, and increased their number density by 6, 16, and 36 times, respectively. Mechanical vibration at the 20, 40, and 60 Hz also decreased the average grain size by 50, 68, and 76%, respectively and increased the equiaxed zone in castings. The results of Tafel and impedance corrosion tests at 3.5 wt. % NaCl solution implied on increasing the corrosion current and shifting the corrosion potential to the more negative values in mechanically vibrated samples. The corrosion current of as-cast and 60 Hz samples were determined as -1.3610-5 and -2.3310-5 A, respectively. Mechanical vibration also reduces the corrosion resistance of samples where the resistance of 60 Hz sample (about 76 ohm) is lower than that of as-cast sample by about 45%. The increased density of grain boundaries and fine distribution of primary Si particles (as cathodic points) in the composite matrix are characterized as the most important factors decreasing the corrosion resistance of the composite. This is because they increased the number and interspacing of the galvanic cells within the matrix and exhibited appropriate locations for pitting.

Achieving the desired mechanical properties in in-situ composites is governed by morphological modification, refinement, and even distribution of reinforcement particles which are formed during their solidification. This study was aimed to investigate the effect of Ti addition and multidirectional forging (MDF), as an industrially practical process, on microstructure and shear mechanical properties of cast ZA22-4Si composite. The obtained results showed that chemical modification of composite through 0.2 wt. % Ti addition converted the coarse primary grains to the well-refined equiaxed grains and reduced the size of primary Si particle (SiP), and porosities and improved their distribution within the matrix. The image analysis results also indicated that the average size of grains and SiP particles reduced from 750 and 25 mm to about 135 and 15 mm, respectively. Applying MDF at 100 ° C at the different passes breaks the primary dendrite network, decreased the average size of SiP particles, and promoted their even distribution within the matrix. According to the image analysis results in 2- and 5-pass MDFed composite the average size of SiP particles reached to about 8 and 6 μm, respectively. The shear punch tests also indicated that the combined effect of MDF and Ti addition reduced the strength whilst improved the ductility of as-cast composite where the yield and tensile shear strength of 5-pass MDFed sample reduced from 135 and 164 MPa to about 92 and 130 MPa, respectively, and its normal displacement value improved from 0.52 to about 0.72.

In this study the effect of mechanical vibration (20 Hz, 40 Hz, and 60 Hz) during solidification on microstructure, hardness, and dry sliding wear resistance of Zn-4Si composite was studied. According to the results, Si addition led to the formation of primary Si (SiP) and eutectic Si (SiE) in the microstructure. This increased the hardness of Zn matrix from 30 BHN to more than about 60 BHN. However, uneven distribution (agglomeration) of SiP particles resulted in uneven hardness within the composite matrix. Applying the mechanical vibration during the solidification of composite improved the SiP particle distribution and refines them. According to the pin-on-disk sliding wear results, at the applied pressures of 0.25, 0.5, and 0.75 MPa, the sliding wear resistance of the modified composite (at the 60 Hz frequency) is higher than that of the as-cast composite by 50, 60, and 65%, respectively. Moreover, at the applied pressure of 0.75 MPa the average friction coefficient of mechanically-vibrated composite (60 Hz) is lower than that of as-cast composite by about 23%. Based on worn surface and wear debris analyses the substantial improvement of wear resistance in modified composites can be attributed to the improved tribolayer stability due to the strengthening effect of hard Si particles on the substrate material.

In the current study the microstructure and mechanical properties of Al-2Ni-xMn alloys was investigated as a substitute for Al-4Ni alloys. To this end, different melts containing 2 wt. % Ni and 1, 2, and 4 wt. % Mn were solidified at two cooling rates of 3.5 and 10.4 C/s. According to the results, under the low solidification rate, the tensile strength, fracture strain, and toughness of Al-2Ni-1Mn alloy are lower than those of Al-4Ni alloy by 26, 115, and 137%, respectively. However, further Mn addition impaired the tensile properties. Increasing the solidification cooling rate decreases the size and improves the distribution of Ni(Mn)-rich compounds and porosities within the microstructure and reduces the sizes of secondary dendrite arm spacing and grains. This substantially improved the mechanical properties of Mn-rich alloys. For instance, compared to Al-4Ni alloy solidified at 3.5 C/s, the tensile strength, fracture strain, and toughness of copper mold cast Al-2Ni-1Mn alloy increased by 50, 200, and 330%, respectively.

