Squeeze-cast Alloy Research Articles

Microstructure and Tensile Properties of Squeeze Cast Magnesium Alloy AM50

High-pressure die cast magnesium alloy AM50 is currently used extensively in large and complex shaped thin-wall automotive components. For further expansion of the alloy usage in automobiles, novelmanufacturing processes need to be developed. In this study, squeeze casting of AM50 alloy with a relatively thick cross section was carried out using a hydraulic press with an applied pressure of 70 MPa. Microstructure and mechanical properties of the squeeze cast AM50 with a cross-section thickness of 10 mm were characterized in comparison with the die cast counterpart. The squeeze cast AM50 alloy exhibits virtually no porosity in the microstructure as evaluated by both optical microscopy and the density measurement technique. The results of tensile testing indicate the improved tensile properties, specifically ultimate tensile strength and elongation, for the squeeze cast samples over the conventional high-pressure die cast parts. The analysis of tensile behavior show that the strain-hardening rate during the plastic deformation of the squeeze cast specimens is constantly higher than that of the die cast specimens. The scanning electron microscopy fractography evidently reveals the ductile fracture features of the squeeze cast alloy AM50.

Comparison of Corrosion Properties of Squeeze Cast and Thixocast MgZnRE Alloys

Thixocasting is a new semi-solid processing route for magnesium alloys; it is claimed that finer microstructures can be produced and as a consequence, better corrosion resistance can be achieved. Therefore, it is of great interest to compare the corrosion properties of two Mg-Zn-RE alloys produced by standard squeeze casting and new semi-solid casting technique. The influence of the two different processing routes and the replacement of rare earth elements by Ca additions on the corrosion behavior were studied in NaCl aqueous solutions by (a) analyzing the corrosion morphology, (b) measuring electrochemical polarization curves, and (c) carrying immersion tests at constant pH-value. Using light microscopy, scanning electron microscopy and X-ray diffraction, the corrosion results were related to the microstructures on the specific alloys. The results indicate that Ca cannot replace rare earth elements under corrosion aspects, but they also showed that the thixocasting process resulted in better corrosion resistance.

Microstructure characterization and tensile properties of squeeze-cast AlSiMg alloys

A research program was conducted to study the effects of squeeze pressure (70, 100 and 160 MPa) and heat treatment T6 on the structure, hardness and tensile properties of cast Al6Si0.3Mg alloys. The influence of squeeze pressure on macro- and microstructures of Al6Si0.3Mg alloys has been investigated. Some of castings were solution treated at 540 °C for various times and others were subjected to aging at 170 °C after solution treatment. The results indicated that precipitation occurred within about 30 min for both cast and squeeze cast alloys. The hardness began to increase and maximum values were observed after about 10 h for as-cast alloy. Increasing of squeeze pressure (70–160 MPa) accelerated strength of the alloys from 8 to 4 h, respectively. Squeeze pressures decreased the percentage of porosity and increased the density, also it decreased the grain size of α-Al and modified the Si eutectic. Hardness and tensile properties increased with both heat treatment and increasing of squeeze pressure.

Hot tensile and fatigue behaviour of zinc–aluminum alloys produced by gravity and squeeze casting

The tensile and fatigue properties of zinc–aluminum alloys (ZA-8, ZA-12 and ZA-27) in squeeze and gravity cast forms have been investigated. Tensile tests were conducted at ambient and elevated temperatures up to 150 °C. At low temperatures, the ultimate tensile strength and yielding strength of the squeeze cast alloys have been found to be superior those of the gravity-cast alloys, as the temperature increased they decreased. In the same way, Brinell hardness of the squeeze cast alloys were obtained at higher values than gravity castings. The fatigue tests were performed at a constant speed of 400 rev/min and under a number of stress levels ranging from 100 to 150 MPa. The fatigue behaviour results of the ZA alloys were similar to obtained from the tensile testing. The squeeze cast alloys exhibited good fatigue resistance in proportion to the gravity castings. Metallography examinations showed that the microstructure of the castings differed according to the method of casting used. It was considered that the mechanical properties of the alloys were affected from these micro-structural changes.

