Si Aluminum Alloy Research Articles

Effects of Fe, Mn Contents on the Al Alloys and STD61 Steel Die Soldering

Recently, various attempts to produce a heat sink made of Al 6xxx alloys have been carried out using die-casting. In order to apply die-casting, the Al alloys should be verified for die-soldering ability with die steel. It is generally well known that both Fe and Mn contents have effects on decreasing die soldering, especially with aluminum alloys containing substantial amounts of Si. However, die soldering has not been widely studied for the low Si aluminum (1.0~2.0wt%) alloys. Therefore, in this study, an investigation was performed to consider how the soldering phenomena were affected by Fe and Mn contents in low Si aluminum alloys. Each aluminum alloy was melted and held at <TEX>$680^{\circ}C$</TEX>. Then, STD61 substrate was dipped for 2 hr in the melt. The specimens, which were air cooled, were observed using a scanning electron microscope and were line analyzed by an electron probe micro analyzer. The SEM results of the dipping soldering test showed an Al-Fe inter-metallic layer in the microstructure. With increasing Fe content up to 0.35%, the Al-Fe inter-metallic layer became thicker. In Al-1.0%Si alloy, the additional content of Mn also increased the thickness of the inter-metallic layer compared to that in the alloy without Mn. In addition, EPMA analysis showed that Al-Fe inter-metallic compounds such as <TEX>$Al_2Fe$</TEX>, <TEX>$Al_3Fe$</TEX>, and <TEX>$Al_5Fe_2$</TEX> formed in the die soldering layers.

Optimisation and sensitivity analysis of friction stir spot-welding process parameters for joining AA 6061 aluminum alloy

Al- Mg- Si aluminum alloy has gathered wide acceptance in automotive industries requiring a high strength-to weight ratio and good corrosion resistance. The friction stir spot welding process is a variant of linear friction stir welding process in which the material is being welded without bulk melting. The FSSW parameters such as tool rotational speed, plunge rate, plunge depth, dwell time play major role in determining the strength of the joints. A central composite rotatable design with four factors and five levels has been chosen. An empirical relationship is established to predict the tensile shear fracture load of friction stir spot-welded AA6061 aluminum alloy by incorporating independently controllable FSSW process parameters. Response Surface Methodology is applied to optimise the FSSW parameters to attain maximum lap shear strength of the spot weld and sensitivity analysis is carried out to study the impact of process parameters on output.

The GA Optimization Performance in the Microstructure and Mechanical Properties of MMNCs

This paper is aimed at development of an effective approach based on the combination of GA, FEM and artificial intelligent methods to determine the optimum conditions of Al Matrix nano composites in terms of microstructure and mechanical properties. Using the stir casting method, alumina nano-particles were incorporated into the Al–Si aluminum alloy. Characterization of the mechanical properties showed that the presence of nano particles significantly improved the hardness and strength of the composites. Then artificial neural network and finite element technique were implemented in order to predict the mechanical properties and genetic algorithms were used for the process conditions optimization. It was revealed that the proposed model is a useful and efficient method to find the optimal process conditions in stir casting.

Effect of Zr addition on properties of Al–Mg–Si aluminum alloy used for all aluminum alloy conductor

The effects of Zr addition on mechanical property in the aged Al–Mg–Si alloy exposed to thermal-resistant treatment (180–250 °C) have been studied by using both Brinell Hardness tests and tensile tests. The softening process at 180 °C and 230 °C has been investigated by transmission electron microscope (TEM). The Arrhenius Model is introduced to simulate the strength evolution in the thermal-resistant treatment. The results show that tensile strength and thermal-resistant property are improved by addition of Zr, and both the Brinell Hardness and Tensile Strength could maintain no less than 90% of their initial values when the alloy is exposed to heat treatment at 180 °C for 400 h and 230 °C for 2 h. The presence of rod-shaped phases and coarsening particles results in decreasing the hardness of the sample. The relationship between thermal-resistant life and temperature is derived by the Arrhenius Model. When the Al–Mg–Si–Zr alloy is heated at 130 °C, the duration described in the Arrhenius plot could reach to 40 years.

