Effects of Solidification Cooling Rate on the Microstructure and Mechanical Properties of a Cast Al-Si-Cu-Mg-Ni Piston Alloy

Abstract

The effects of cooling rate 0.15, 1.5, 15, 150, and 1.5 × 105 °C/s on the microstructures and mechanical properties of Al-13Si-4Cu-1Mg-2Ni cast piston alloy were investigated. The results show that with an increase of solidification cooling rate, the secondary dendrite arm spacing (SDAS) of this model alloy can be calculated using the formula D = 47.126v − 1/3. The phases formed during the solidification with lower cooling rates primarily consist of eutectic silicon, M-Mg2Si phase, γ-Al7Cu4Ni phase, δ-Al3CuNi phase, ε-Al3Ni phase, and Q-Al5Cu2Mg8Si6 phase. With the increase in the solidification cooling rate from 0.15 to 15 °C/s, the hardness increased from 80.9 to 125.7 HB, the room temperature tensile strength enhanced from 189.3 to 282.5 MPa, and the elongation at break increased from 1.6% to 2.8%. The ε -Al3Ni phase disappears in the alloy and the Q phase emerges. The δ phase and the γ phase change from large-sized meshes and clusters to smaller meshes and Chinese script patterns. Further increase in the cooling rate leads to the micro hardness increasing gradually from 131.2 to 195.6 HV and the alloy solidifying into a uniform structure and forming nanocrystals.

Investigation on the Case-Hardening Behavior of Additively Manufactured 16MnCr5

“…Thus, high intensities and cooling rates in the order of 10 6 K/s can be observed during the production of parts [4]. These high cooling rates support the formation of a very fine microstructure compared to conventional manufacturing technologies such as, e.g., casting or forging [5,6]. In general, a finer microstructure is preferred to a coarser one, as small grains improve key material properties such as hardness, tensile strength and ductility by suppressing, or at least delaying, crack growth propagation [7].…”

Phase Formation, Microstructure and Mechanical Properties of Mg67Ag33 as Potential Biomaterial

“…% alloy and later successfully employed for estimating the cooling rates inherent to quenching in a water bath [43] or laser powder bed fusion, an additive manufacturing technique [44]. High cooling rates impose kinetic constraints, which can lead to the precipitation of metastable phases whose formation can be favored over the corresponding thermodynamically stable phases [45][46][47]. In the present case, the formation of the γ-Mg 4 Ag phase must have been suppressed, due to rapid cooling.…”

Influence of microwave heating on metallurgical and mechanical properties of Ni-40Cr3C2 composite clads in the context of cavitation erosion resistance characteristics

“…52 However, achieving suitable hardness for a particular material system depends upon the processing conditions. 67,68 Therefore, the hardness value material systems, 25,54,55,65,69,70 similar to the current work material system, were compared for a better understanding of the effect of the processing conditions on hardness. Figure 14 shows the comparison of the hardness of the Cr 3 C 2 reinforced Ni-based composite clads developed by using various cladding methods (laser cladding, PTA welding, and microwave cladding).…”