This study was conducted to investigate the effect of Si addition (1, 2, 3, and 5 wt. %) on the microstructure and castability of hypoeutectic Al-4.5Cu-Si alloys. According to the results, Si addition increased the average size and volume fraction of eutectic Si platelets in the microstructure. Adding Si also improved the fluidity and decreased the porosity content of the alloy, and enhanced its resistance against hot tearing. According to the constrained rod test results, the hot tearing sensitivity index (HTS) of the alloys containing 1, 3, and 5 wt. % Si, was decreased by 48, 78, and 88%, respectively. In agreement with hot tearing testing results, the extensive existence of dendrites and shrinkage micropores on the hot torn surface of the alloy without Si implies on its low potential in feeding the solidification shrinkages and healing hot cracks. Adding Si decreased the amount of shrinkage micropores on the hot torn surface and due to improving the fluidity as well as increasing the amount of Al-Cu-Si ternary eutectic at the last stage of solidification, improved the feeding characteristics of alloy. Therefore, the amount of free dendrite arms was significantly decreased on the fracture surface. However, adding 5 wt. % Si increased the amount of eutectic Si on the hot torn surface giving rises to a more brittle fracture mode.

In this study, the effect of multidirectional forging (MDF) was studied on the microstructure and mechanical properties of Ti-modified SiP/ZA22 composite containing 4 and 8 wt. % Si. The forging process was performed at 100 °C by two and five passes. Based on the obtained results, Ti modification refined the coarse primary dendrites, and reduced the size of primary Si (SiP) particle as well as grains. Applying MDF also gradually eliminated the dendritic structure, promoted fine distribution of SiP particles, second phases, and porosities in the microstructure. According to the image analysis results, the average size of SiP particles in as-cast composite reduced from 25 and 30 μm to about 6 and 7 μm, respectively in 5-pass MDFed composites containing 4 and 8 wt. % Si. The mechanical properties results also showed work softening during the MDF where after two-pass MDF the hardness and tensile strength of the base sample reduced by 30 and 25%, while its elongation and toughness improved by 120 and 325%, respectively. In MDFed composites, the presence of SiP particles maintains the hardness and strength. According to the results, in the case of 2-pass MDFed composite containing 4 wt. % Si the hardness and tensile strength reduced by 18 and 2%, respectively, but the elongation and toughness increased by 25 and 175%, respectively.

This study was undertaken to improve the tensile properties of Al-4.5Cu-xSi-yFe alloy through thermal modification (T6 heat treatment). To this end, different amounts of Si (0.1-2.5 wt.%) and Fe (0.05-2.5 wt.%) were added to the alloy composition in order to investigate the effect of Fe/Si ratio on the alloy tensile properties and quality index in as-cast and heat treated conditions. According to the results, adding Si up to 2.5 wt.% improved the base (Fe-free) alloy fluidity. However, the maximum fluidity in Fe-bearing alloys obtained at 1.5 wt.% Si. The optimum Si content for maximum tensile strength and fracture strain in low-Fe alloys was determined as 1.5 and 0.5 wt.%, respectively. However, in Fe-containing alloys the optimum Si was determined based on the Fe/Si ratio. At the Fe/Si≤1 the compacted α-FeMn compound is the dominant Fe-phase which is not detrimental to the tensile properties. At the Fe/Si>1 the fraction of detrimental β-platelets is increased at the expense of α-FeMn. In as-cast condition, the maximum tensile strength and ductility are obtained in 1.5 wt.% Si containing alloy at the Fe/ Si ratio of unity and 0.3, respectively. Applying heat treatment encouraged the precipitation hardening as well as dissolution/ fragmentation of hard eutectic Si and Fe-rich platelets. Under this circumstance, the maximum tensile strength belongs to the sample containing 2.5 wt.% Si and Fe/Si ratio of unity where its tensile strength is higher than that of the as-cast and heat treated base alloy by 40 and 15%, respectively.