Process optimisation for a squeeze cast magnesium alloy

The paper reports the influence of key process variables on zirconium-free (RZ5DF) and zirconium-containing (RZ5) magnesium–zinc–rare earths alloys by examination of the microstructure and mechanical properties of specimens produced by squeeze casting. Applied pressures from 0.1 to 120 MPa were considered and it was established that an applied pressure greater than 40 MPa was required to suppress the formation of microporosity. Increasing the applied pressure from 0.1 to 60 MPa, produced a reduction in cell size from 127 to 21 μm. The metal pouring and die temperatures considered in the investigation were within the range of 720–780 and 225–275 °C, respectively. It was established that the intermediate die temperature of 250 °C produced the highest tensile properties and that the presence of zirconium did not improve the as-cast properties of the squeeze cast alloy. The highest UTS value obtained for the zirconium-free RZ5DF alloy was 198 MPa compared to 195 MPa for the ZR5 alloy. These UTS value were approximately 50% higher than those for material cast under atmospheric pressure.

Phase transformations due to isochronal annealing of Mg – rare earth – Sc–Mn squeeze cast alloys

Abstract Magnesium alloys containing rare earths (Gd, Y, Ce, ≈ 3–10 wt.%), Sc (< 1 wt.%) and Mn (≈ 1 wt.%) were squeeze cast. Electrical resistivity and hardness responses to isochronal annealing were measured in the range 20–580°C and phase changes responsible were identified by transmission electron microscopy. In alloys containing Gd and Y simultaneous precipitation of three phases takes place, namely the metastable c-base-centred orthorhombic phase (Mg–Y, Mg–Gd) in the form of prismatic plates, the thermally stable hexagonal Mn2Sc phase in the form of fine basal discs and a metastable hexagonal coherent phase, containing Mn and Y or Gd, in the form of very thin basal plates (missing in the Mg alloy with 10 wt.% Gd). In the Ce-containing alloy the Mg12Ce tetragonal phase, present after casting in various forms, transforms into a rod-like form. Simultaneously, fine Mn2Sc discs precipitate on basal planes and the grain boundary eutectic transforms to the equilibrium phases.

Mechanical properties and creep of Mg – rare earth – Sc – Mn squeeze cast alloys

AbstractThe microstructure developed during the T5 treatment of squeeze cast magnesium alloys containing rare earth (Gd, Y, or Ce, ≈ 3–10 wt.%), Sc (&lt; 1 wt.%) and Mn (&lt; 1.5 wt.%) is responsible for a reasonable age hardening in MgGdScMn alloys. Moderate age hardening is only possible in MgY4Sc1Mn1 or MgCe3Sc1Mn1 alloys. The c‐based centred orthorhombic phase precipitating as fine prismatic plates in a triangular arrangement is the most effective hardening phase. The stability of yield strength up to 250°C–300°C was confirmed in T5 treated MgGdScMn and MgY4Sc1Mn1 alloys. All alloys exhibit a reasonable ductility at room temperature. The precipitation of very fine basal discs of Mn2Sc phase observed in all T5 treated alloys investigated does not contribute considerably to the hardness, but it is very effective in restricting creep. The creep resistance of all alloys investigated is superior to that of commercial WE54 alloy up to 350°C.

On the Growth of Small Fatigue Cracks in Two Squeeze-Cast Aluminum Alloys

It is now recognized that the fatigue lifetime of many structural components is determined by the rate of growth of small fatigue cracks. However it is not a straightforward matter to analyze the growth of these small cracks through the use of a traditional linear-elastic fracture mechanics approach for the following reasons: (1) on going from the micro-crack growth range to the macro-crack growth range, fatigue crack growth behavior undergoes a transition from stress control to stress intensity factor control; (2) because of the large plastic zone size to crack length ratio in the small crack growth regime, crack growth is elastic-plastic in nature rather than linear-elastic, and (3) the crack closure level increases from zero up to the level associated with a macroscopic fatigue crack as the fatigue crack increases in length in the small crack regime. The present paper presents an analysis of short crack growth data in two squeeze-cast aluminum alloys, and also discusses the Nisitani-Goto elastic-plastic relationship for fatigue crack growth.

Tensile Behavior of Mg&amp;ndash;Zn&amp;ndash;Ca&amp;ndash;Zr Alloy Forged in Semi-Solid State

The Mg-6.0%Zn-2.0%Ca-1.5%Zr (mass%) alloy is suitable for a prematerial alloy in semi-solid forging because of its fine spherical structure and ignition-proof property. The tensile behavior dependent on the microstructural factors, such as size and form factor of primary α phase and the distance of crack propagation in the semi-solid forged alloys with solid fractions of 65 and 70% is clarified. The tensile properties are compared to those of the squeeze cast alloy as well. The size of primary α phase increases with an increase in holding time. In contrast, the size of remelted and resolidified α phase remains unchanged. The tensile strength and 0.2% proof stress of the semi-solid forged alloys decrease as the size of the ripened primary α phase increases, indicating the dependence of strength on the size of the ripened primary α phase. The elongation increases with an increase in holding time. The result is interpreted by the facts that the distance of crack propagation increases due to the increasing size of the ripened primary α phase and that the form factor of the ripened primary α phase is lowered by tensile deformation with an increasing holding time. The remelted and resolidified α phase has no effect on the tensile properties with an increase in holding time. The elongation of semi-solid forged alloy is approximately two times larger than that of the squeeze cast alloy.