Microstructure and properties of rheo-diecast Al-20Si-2Cu-1Ni-0.4Mg alloy with direct ultrasonic vibration process

The microstructure and properties of Al-20Si-2Cu-1Ni-0.4Mg alloy fabricated with semi-solid rheo-diecasting process were studied. A newly developed direct ultrasonic vibration process (DUV process) was used in the preparation of the semi-solid slurry of this alloy. The results show that the primary Si particles in this alloy is about 20 μm in size under DUV for 90 s in the semi-solid temperature range, compared to about 30 μm in the alloy without DUV. It is discovered that the primary Si particles distribute more homogeneously and have regular shape, but have lower volume fraction after DUV. The tensile strength at room temperature is about 310 MPa, and the tensile strength and elongation of the semi-solid die castings are increased by 34% and 45%, respectively, compared with the traditional liquid die castings. The high-temperature tensile strength at 300 °C of this high Si aluminum alloy reaches 167 MPa, and the coefficient of thermal expansion is 17.37×10 −6/°C between 25 and 300 °C. This indicates that this high Si content Al-Si alloy produced with the DUV process is suitable to be used in the manufacture of pistons or other heat-resistant parts.

Corrosion Behavior of Protective Coating Film Fabricated by PEO Process in High Si Aluminum Alloy

not Available.

Effect of post-heat treatment on the fatigue behaviour of a friction stir spot-welded Al–Mg–Si alloy

In this paper, the effect of post heat treatment on fatigue behaviour of friction stir spot welded Al–Mg–Si aluminium alloy was investigated. The microstructure of the weld zone was classified into two regions: stir zone (SZ) and mixed zone (MZ), where fine equiaxed grains due to dynamic recrystallization were observed. Two kinds of post heat treatment, namely aging and T6 treatment, were applied to the as-welded joints. The grains in the SZ and MZ were extremely enlarged only by T6 treatment, but some fine grains still remained near the boundary of MZ. Fatigue tests were conducted using lap-shear specimens at a stress ratio R = 0.1. Post heat treatments exhibited little influence on fatigue strength, but fatigue fracture morphology was dependent on both load level and post heat treatment. At high applied loads, fatigue fracture took place through the MZ in the as-welded and aged joints, while along the boundary of MZ in the T6 treated joint. At low applied loads, the fatigue crack initiated at the edge of the nugget and then propagated through the upper sheet in the as-welded joint, but the lower sheet in the aged and T6 treated joints. The dependence of fracture morphology on post heat treatment was attributed to the change of microstructures and hardness distribution around the nugget by post heat treatment.

Microstructure and texture assessment of Al–Mn–Fe–Si (3003) aluminum alloy produced by continuous and semicontinuous casting processes

Aluminum sheets are currently produced by the direct-chill process (DC). The need for low-cost aluminum sheets is a challenge for the development of new materials produced by the twin roll caster (TRC) process. It is expected that sheets produced from these different casting procedures will differ in their microstructure. These differences in microstructure and in the crystallographic texture have great impact on sheet mechanical properties and formability. The present study investigated microstructure and evaluated texture of two strips of Al–Mn-Fe–Si (3003) aluminum alloy produced by TRC and by hot-rolling processes. It was possible to notice that the microstructure, morphology, and grain size of the TRC sample were more homogenous than those found in hot-rolled samples. Both strips, obtained by the two processes, showed strong texture gradient across the thickness.

The influence of dispersoids on the recrystallization of aluminium alloys

Abstract The influence of dispersoids on the softening processes in twin-roll cast and cold-rolled Al – Fe – Mn – Si aluminium alloy was studied. Before rolling, the specimens were thermo-mechanically pre-treated in order to create a different second-phase dispersion. The influence of the initial microstructure was studied by means of electrical resistivity, light and electron microscopy. The evolution of softening was monitored by microhardness measurements. The depletion of the Al matrix from solutes connected with formation of a dense dispersion of precipitates results in the enhancement of (sub)grain-boundary mobility. As a consequence, full recrystallization occurs at lower temperatures in pre-annealed specimens with low solute concentrations. The presence of coarser precipitates formed during the pre-treatment results in the formation of a fine-grained microstructure.

Dissimilar aluminium weldability of SiC particle reinforced aluminium alloy to Al–Si, Al–Mg, Al–Mg–Si, Al–Zn–Mg–Cu alloys by electron beam welding