Joining of stainless steels to carbon steels is one of the most widely used types of dissimilar joints. In this research, the microstructure and mechanical properties of dissimilar shielded metal arc welding of austenitic stainless steel AISI 316L to carbon steel St-37 is studied. This joining has made by E316L electrode and three heat inputs of 0.72, 0.84 and 1.0 kJ/mm. The microstructure of the joints was characterized by optical and scanning electron microscopy. The mechanical properties of the joints were evaluated by tensile and microhardness tests. The solidification microstructure of the weld metals contained mainly austenite and some skeletal delta ferrite. There was an epitaxial growth at the interface of the weld metal with the AISI 316L steel HAZ, and at the interface of the weld metal with the St-37 HAZ, there is an un-etched narrow area which is suggested to have austenitic-martensitic structure. The results of hardness tests showed that the hardnessof the interface of the weld metal with the St-37 steel was maximum which is attributed to the formation of the martensitic narrow band. The longitudinal tensile results showed that the increasing of the heat input decreaes the tensile strength and increases the elongation of the joints.

Cast Al-15Mg2Si composites due to appropriate specific strength and tribological properties are ‎widely used in automotive and aerospace industries. The improved properties of these composites ‎are governed by the correct controlling of morphology, size, and distribution of primary Mg2Si ‎particles. In this study the effect of solidification cooling rate (chill modification) was investigated ‎on structure and quality index of Al-15Mg2Si composite. The casting operation was performed in ‎different molds with varying cooling rates of 2.7, 5.5, 17.1, and 57.5 °C/s. According to the ‎microstructural observation and image analysis results, increasing the solidification rate resulted in ‎refinement of primary Mg2Si particles and improvement of their distribution in the matrix. The ‎increased solidification cooling rate, moreover, refined the grains so that increasing cooling rate ‎from 2.7 to 57.5 °C/s resulted in 93% reduction in grain size. These microstructural variations ‎improved the composite tensile strength, fracture strain, and quality index. The quality index of ‎composite solidified at 2.7 °C/s was found to be lower than that of composite solidified at cooling ‎rate of 57.5 °C/s by 240%.

In this paper, the distribution of temperature and thermal cycle in gas tungsten arc welding of stainless steel 304 is studied. The welding operation was performed under different heat inputs of 540 and 782 kJ/mm on the plates with 2 mm thickness. The Abaqus software was employed for simulation. The volumetric heat distribution, according to the double ellipsoidal (Goldak) model, was considered as the heat source of the welding and DFLUX subroutine was coded by FORTRAN. The simulation results were compared with the Rosenthal and Adams models and experimental results. The simulation results with both heat inputs are well compatible with the cross section dimensions of the welds, while the Rosenthal model predicts a smaller welds’ pool size. The temperature-time curves obtained from the simulation and Rosenthal model have considerable differences but their predicted cooling time and rate in the temperature range of 800 to 500 °c, especially in heat input of 782 kJ/mm, are close to each other (the difference is less than 7.2%). The results also showed that the maximum temperature of the regions farther from the fusion boundary in Adams model is predicted higher than that of simulation and Rosenthal model, while the results of simulation and Rosenthal model are closer to each other.

In-situ Al-15Mg2Si composite due to their low density and good strength and wear properties are considered as potential candidates to substitute the Al and cast iron parts used in automotive and aerospace industries. The improved properties of these composites are governed by controlling the size and morphology (modification) of the primary Mg2Si particles. In the current study the effect of Cu addition (1.0, 3.0, and 5.0 wt. %) on metallurgical structure and quality index of Al-15Mg2Si composite was investigated. According to the results, Cu addition modified the morphology and reduced the average size of primary Mg2Si particles. The addition of Cu up to 3.0 wt. % improved the composite tensile strength by up to 34% whilst its further addition impaired the tensile properties. Moreover, the addition of Cu up to 1.0 wt. % improved the composite elongation by about 7%. This is while its further addition deteriorated the composite ductility. The maximum quality index was observed in 3.0 wt. % Cu containing composite where its quality index was 8% higher than that of the base sample. The microstructural observations, micro-hardness testing, precipitates chemical analysis, and fractography of fractured surfaces revealed that solid-solution-strengthening, dispersion hardening of Cu-containing precipitates, and modification of Mg2Si particles are the main factors improving the composite quality. Moreover, increasing the volume fraction of hard Cu-precipitates and micro-pores, negatively affected the composite tensile properties and quality index.