アルミニウム鋳造の最新技術 結晶微細化した亜共晶Ａｌ‐Ｓｉ‐Ｃｕ合金の半溶融加圧鋳造組織と機械的性質

Change in the morphology of dendrite primary crystals heated at a temperature of solidification range was examined in hypoeutectic Al–Si–Cu alloys. Dendritic α–Al crystals, which have been refined by the addition of grain refiner, Ti–B and cast into copper mold with the cooling rate more than 10 K/s, are easily spheroidized only by heating to semi-solid state. The size of spheroidized α–Al phases is about 100 μm in diameter under the semi-solid state of fraction solid 0.4 at 860 K. This morphology of α–Al crystals is suitable for the semi-solid squeeze casting. Semi-solid squeeze cast Al–7% Si–3%Cu alloys containing 0.1~1.0%Fe have superior in tensile properties, especially in elongation. The elongation of an as-cast alloy containing 1%Fe is 9%. The tensile properties of semi-solid squeeze cast alloys are further improved by solution heat treatment.

Effects of pressure, die, and stress-relief temperatures on the residual stresses and mechanical properties of squeeze-cast aluminum rods

The effects of die heating and stress-relief temperatures in reducing residual stresses of squeeze-cast aluminum alloy rods are experimentally determined by the longitudinal slitting method, and their reduction effects on the mechanical properties of the squeeze-cast alloy rods are investigated. Stress relief is much more effective than die heating in reducing residual stresses of the squeeze-cast alloy. Stress relief is substantially completed at 350 ° in 1 h, but at the expense of reduction in strength and hardness. Appreciable reduction in strength and hardness is avoided by using a stress-relief temperature of 250 ° for residual stress reduction of squeeze-cast aluminum alloy. Die heating to a maximum of 200 ° is considered adequate to substantially reduce the chilling effect of the metal mold on the solidifying molten metal and to avoid appreciable reduction of strength and hardness resulting from die heating effects.

Eutectic channelling in a squeeze cast Al-4.5Wt%Cu alloy

The purpose of this study was to investigate to what extent macrosegregation occurs during the squeeze casting of a simple cylindrical shape in an Al-4.5wt%Cu alloy. The application of 100 MPa pressure during solidification caused a sharp increase in the cooling rate, to an average value of about 14 Ks{sup {minus}1}. At this cooling rate the liquidus temperature was resolvable, however it was difficult to observe the eutective thermal arrest. The macrostructure was characterized by a V-shaped pattern that extended over a large fraction of the ingot cross-section. The V-shaped segregates were regions which consisted of a mixture of the {alpha}-Al phase, the {alpha}-Al + {theta}-Al{sub 2}Cu eutectic and pro-eutectic {theta}-Al{sub 2}Cu particles. The exact cause of the formation of the eutectic channels in squeeze cast alloys is unclear. A previous explanation was that the V-shaped channels in squeeze castings are produced along the liquid metal feeding path. However, as the segregated channels are very large, these regions should be relatively easily fed during solidification. Also, as the solidification process occurs under near hydrostatic pressure, it is unclear where the driving force for the filling of these channels could come from. A simpler explanation may be that the macrosegregation ismore » an effect of the different thermal conditions during solidification that exist between gravity and squeeze casting.« less

Influence of Microstructures on the Crack Growth Behavior of Small Fatigue Cracks in Squeeze-Cast Aluminium Alloys.

Influence of Microstructures on the Crack Growth Behavior of Small Fatigue Cracks in Squeeze-Cast Aluminium Alloys.

Newly developed Fe-Si-Al alloy heads by squeeze casting

Audio heads made of Fe-Si-Al alloy head cores by a squeeze casting were newly developed. The heads had merits of a low noise and a small distortion. A head wear of the squeeze cast alloy heads was reduced to 1/5 of that of conventional Fe-Si-Al alloy heads and was noted to be comparable to that of ferrite heads. Squeeze cast alloys (SCA) had magnetic properties of : <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\mu \geq 10,000</tex> at 1 KHz (thickness of 150 μm) before and after molding cores in a resin, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H_{c}\leq0.03</tex> Oe and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B_{10}\geq 8000</tex> G.