The SiC particle reinforced aluminum alloy has been developed for various machine parts. Aluminum welded machine parts often require welded joints composed of dissimilar alloys. In the present study, electron beam weldability of dissimilar joints was investigated on different combinations of aluminum alloys of 10 mm thickness. The main alloy is 10% SiC particle reinforced Al–Si aluminum alloy. Combination wrought alloys are Al–Si, Al–Mg, Al–Mg–Si and Al–Zn–Mg–Cu alloys. The electron beam machine is a 6 kW high voltage type. The joint groove is of square butt without filler metal. In the case of SiC reinforced alloy/Al–Si and Al–Mg, joints, weldability was poor because some weld imperfections were recognized such as arcing and other defects. In the case of SiC reinforced alloy/Al–Mg–Si, Al–Zn–Mg–Cu, the cracking sensitivity is low while some small porosity was recognized. Tensile strength became about 150 MPa such as SiC reinforced alloy. Impact values of the SiC reinforced alloy/Al–Mg–Si joint were recovered through 2160 h room temperature ageing. Micro segregation of the Si element was recognized for the SiC reinforced alloy/Al–Mg–Si joint by electron probe microanalyser analysis.

S1302-1-1 高Siアルミニウム合金の超精密切削に関する研究(超精密加工(1))

The objective of this study is to clarify a mechanism of the surface formation in ultraprecision cutting of high Si aluminum alloys using a single point diamond tool. For this purpose, ultraprecision cutting experiments of AC9A aluminum alloy have been conducted by means of the fly-cutting method using a single crystal diamond tool with a round nose. When the feed rate is smaller than a critical feed rate under a constant cutting speed and a constant depth of cut, the ductile mode cutting can be performed on Si particles.

Structure and properties of 6061 + 26 mass% Si aluminum alloy produced via coupled rapid solidification and KOBO-extrusion of powder

Experiments on mechanical consolidation of rapidly solidified (RS) powder of 6061 + 26 mass% Si alloy were performed using the oscillating-die extrusion method. The RS powder was wrapped in thin-wall 6061-alloy cup 35 mm in diameter and vacuum-compressed by means of 100 ton press. Bars 8 mm in diameter were extruded with cross-section reduction of λ = 19 without any preheating of the charge. Tubes with a diameter/wall thickness of 14 mm/1 mm and cross-section reduction of λ = 33 were also manufactured with success. TEM/STEM observations revealed a very fine structure of as-extruded material and bimodal distribution of quasi-spherical silicon particles. Statistical analysis revealed a silicon fine fraction of 0.1–0.7 μm and a coarse fraction 2.1–2.5 μm in diameter. Examination by means of TEM did not reveal any significant changes in the morphology of the silicon particles, even when a high extrusion ratio and the material annealing after deformation were used. Hot compression tests on as-extruded rods ( λ = 19) and preliminary annealed samples were performed at a constant true strain rate of 5 × 10 −3 s −1 within the temperature range of 293–823 K. High strength of the material and relatively high ductility of samples deformed by compression up to ɛ t ≅ 0.4 were observed. The maximum flow stress value for as-extruded material was reduced with deformation temperature from ∼390 to ∼3.5 MPa for 293 and 823 K, respectively. Annealing of the samples at 773 K/30 min was found to reduce the maximum flow stress by 30–40%. Tensile strengths of similar as-cast alloys and materials manufactured by means of other powder metallurgy methods were shown for the purpose of comparison.

Effect of re-filling probe hole on tensile failure and fatigue behaviour of friction stir spot welded joints in Al–Mg–Si alloy

In this study, the fatigue behaviour of Al–Mg–Si aluminium alloy joints joined by friction stir spot welding (FSSW) was investigated. FSSW was performed using a specially designed double-acting tool consisting of outer flat shoulder and inner retractable probe, which could re-fill probe hole of the joints. Lap-shear specimens with probe hole and re-filled one were fabricated. The tensile strength of the joint with re-filled hole was higher than that of the joint with probe hole, where shear fracture through the nugget occurred in both joints. The re-filling process increased effective cross sectional area of the nugget, resulting in higher tensile strength. Fatigue tests were conducted using lap-shear specimens at a stress ratio of R = 0.1. The fatigue strength of the joint with re-filled probe hole was nearly the same as, but lower than, at low and high applied loads, respectively, that of the joint with probe hole. The pull out of the nugget, i.e., plug type fracture, was seen in the joint with re-filled probe hole, while shear fracture through the nugget was observed in the joint with prove hole. The observation of fatigue crack growth path revealed that the plug type fracture through the upper sheet was responsible for the observed lower fatigue strength of the joint with re-filled prove hole at high applied loads.