Hypoeutectic Al-Ni alloys are extensively used in automotive and aerospace industries due to their excellent castability and appropriate high-temperature specific strength. The addition of Mn to the composition of these alloys promotes the formation of Mn-rich precipitates and improves their strength and hardness, especially at high temperatures. However, if the Mn content exceeds 2 wt. %, increasing the size and volume fraction of Mn-rich compounds adversely affects the mechanical properties, especially the ductility and toughness of the alloys. On this basis, the current study was aimed to control the negative impact of high Mn content on tensile properties of hypoeutectic Al-Ni alloys by increasing the solidification rate and friction stir processing. For this purpose, the Al-4Ni-4Mn samples, prepared under different solidification rates of 3.5 and 10.4 °C/s, were subjected to friction stir processing (12 mm/min, 1600 rpm). Microstructural characterization and image analysis results show the substantial refinement of Mn-rich particles and their distribution in the matrix, refinement of grains, and elimination of casting defects such as gas/shrinkage porosities and entrained oxide bifilms. According to the results, increasing the solidification rate and applying of friction stir processing improved the tensile strength, yield strength, fracture strain, toughness, and microhardness of alloy by 63, 55, 123, 188 and 58%, respectively.

This research work has been carried out to study the effect of different Ca contents (0.5, 1.0, 1.5, 2.0 and 3.0) on the microstructure and porosity content of ZK60 alloys. The samples were examined by using optical and scanning electron microscopy (SEM) to evaluate the modification efficiency of the alloy with different Ca concentrations. The cast specimens were modified, homogenized and extruded at 350 °C at an extrusion ratio of 12:1. The experimental results showed that the addition of Ca brings about the precipitation of a new phase and refines the as-cast grains. It was also found that the presence of Ca at higher concentrations (>2 wt. %) results in the formation of hard Ca-rich intermetallics segregated in cell boundaries. Hot-extrusion was found to be powerful in breaking the eutectic network and changing the size and morphology of Ca-rich intermetallic phase. By applying the extrusion process and increasing Ca concentration (up to 2.0 wt. %), the porosity percentage decreased from 13.62% to 6.34% and 7.11% to 3.89% for ZK60 and ZK60+3%Ca alloys, respectively.

In this study, the effect of Ca, Sr, Mn, and Be on modification and quality index ‎improvement of A356 aluminum alloy containing 1.2 wt% Fe impurity was studied in as-‎cast and heat treated conditions. According to the results, Sr and Ca modified the eutectic Si ‎particles and decreased the size of detrimental β-Al5FeSi compounds so that their average ‎size reduced by 23 and 18%, respectively. The addition of Be and Mn did not affect the ‎eutectic Si, but converted the brittle b-platelets to the α-Fe Chinese-scripts. Due to this ‎microstructural variation, the quality index of the alloys modified by Ca, Sr, Be, and Mn has ‎increased by 58, 32, 31, and 17%, respectively. T6 heat treatment led to the precipitation ‎hardening of the alloy, thermally modified the eutectic Si particles, and fractured the b-‎particles. Although, it did not exert significant effect on the size and volume fraction of α-‎compounds. The maximum improvement of quality index in heat-treated samples (36 %) ‎was observed in non-modified base alloy whilst the amplitudes of the quality index ‎improvement in the Ca, Sr, Be and Mn modified samples were 6, 13, 21, and 19 ‎respectively. Increasing of porosity content and the remaining of rather large α-compounds ‎were found to be the most important factors responsible for the relative reduction of the ‎quality index in modified and heat treated samples.‎

