سعید احمدی فرد

The present study aims at critiquing the validity of the Savor of Divine Law (Maẕāq-i Sharīʿat.) in deducing Islamic rulings. It is conducted using the descriptive-analytical method with a critical approach, and information and data have been collected through library research.The Savor of Divine Law (Maẕāq-i Sharīʿat) is an intermediary between jurisprudential and ijtihādī reasons; meaning that when the jurist cannot find a general or specific reason for jurisprudential issues, he turns to this rule before deducing from various sources across legal branches. By relying on this as a speculative proof (ʾamara-yi ẓannī) in different issues, the jurist discovers the corresponding ruling. This study illustrates that various arguments have been cited to assert the validity of this rule as a source for deducing Islamic rulings. These include Sīra-yi ʿuqalāʾ (life of the wise), ʾiṭmīnān (assuredness), milāk-i ḥujjīyat-i khabar-i vāḥid (the validity of single information), istishmām az rivāyāt, and referring to deduction (istiqrāʾ). Analysis shows that all the aforementioned arguments are subject to critique and rejection, and the validity of Maẕāq-i Sharīʿat is disputable as a source for deducing Islamic rulings. Therefore, it is ruled as invalid.

For a long time, there has been a debate among experts and thinkers about whether or not a branch of science should have a subject. Legal theorists (Uṣūlī), like logicians and philosophers, have expressed their thoughts in this field. The late Ᾱkhund al-Khurasānī is one of the great scholars of science who has given his opinion taking the issue of having any scientific discipline as an evident and indisputable matter. According to what has been attributed to him, he has used the "Axiom of the One Effect" (qāʿida al-wāḥid maʿlūlī) as a proof of his claim. An examination of other experts' opinions also points to the two reasons, namely "the distinction of sciences" and "division of sciences into real and mentallyposited" (iʿtibārī) along with the "Axiom of the One Effect" as the evidence for the necessity of each science having a subject. The late Ᾱkhund al-Khurasānī not only maintains that every science should have a subject but he also says that the subject should be single and allencompassing. All three reasons can be criticized. According to the author, subject refers to a certain matter and it does not mean that subject should be single and encompassing. In other words, it is not necessary that the subject-matters of the issues be essentially united with each other or that they should form a single entity. It is enough to have a form of relationship. In other words, there need to be an abstract common axis with which the issues are related.

The A356 is a cast alloy which consist of aluminum, silicon and magnesium. This alloy has good strangth and ductility with excellent casting properties, high corrosion resistance and good fluidity. This alloy is wiedly used in the automotive industry, aircraft, defense industry and especially the automotive industry as a substitution of steel components. Poor wear resistance of the alloys is major limitation for their use. Friction stir processing (FSP) is a recognized surfacing technique as it overcomes the problems of fusion route surface modification methods. In this study, friction stir processing was utilized to incorporate TiO2 and graphite particles into the matrix of an A356 alloy to form surface hybrid nanocomposite. For fabrication of nanocomposite a constant tool rotation rate of 900 rpm and travel speed of 60 mm/min with a tool tilt angle of 3 degree was used. Keeping in view of the requirement for improving wear resistance of A356 alloy, friction stir processing was attempted for surface modification with TiO2 and graphite powders. SEM, metallography, hardness, nanoindentation and pin-on-disc wear testing were used for characterizing the surface of nanocomposite. Microstructural analysis showed a uniform distribution of reinforcement particles inside the nugget zone. The surface nanocomposite results in enhanced properties in mechanical properties and wear resistance compared to the behavior of the base metal. Addition of solid lubricant graphite improve tribological properties of the nanocomposite.

In this study friction stir welding was used to perform butt joint of Al5083 and simultaneous production of Al-ZrO2 nanocomposite in weldment. Welding parameters such as rotational speed, travel speed and tilt angle were varied to obtain optimum weldment with no defect and high tensile strength, and then by adding zirconia nanoparticle to welding zone of optimum sample, the effects of pass number on microstructure, mechanical properties and wear characteristics of welded specimens were investigated. In order to investigate microstructure, optical and scanning electron microscope and atomic force microscope was used. Results showed that by increasing pass number, the distribution of nanoparticles in the matrix become more homogenous and grain size in the stir zone has considerably decreased. The reason of this phenomena could be attributed to the presence of reinforcement nanoparticles which it causes pinning the grain boundary, enhancing nucleation of new recrystallized grains and the effect on breaking of initial grains. The maximum microhardness and tensile strength of weldment were obtained for composite weldment after four pass of 111 Hv and 328.3 MPa, which these values were 24 and 26% higher than weldment without reinforcement. Wear resistance of the weldment was determined by pin on disk test and revealed that by increasing pass number of FSW, the wear resistance increased.

Friction stir processing (FSP) is a method for improvement surface. This process development for refinement of microstructure, improvement of materials mechanicals properties so production of surfsce composite. The aim of article product metal matrix composite (MMC) on surface of copper sheets by means of SiO2 refinement by friction stir processing for improve mechanical properties. In this article travel speed was fixed and56 mm/min and rotationals speed were 500, 710, 1000 rpm to sue. Optimum sample selected due to microstructure resualts and highest mechanical properties. Microstructure resualts reported by optical and scaning electron microscopical. Resualt indicating via increase rotational speed, increase size and decrase hardness. Maximum hardness related to specimen whit rotational speed 500 rpm, and 121 Hv, least size 10µm. so tensile properties statement white standard tensile test. Resualt of mechanichal surface composite were about on 218 to 227 Mpa respectively. At last wear properties of surface composite were investigated. The resualt of wear test exhibiting better wear behaviour of the developed composite.