The surface characteristics of Al–7%Si aluminum alloy manufactured by thixo/rheoforming process through nanoindentation/atomic force microscopy

This study investigated nano/microsturcture and mechanical/tribological properties in the thixo/rheoformed A356 alloy parts using nano/microindentation and nanoscratch, incorporated with optical microscopy and atomic force microscopy (AFM). As a result, thixo-cast sample exhibited higher mechanical properties than rheo-cast, irrespective of grain size. The reason that mechanical properties of thixo-cast part was higher than that of rheo-cast, was interpreted by the effect of the eutectic region surrounded by the primary α phase on the hardness. It was also observed that shape and distribution of Si particles in the adjacent eutectic region to the primary α-Al phase of the thixo/rheo-cast products were different. By scratching surface of thixo/rheo-cast parts using a nanoindentor, friction forces and coefficients for the primary α-Al and eutectic phases in thixo-cast products were resulted to be higher than those in the rheo-cast. Nanoscratch for the thixo-cast product also revealed a rough and irregular surface compared to that for the rheo-cast, providing the evidence for the effect of eutectic entrapped by primary α-Al phase on mechanical properties.

Tensile Properties of Large Extrusion and Forgings of RS P/M Al-9Fe-1.9Mo-1.7Si Aluminum Alloy

Large extrusion and forgings of Al-9Fe-1.9Mo-1.7Si (wt.%, FMS0918) aluminum alloy for elevated temperature applications were produced by rapidly solidified powder metallurgy process. Powders of FMS0918 alloy were produced by inert gas atomization, and then screened, canned, degassed, extruded and forged. The extrusion exhibited good strengths and elongation in longitudinal orientation, but low elongation in long- and short-transverse orientations. After forged, the tensile strengths of the forgings showed little change, but the long- and short-transverse elongation was improved.

Dynamic precipitation during severe plastic deformation of an Al–Mg–Si aluminium alloy

The precipitation behavior during equal-channel angular pressing (ECAP) performed at room temperature and 175 °C in an Al–Mg–Si alloy has been investigated. Dynamic precipitation was in fact observed during severe plastic deformation at both temperatures and reasons for dynamic precipitation were analyzed and compared with that in conventional static aging. The interaction between precipitates and dislocations was investigated and strengthening mechanisms were discussed.

Experimental investigation for rheology forming process of Al–7% Si aluminum alloy with electromagnetic system

In this paper, an electromagnetic stirring system (EMS) was adapted to the forming process for manufacturing knuckles. After producing knuckles with EMS, the microstructures of the parts were investigated by image analysis and mechanical properties and then compared to parts fabricated by without using EMS. According to this comparison, the parts formed using EMS have better mechanical properties by over 30% and have globular microstructures.

Friction spot joining of an extruded Al–Mg–Si alloy

Friction spot joining was used to make lap joints on strips of an extruded Al–Mg–Si aluminium alloy. The influence of tool rotational speed, plunge rate and depth, and dwell time prior to tool retraction on the weld axial plunge force was monitored using high speed data acquisition. The effect of these parameters on bond formation and tensile shear strength of the resulting joints was determined. An optimum combination of parameters that maximises joint tensile shear strength was identified.

Influence of severe plastic deformation on aging of Al–Mg–Si alloys

The influence of severe plastic deformation induced by equal-channel angular pressing (ECAP) on the microstructure and aging was studied in two modified Al–Mg–Si aluminum alloys. The microstructure of both alloys after different heat treatments and deformation paths was characterized by X-ray diffraction and polarized-light microscopy. The effect of artificial aging was investigated on samples in the as-extruded condition after ECAP. The aging was monitored by hardness and electrical conductivity measurements. At higher aging temperature (170 °C), the alloys showed an increasing softening with time due to recovery or/and grain coarsening. At lower aging temperatures, the hardness remains almost constant owing to enhanced precipitation hardening.

Pre-aging to improve bake hardening in a twin-roll cast Al–Mg–Si alloy

Abstract Heat-treatable Al–Mg–Si aluminum alloys are increasingly used for automotive body panel applications. They are shipped and formed in T4 temper while still formable and are subsequently given a bake cycle to increase strength by age hardening while the paint is cured. The industrial paint-bake treatment, however, is too short to fully exploit the age hardening potential of these alloys. Hence, the microstructure in the conventional T4 temper must be modified by creating clusters that grow and readily transform into coherent precipitates upon paint baking. The present work was undertaken to improve the paint-bake response of a twin-roll cast 6016 sheet by employing artificial aging between the solution treatment and the paint-bake cycle. Pre-aging in a wide temperature range (60–200 °C) was effective in improving the bake hardening response of the twin-roll cast 6016 sheet which, when processed without any pre-aging, failed to meet in-service strength requirements with a rather poor bake hardening response of 35 MPa.