The aim of current research was to examine the microstructure, mechanical properties and electrical conductivity of Al-7075 alloy that develops during Equal Channel Angular Pressing (ECAP) and Multi Directional Forging (MDF). The Annealed Al-7075 alloy was subjected up to 3 and 4 passes of MDF and ECAP deformation at room temperature, respectively. Followed by ECAP, Vickers microhardness and shear punch test were performed and microstructural observations were undertaken using transmission electron microscopy (TEM). The electrical conductivity was also measured by eddy current method. Microstructural investigations show that after 4 passes of ECAP very fine grains with average grain size of about 350 nm appear and most of the grains evolve into arrays of high angle boundaries. On the other hand, 3 passes of MDF leads to higher grain size (950 nm) and lower fraction of high angle boundaries compared with 4 pass of ECAP. Mechanical properties of specimens increase about 100 and 50 percent after 3 passes of MDF and 4 passes of ECAP, respectively. So, it can be concluded that the ECAP process is more effective than the MDF process in grain refinement and improvement of mechanical properties. The electrical conductivity measurement at room temperature showed that there was no significant change in the conductivity of the processed samples compared with the initial specimen. Finally, it can be deduced that grain refinement during ECAP and MDF processes can be considered as a strategy to improve mechanical strength of pure metals without sacrifice of their electrical conductivity.

The effect of Mn addition (2 and 4 wt%) on the microstructure and castability of hypoeutectic Al-2Ni alloy was investigated. According to the results, Mn promotes the formation of Mn(Ni)-rich intermetallics in the microstructure. In the case of Al-2Ni-2Mn alloy the intermetallic compounds are interdendritic type whilst in Al-2Ni-4Mn alloy in addition to interdendritic intermetallics, the large and primary Mn-rich compounds with platelets, polyhedral and dendritic morphologies are present. The fluidity results show that the addition of 2 and 4 wt% Mn enhances the mushy solidification of Al-2Ni alloy leading to a fluidity reduction of 7 and 30%, respectively. Based on the microstructural observations and thermal analysis results, this reduction can be attributed to the formation of primary Mn-rich compounds in the molten alloy. Manganese addition, also, exerts negative impact on the hot tearing resistance of Al-2Ni alloy. The hot tearing susceptibility index (HTS) of Al-2Ni-4Mn alloy is 5 and 12 times higher when compared to those of Al-2Ni-2Mn and Al-2Ni alloys, respectively. SEM investigation of hot teared microcracks and the presence of free dendrites and primary Mn-rich compounds on the fractured surfaces imply on the critical role of primary compounds on the formation of hot tear microcracks.

Friction stir processing as a relatively new and effective solid-state process is used for surface modification of metals and alloys in order to modify their microstructure and properties. In this study, the effect of friction stir processing on the microstructure and mechanical properties of an Al-0.9Ni-Fe alloy was investigated. The process was performed under the rotational speeds of 600-2000 rpm and the traverse speed of 25 mm/min. According to the results, the severe surface plastic deformation refined the intermetallic compounds present in the microstructure, improved their distribution within the matrix, and substantially reduced the amount of casting defects. As a result of these microstructural variations, the tensile strength and percent elongation of the base alloy are increased by almost 40 and 205%, respectively. The fracture toughness is also improved by 205%. It was also found that the hardness of processed alloy is about 24% higher as compared to the base alloy.

In this study, the effect of Cu addition (0.5, 1.0 and 1.5 wt%) and T6 heat treatment on the tensile properties and quality index of A356 alloy containing different amount of iron (0.5-1.5 wt%) was investigated. According to the results in as-cast condition, the addition of copper to the iron bearing alloys increased the tensile strength by about 25% while substantially decreased the percent elongation (by almost 80%). After heat treatment, however, the tensile strength and the quality index of the alloy containing 1 wt% copper and 1.5 wt% iron were found to be increased by about 100 and 35% as compared to the base alloy, respectively. The improvement in the quality index was attributed to the precipitation hardening effect of Al2Cu and Mg2Si precipitates as well as thermal modification of eutectic silicon and iron-rich platelets, which increase the tensile strength, and ductility of the alloy.

