Purpose: CASTABILITY of Ni-Cr alloy as an-alternative to gold has an important role in the success of metal – ceramic restorations. This research evaluates the importance of adding Berilium (Be) to Ni - Cr alloy to compare the CASTABILITY of two Ni - Cr and Ni - Cr - Be alloys in reproducing different lengths of bevel finish line.Methods & Materials: Using Replica method, 30 wax-up with three different lengths of bevel were casted with Rexillium III and Wiron 99. After completing the necessary procedures, the bevel lengths were evaluated, and compared by t - test.Results: There was no significant difference between the CASTABILITY of these two alloys. The best castabilty in both alloys was seen in the range of 0.5 mm.Conclusion: It seems that Be is not necessary for a good CASTABILITY. Although an increase in volume/surface of wax-ups in a significant range can improve the CASTABILITY, the farther the margin of restoration located to the sprue, the more the possibility of incomplete castings. It seems the best castablity occurs in bevels of 0.5 mm.

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 tear 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.

Introduction: The aim of this study was to evaluate the effect of bridge orientation in casting machine on CASTABILITY and quality of base metal castings.Methods: Three groups of patterns with different direction and lengths in casting machine were casted and then studied qualitatively and quantitatively using mean and standard deviation in table of frequency.Results: Larger nodules and porosities were on the joints of sprue in horizontal specimens (P=0.01 and 0.048, respectively). There was no significant difference in CASTABILITY between 3-, 5-and 6-unit bridges in relation to their direction in casting machine (P=0.5). An increase in bridge length led to more variation in length and width. The position of bridges also played an important role in the length variation in bridges.Conclusion: The direction of bridges had no effect on base metal CASTABILITY but a vertical position resulted in a better casting quality and an increase in length of the bridges caused more defects in castings.

Statement of the Problem: The CASTABILITY of nonprecious gold color alloy using torch/ centrifugal and induction/vacuum-pressure casting techniques has not been studied yet. Purpose: This study was conducted to compare the CASTABILITY of nickel chromium, cobalt-chromium and nonprecious gold color alloy using torch/centrifugal and induction/ vacuum-pressure casting techniques. Materials and Method: In this in vitro study, a total number of 54 identical acrylic wax meshes were prepared and divided into 6 different groups of 9 each. Group 1: nickel-chromium alloy, which was casted with induction technique. Group 2: nickel-chromium alloy was casted with centrifugal technique. Group 3: cobalt-chromium alloy was casted with induction technique. Group 4: cobalt-chromium alloy was casted with centrifugal technique. Group 5: nonprecious gold color alloy was casted with induction technique. Group 6: nonprecious gold color alloy was casted with centrifugal technique. Then castabil-ity of specimens was measured using modified Whitlock’ s method. The results were ana-lyzed using two way ANOVA and post hoc tests. Results: ANOVA test revealed no statistically significant difference between different alloys with a p Value of 0. 313. Moreover, it represented no significant differences within the groups regarding alloy types and casting techniques with a p Value of 0. 511 and 0. 682, respectively. Conclusion: No significant difference was found in the CASTABILITY value of nickel-chromium, cobalt-chromium, and nonprecious gold color alloys. In addition, the CASTABILITY value of three alloys tested in this study was not different by using torch/centrifugal or in-duction/vacuum-pressure casting machines.

Magnesium alloys are very attractive materials owing to their properties of low density, high specific strength and stiffness, good CASTABILITY, and weldability. AZ31 magnesium alloys show better situation in terms of weldability than the other, so it has more applications than other magnesium alloys. In this study, TIG and pulsed TIG welding method was used to welding the AZ31 alloy and finally microstructure and mechanical properties of welds with metallography, scanning electron microscopy, tensile test were examined. The results showed that the heat input affected the size of grains that are leading to changes in mechanical properties. Sample was welded with TIG welding with minimum current has maximum strength among the samples both pulsed TIG welding and TIG method. It is observed that with increasing frequency in TIG welding, strength is reduced. Despite the same IP and IB, higher frequency has created a stronger welding. Also increases the frequency leads to more fine-grained samples, resulting in increased strength.

LM13 alloy is widely used in piston industry due to its low coefficient of thermal expansion, excellent CASTABILITY and hot tear resistance. In this research, effect of casting process on wear behavior of LM 13 alloy was investigated. First, samples were produced using two casting processes and heat treatment. Then wear behavior of these samples under dry sliding condition was examined. Results of hardness and strength tests indicated that squeeze cast specimens exhibited higher mechanical properties. Wear experimental results showed that in both squeeze and gravity cast specimens, the amount of weight loss increases with increase in sliding distance which is accompanied by reduction in wear rate and friction coefficient. A comparison between two samples demonstrated that squeeze sample had better tribological behavior. Casting process variation causes decrease in friction coefficient from 0.4 to 0.2 for squeeze cast samples and decrease in weight loss of these samples. Squeeze cast samples had better surface quality and in these samples abrasive, adhesive and delamination are dominant wear mechanisms, while in gravity cast samples abrasive, adhesive and surface fatigue are the dominant wear mechanisms.

Aluminum-Silicon alloys have a wide application in different industries. AS5U3G aluminum alloy is a hypoeutectic Al-Si alloy, in which silicon and copper are the main alloying elements. Silicon increases CASTABILITY and resistance to hot tearing of the alloy. Copper increases high-temperature tensile strength and improves the machinability of the alloy. Therefore, this alloy has been widely used in the manufacturing of automobile engine parts. Modification treatment by strontium has a major influence on the properties of the alloy. In this research, electrical conductivity has been used to evaluate the modification and dendrite arm spacing (DAS) of the alloy as a non-destructive testing. Different levels of strontium have been added to the melt and electrical conductivity of the samples measured after solidification.The results indicate that electrical conductivity increases with modification improvement and its maximum value is obtained at full-modified state. Therefore, the modification rate of the alloys may be estimated before melt pouring and casting by measuring electrical conductivity. Non-destructive evaluating of DAS has also been done in both modified and un-modified samples.

hypereutectic Al-Si alloy piston has great potential for use in the automotive industry, especially for engine components, due to its lightweight, excellent CASTABILITY, good thermal conductivity, high strength and excellent corrosion resistance. The silicon content in the A390 is between 17-18%. This article presents various shapes of dimples that can be fabricated on a cylindrical shape part of A390 using the turning process with aid of dynamic assisted tooling (DATT). To minimize the number of the experiment, the Taguchi method, with an L8 orthogonal array, was used to accommodate two different sets of seven parameters used in the fabrication of dimpled structures, i. e. cutting speed of 2-9 m/min, feed rate of 0. 4-0. 6 mm/rev, DOC of 0. 05-0. 01 mm, frequency of 15-28 Hertz, the amplitude of 1-3 mm, using two different cutting tool i) rake angle of +4o and-8. 5o, relief angle of 4o and 7o, and nose radius of 0. 4 and 0. 8 mm, ii) Rake angle of +9°,and-20°, , and relief angle of +7°,and +17°, , and nose radius 8 mm. By using these turning parameters, 3 dimple shapes were produced,spherical, short drop and long drop shapes, with almost square and hexagonal arrays.

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 0C/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.