Y.W. Riddle’s research while affiliated with Worcester Polytechnic Institute and other places

... In order to understand the role of the microstructure on FCG mechanisms, the unique microstructure of this alloy must first be discussed. It has been established in the literature (Shankar et al. [27,28]) that Sr additions significantly alter the solidification behavior in this alloy system, and will be described briefly here as its effects relate to the mechanisms of FCG. During solidification, primary a-Al dendrites will be the first phase to solidify. ...

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Microstructural Mechanisms and Advanced Characterization of Long and Small Fatigue Crack Growth in Cast A356-T6 Aluminum Alloys

... However, some studies [25][26][27][28] revealed how these impurities can be quite effective during the formation of Al-Si eutectic structure. According to Shankar et al. [29], the precipitation of primary ␣-Al from the liquid phase is followed by the formation of secondary ␤-Al 5 FeSi phase at temperature above the eutectic point. The eutectic Si can nucleate on the ␤-Al 5 FeSi phase before the eutectic ␣-Al nucleation on the Si particle. ...

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Lanthanides: A focused review of eutectic modification in hypoeutectic Al–Si alloys

... This alloy has a thermally stable microstructure consisting of an a-Mg matrix, Mg eutectics, and various primary and secondary phases containing rare earth elements [42]. The ZE41A Mg cast alloy used in this study was heat treated to the T-5 condition, which is an artificially aged condition and the microstructure consists of a-Mg and b-Mg-Zn-RE according to Riddle et al. [43]. Figure 11 shows the b-Mg-Zn-RE grain boundary phase. ...

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Dissimilar Metal Joining and Structural Repair of ZE41A-T5 Cast Magnesium by the Cold Spray (CS) Process

... Since the mid-1980s, there has been a strong interest in the addition of scandium to zirconium as solutes in aluminium [1,2]. It was shown that such an addition resulted in a significant enhancement of the resistance to recrystallization, and consequently in better mechanical properties [3][4][5][6][7][8][9][10]. Scandium also forms L1 2 Al 3 Sc precipitates with aluminium, which is in this case the stable phase [11][12][13][14][15][16]. ...

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In situ small-angle scattering study of the precipitation kinetics in an Al–Zr–Sc alloy

... The critical P content for Al-Si alloys to precipitate AlP before (Si) has been determined through meticulous thermodynamic calculations [7]. On the other hand, Shankar et al. [8,9] proposed the assumption that β-(Al,Si,Fe) initiates the nucleation event of eutectic (Si), and insisted on that assumption [10,11] after the argument with Dahle and Hillert [12,13]. In the present work, we shall reexamine the assumption on β-(Al,Fe,Si) and clarify the dispute by dedicated thermodynamic calculations. ...

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Nucleants of Eutectic Silicon in Al-Si Hypoeutectic Alloys: beta-(Al, Fe, Si) or AlP Phase

... Based on Refs. [10][11][12], Zr addition will lead to the formation of fine spherical and coherent Al 3 Zr particles with a tetragonal lattice, which plays an essential role in pinning dislocation and boundary mobility during hot rolling and recrystallization. Actually, from the aspect of plastic deformation, rolling texture formation is essentially achieved in a way of dislocation movement, and thereby Al 3 Zr phase will definitely affect the formation of deformation texture. ...

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Enhanced Brass texture of hot-rolled Al-4Cu-1.6Mg alloy by 0.1% Zr addition

... Under the fastest ramp (i.e., R3), however, the Al 3 (Sc,Zr) precipitates appear with the smallest size and the highest aerial number density in all of the heating ramps. The precipitation of Al 3 (Sc,Zr) precipitates has been proven to effectively prohibit the migration of dislocations and grain boundaries and subsequently mitigate recrystallization [49,50]. In a study by Jones and Humphreys [49] on the interaction of recrystallization and precipitation, it was observed that the precipitation of Al 3 Sc precipitates always precedes recrystallization in an Al-0.25 wt.%Sc alloy at temperatures below 500°C. ...

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Precipitation-induced mitigation of recrystallization in ultra-thin, cold-rolled AlScZrMn(Mg) sheets at brazing temperatures: The critical effect of alloy composition and thermal processing route

... Both α-Al (Mn,Fe) Si and Al 3 Zr exhibit good heat resistance, according to the results in Figure 8. These nano-scale particles could significantly inhibit the occurrence of recrystallization nucleation by exerting strong pinning effects on the movements of dislocations and grain boundaries during high-temperature recovery and recrystallization [26,[29][30][31]. The coarse Al 6 (Mn,Fe) phases in the alloy also have very high thermal stability, and could serve as recrystallization cores for nucleation due to their large size [12,28,32]. ...

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High-Temperature Mechanical Properties and Microstructure of Ultrathin 3003mod Aluminum Alloy Fins

... This is due to the small latent heat release from Al-Mn-(Fe) intermetallics as the phase fractions are very small (each is less than 0.2 mass % [32]). To compare the development of solid fraction on cooling with the calculations in Fig. 1(e), Newtonian cooling curve analysis was performed on the cooling curve data in Fig. 1(h) using the approach widely adopted in past work [38e40] and the data for the specific heat capacity and latent heat of a-Mg and Mg 17 Al 12 from Ref. [40]. ...

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Nucleation and growth crystallography of Al8Mn5 on B2-Al(Mn,Fe) in AZ91 magnesium alloys

... Terefore, monitoring the concentrations of micro-or trace elements in aluminum alloys is essential for quality control of aluminum alloys production or industrial products produced with them. Traditional concentration measurement methods for elements in aluminum alloys include chemical analysis [1][2][3] and inductively coupled plasma atomic emission spectrometry (ICP-AES) [4]. Although these methods show low detection limits and high measurement accuracy, they require complex chemical treatment for samples, which is time-consuming and not convenient or efcient for on-site practical applications. ...

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One-Point and Multiline Calibration Fiber-Optic Laser-Ablation Spark-Induced Breakdown Spectroscopy for Quantitative Analysis of Elements in Aluminum Alloys