The effect of Fe addition (0.5, 1, 1.5 and 2 wt %) and Mn modification (Mn/Fe=0.5) on hot tearing behavior of F332 Al alloys was investigated. The results show that due to the formation of fine interdendritic -Al5FeSi platelets, Fe addition up to 0.5 wt% improves high temperature tensile properties and promotes the formation of equiaxed grains thereby increases the hot tearing resistance of the alloy by about 25%. Further addition of Fe up to 2 wt%, however, increases the size and volume fraction of -platelets, decreases the tensile properties, reduces the fluidity and interdendritic feeding and consequently substantially increases the hot tearing susceptibility (HTS). Mn addition, however, was shown that changes the morphology of -platelets to less harmful Chinese script, polyhedral or star-like α-Al15(Fe,Mn)3Si2 whereby improves the tensile properties and interdendritic feeding characteristic of the alloy. Therefore, the HTS value is decreased to zero for 0.5 and 1 wt% Fe alloys, but increased by 50 and 40 %, respectively in the case of 1.5 and 2 wt% Fe containing alloys.

In current study, effect of different content of calcium on the microstructure and mechanical properties of commercial ZK60 alloy is investigated. Micrographs of as-cast alloys were observed by optical and SEM microscopy. Experimental results show that the calcium addition was to be active in the refining of the grains of as-cast specimens by use of GRF mechanism. The tensile properties of the alloys increased from 149 to 220 MPa for base and ZK60%Ca alloy. Evaluation of the fracture surface of the base alloy showed that the modification process by calcium up to 3 percent change the ductile mechanisms of failure, to brittle mode.

The effect of iron (0.2 to 2 wt%) on the hot tearing susceptibility of Al-5Si and Al-9Si alloys was investigated. According to the results, addition of iron up to the 2 wt% improved hot tearing resistance of Al-5Si alloy and decreased its HTS by about 100%. This improvement was assumed to be mainly due to the fine and interdendritic distribution of Fe-rich intermetallic compounds. In the case of Al-9Si alloy however, despite of the lower solidification range and higher fluidity, addition of iron up to 2 wt% deteriorate hot tearing resistance. The HTS index was increased continuously by three times. Microscopic examination of the hot tear cracks reveals the precipitation of higher amounts of -Al5FeSi in interdendritic regions which adversely affect the tensile strength and elongation as well as blockage the interdendritic feeding channels thereby decrease the hot tearing resistance.

The Effect of Fe addition (0.2-2wt%) on the wear behavior of Al-(5-13)Si alloys was investigated. The pin-on-disk wear tests were conducted at room temperature, under normal load of 45N, sliding speed of 0.13 m/s for sliding distance of 1000m. The results showed that bellow a critical Fe content (1.2wt% in this research), Si addition improved the wear resistance. In this regard, the wear rate of Al-13Si-0.8Fe alloy was observed to be less than 50% of Al-5Si-0.8Fe. This could be attributed to the fine distribution of hard AlFeSi platelets in interdendritic regions that increased the hardness and decreased the subsurface deformation and asperities adhesion. So, controlled delamination within tribolayer as well as abrasive wear could be proposed as the main wear mechanisms. Formation of large primary AlFeSi platelets at the iron content of more than critical value, however, facilitates the initiation and propagation of subsurface cracks and instability of tribolayer. This led to the higher delamination and abrasive wear with higher Si containing alloys.

In the present study، the effects of iron and manganese on the tribological behavior of F332 alloy were investigated. Alloys with addition of 0. 7، 1. 2 and 1. 8wt% iron to the base alloy were prepared. The modification of the alloys was performed by proper additions of manganese. The pin-on-disk wear tests were carried out at room temperature under normal loads of 20، 30، 40، and 80 N، and sliding speed of 0. 5 m/s for sliding distance of 1000m. The results showed that the size and morphology of the iron-rich compounds greatly influenced the tribological behavior of the alloy. In the case of un-modified alloys، the alloy containing 0. 7wt% Fe، showed the best tribological and mechanical properties. Addition of higher amounts of Fe led to the formation of coarse، plate-like intermetallic compounds and، therefore، a considerable decrease in the wear resistance. The modification by manganese improved the tribological properties of the alloys and the highest wear resistance was obtained with the alloy containing 1. 8 wt% Fe.