Empirical mapping of ZrCu-based alloys with valence electrons versus transformation temperatures

Abstract

under compressive loading because the B2-structured nanocrystals undergo a martensitic transformation during deformation [7,8]. Therefore, it is necessary to design the chemical composition of such materials to control the martensitic transformation temperatures, in order to acquire high transformation temperatures in HTSMA devices or to obtain B2 phase-BMG composites for applied use [9,10].The mechanism that allows alloying elements to change their transformation temperatures is dependent upon the electronic structures and the interatomic bonding forces within such alloys [11]. The valence electrons contributed by s + d electrons of the transition metals, or s + p electrons of the non-transition metals, act as adhesives during metallic bonding [12,13]. The strength of this adhesion, which depends on the number (e v /a), concentration (c v ), density (n) of valence electrons, is relevant to the transformation temperatures of SMAs [11][12][13][14][15][16]. For ZrCu-based alloys, the relationship between transformation temperature and electronic structure has yet to be quantified, and therefore a guiding empirical map is necessary to design and optimize the central properties in ZrCu-based alloys. In this paper, we have examined the number (e v /a), concentration (c v ) and density (n) of valence electrons as correlates with the transformation temperatures of various ZrCu-based alloys. Understanding such correlations would significantly benefit the design of ZrCu-based alloys for different application backgrounds. MATERIALS AND EXPERIMENTAL PROCEDURETo adjust the Zr/Cu ratio through substitutions of Zr or Cu with Hf, Co, Ti, Ag, Ni, Al or Cr, ZrCu-based alloys were melted using high-purity metals in a non-consumed vacuum arc furnace under Ar. The ingots were then melted six more times to ensure compositional homogeneity (turning the button 180° for each repetition). The samples were annealed in vacuum quartz tubes at 1073 K for

Effect of Sn Content on the Microstructural Features, Martensitic Transformation and Mechanical Properties in Ti-V-Al-Based Shape Memory Alloys

“…reversely leads to the reduction of A s . In addition, the effect of alloying elements on the martensitic transformation temperatures of shape memory alloys is also largely dependent on the e/a and concentration of valence electrons (C v ) [40,41]. Meanwhile, the relationship among e/a, C v and A s of the reported Ti-V-Al-based shape memory alloys is plotted in Fig.…”