The purpose of this investigation was the fabrication of surface nano composite composed of aluminum 2024 and boron carbide particles with the average size of 60 nm by the friction stir processing (FSP) method. The primary FSP tests showed that the rotating speed of 850 rpm and traverse speed of 25 mm/min are the optimum conditions which results in sound defect free samples. Then, the effect of nano particles addition and number of passes were analyzed in the fabricated samples. Optical and field emission scanning electron microscopy techniques showed that the average grain size in the stirring zone decreases by adding nanoparticles to the matrix and increasing the number of FSP passes. The hardness and the abrasion tests showed that strength and wear resistance of the fabricated samples increases with increase in number of passes. The improvement in the mechanical properties was attributed to the uniform distribution of the reinforcing particle and grain refinement. However, in the FSPed base metal the hardness was decreased due to the dissolution of primary strengthening particles during the FSP process. The result of electrochemical tests indicated that corrosion behavior of the FSPed samples improves by adding the reinforcing particles and increasing the pass number.

In this study, A356 aluminum alloy matrixcomposites reinforced with different weight percentages of SiC nano- and microparticles respectively with 50 nm and 5 µm average particle sizes were fabricated by stir casting method. Due to the effect of T6 heat treatment on the strength and hardness of A356alloy, the obtained composites were subjected to the T6 heat treatment. The mechanical properties such as hardness and compressive properties of the composites were investigated. Microstructures of the samples were also investigated by an optical microscope (OM), scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). Microstructural investigation indicated that T6 heat treatment led to thechange of eutectic silicon morphology and formation of theMg2Si precipitates during age hardening stage, leading to increase the hardness and compressive strength. The results showed that an increase in wt.% of nanoparticles led to an increase in hardness and compressive strength. The results of microstructural investigationshowedthe relatively uniform distribution of reinforcement particles. Also, the strength and hardness of the composites reinforced with nanoparticleswere greater than those of the composite reinforced with microparticles, even with higher weight percent of reinforcement particles. Hardness and compressive strength at 35% strain for the composite reinforced with 1.5 wt.% nanoparticles were respectively obtained 62 HBN and 252MPa, which are improved compared to the base alloy.

Hybrid ratio of each reinforcement phases in hybrid composite can be defined as proportion of its volume to total reinforcement volume of the composite. The hybrid ratio is an important factor which controls the participation extent of each reinforcement phases in overall properties of hybrid composites. Hence, in the present work, surface hybrid nano composites of Al2024, Graphite average particle size of 100 μm and ZrO2 average particle size of 15 with different. For fabrication of nano composite the tool rotation rate was set to be 1000 rpm, and its advancing speed was 20 mm/min and tilt angle of 3 degree were chosen and all samples were subjected to 2 passes of FSP to obtain more homogeneous dispersion of the reinforcements. Subsequently, effect of hybrid ratio on microstructural, mechanical and tribological properties investigated. Optical microscopy and scanning electron microscopy were utilized to perform microstructural observation on the samples showed that reinforcements are well dispersed inside the Nugget Zone. Hardness value measurements and pin on disk dry sliding wear tests were carried out to investigate effect of hybrid ratio on mechanical and tribological properties of the nano composites.

Friction stir processing (FSP) is a novel process for refinement of microstructure, improvement of material’s mechanical properties and production of surface layer composites. In this investigation via friction stir processing, metal matrix composite (MMC) was fabricated on surface of 5083 aluminum sheets by means of 5 μm SiC particles. First combination of rotational speed and travelling speeds were performed. Optimum condition was selected due to highest tensile strength. It was seen that sample which fabricated by 1000rpm and 28mm/min had improvement in tensile strength in comparison to other conditions. After that the effect of multipass on the optimum sample were investigated. The friction processed surface composite layer was analyzed through optical and scanning electron microscopical studies. Mechanical properties of the friction stir processed surface composites were evaluated through microhardness and universal tensile tests. The results were compared with the properties of the base metal. The surface composite layer resulted in that change of tool rotational direction between FSP four passes exhibited better properties in hardness, tensile behavior and wear resistance compared to the behavior of the base metal. The microhardness and tensile strength of the as-received alloy, and surface composite after that change of tool rotational direction between four passes specimens were about 85Hv and 285 MPa, 118Hv and 316 MPa, respectively.

The fabrication of nano‐composites is quite challenging because uniform dispersion of nano‐sized reinforcements in metallic substrate is difficult to achieve using powder metallurgy or liquid processing methods. Friction stir processing (FSP) is a new solid-state process used to modify the refinement of microstructure, improvement of material’s mechanical properties and production of surface layer composites. In this investigation via friction stir processing, metal matrix composite surface (MMCs) was fabricated on surface of 5083 aluminum sheets by means of 5 μm and 80 nm TiO2 particles. The friction processed surface composite layer was analyzed throughoptical and scanning electron microscopical studies. Effects of reinforcing particle size and FSP pass number on the microstructure, microhardness, on tensile and wear properties of the developed surfaces were investigated. Results show that the created nanocomposite layer by TiO2 particles exhibits a microstructure with smaller grains and higher hardness, strength, and elongation compared to the composite TiO2 layer by particles. Increasing FSP pass number results in improved distribution of particles, finer grains, and higher hardness, strength, elongation, and wear resistance. The surface composite layer resulted in four passes with change in rotation direction with nano particle reinforcement exhibited better properties in hardness, tensile behavior and wear resistance compared tothe behavior of the base metal.