Formation of Fine Multicomponent Precipitates and Enhanced Precipitation-Hardening in an Al–Cr–Pr–Zr Alloy

The microstructure of the Al­1.0Cr­1.4Pr­1.6Zr (mass%) alloy after homogenized at 500°C for 400h has been investigated. Addition of Cr, Pr and Zr in combination into pure aluminum results in the formation of submicron Zr-containing PrCr2Al20 and nanoscale Cr, Pr-containing Al3Zr dispersed phases. Compared with the Al­1.0Cr­1.4Pr and Al­1.6Zr alloys, a denser distribution of new fine multicomponent dispersed phases and their superimposition effect are associated with enhanced precipitation-hardening behavior of Al­1.0Cr­1.4Pr­1.6Zr alloy. (doi:10.2320/matertrans.M2013149) The alloys with the nominal chemical compositions of Al­1.6Zr, Al­1.0Cr­1.4Pr and Al­1.0Cr­1.4Pr­1.6Zr (all in mass%) were prepared by melting high purity Al (99.9mass%) with Al­Zr, Al­Cr and Al­Pr master alloys using a conventional casting method. The cast ingots were homogenized at 500°C for 400h, and then quenched in water at ambient temperature. The microstructure was observed using an optical microscope. The phase composition was measured by X-ray diffractometry (XRD) in reflection with Cu-Ki radiation. The morphologies and compositions of large intermetallic particles were measured using energy dispersive X-ray spectroscopy (EDS) in a JSM-6360LV scanning electron microscopy (SEM). To investigate the fine precipitates, TEM observation was performed by a TECNAI G 2 20 microscopy and a Jeol JEM-2010F field-emission transmission electron microscopy equipped with a scanning unit. Thin foils for standard TEM observation were prepared by the standard electrolytic twin-jet polishing technique in a7 5% methanol and 25% nitric acid solution cooled down to ³253K with an applied potential of 12­15V and current of 70­90mA. The Brinell hardness was measured with a HRBVU-187.5 hardness tester at a load of 980N.

[1]  Xunhui Xiong,et al.  Precipitates and precipitation behavior in Al–Zr–Yb–Cr alloys , 2012 .

[2]  Kanghua Chen,et al.  A study of nanoscale Al3(Zr,Yb) dispersoids structure and thermal stability in Al–Zr–Yb alloy , 2012 .

[3]  Z. Nie,et al.  Synergetic effect of Er and Zr on the precipitation hardening of Al–Er–Zr alloy , 2011 .

[4]  D. Seidman,et al.  Chemistry and structure of core/double-shell nanoscale precipitates in Al–6.5Li–0.07Sc–0.02Yb (at.%) , 2011 .

[5]  D. Seidman,et al.  Effects of Li additions on precipitation-strengthened Al–Sc and Al–Sc–Yb alloys , 2011 .

[6]  D. Seidman,et al.  Precipitation evolution in Al–0.1Sc, Al–0.1Zr and Al–0.1Sc–0.1Zr (at.%) alloys during isochronal aging , 2010 .

[7]  D. Seidman,et al.  Evolution of nanoscale precipitates in Al microalloyed with Sc and Er , 2009 .

[8]  D. Seidman,et al.  Erbium and ytterbium solubilities and diffusivities in aluminum as determined by nanoscale characterization of precipitates , 2009 .

[9]  D. Seidman,et al.  Precipitation evolution in Al–Zr and Al–Zr–Ti alloys during aging at 450–600 °C , 2008 .

[10]  Lan Huang,et al.  Effect of Yb Additions on Microstructures and Properties of High Strength Al-Zn-Mg-Cu-Zr Alloys , 2007 .

[11]  D. Eskin,et al.  Optimization of hardening of Al–Zr–Sc cast alloys , 2006 .

[12]  Alexis Deschamps,et al.  Complex precipitation pathways in multicomponent alloys , 2006, Nature materials.

[13]  H. Hong,et al.  Microstructural and mechanical properties of nanocrystalline (Al+12.5 at.%Cu)3Zr alloys synthesized by planetary ball milling and spark plasma sintering , 2003 .

[14]  J. Robson,et al.  Predicting recrystallised volume fraction in aluminium alloy 7050 hot rolled plate , 2002 .

[15]  Joseph D. Robson,et al.  Dispersoid precipitation and process modelling in zirconium containing commercial aluminium alloys , 2001 .

[16]  E. Nes.  Precipitation of the metastable cubic Al3Zr-phase in subperitectic Al-Zr alloys , 1972 .

[17]  J. Zhong,et al.  Influence of atomized powder size on microstructures and mechanical properties of rapidly solidified Al–Cr–Y–Zr aluminum alloys , 2008 .