| 摘要: | 本研究藉由攪拌鑄造法，熔配含微量鈣( x = 0、0.1、0.3, wt%)之三種合金Mg-4.6Sn-2.4Zn-0.07Na (TZS420)、Mg-4.6Sn-2.4Zn-0.07Na-0.1Ca (TZS420-0.1Ca)、Mg-4.6Sn-2.4Zn-0.07Na-0.3Ca (TZS420-0.3Ca)，探討微量鈣對合金微結構、電化學性質、機械性質、生物特性等之影響。
結果顯示，鈣含量愈高，鑄造合金之硬度、腐蝕電位、腐蝕速率愈高，
而隨鈣含量的增加，鑄造合金之微結構以及生物相容性呈現顯著變化，TZS420微結構為α-Mg枝狀晶和板狀富錫相、顆粒狀共晶Mg2Sn相、Sn-Na共同富集區。
TZS420-0.1Ca合金之微結構為α-Mg枝狀晶、針狀二次相、顆粒狀Mg2Sn相、顆粒狀富鋅相以及條狀二次相，TZS420-0.3Ca出現α-Mg枝狀晶、板狀共晶Mg2Sn相以及顆粒狀富鋅相、針狀CaMgSn介金屬相。
透過添加鈣進行改質，可有效細化晶粒尺寸，TZS420平均晶粒尺寸為313.1 μm，TZS420-0.1Ca為168.1 μm而TZS420-0.3Ca為152.2 μm使硬度顯著提升分別為HV 107、HV 119 ，且透過細晶強化TZS420-0.1Ca之UTS為三組合金中最佳高達131.2 MPa。此外，添加微量鈣可將腐蝕形貌從嚴重局部腐蝕轉變成孔蝕，然而因第二相之體積分率隨鈣含量的添加而上升，造成腐蝕速率顯著上升。
而TZS420-0.1Ca合金之生物相容性最佳(細胞存活率高達90 %)，TZS420-0.3Ca次之(細胞存活率約81~82%)，TZS420最差(細胞存活率約50%)，原因為鈣離子有促進細胞分化之效用使細胞存活率上升，且CT掃瞄圖顯示TZS420-0.1Ca在植入時間為13週時並未被完全降解且從組織染色切片結果顯示，植入時間為13週時TZS420-0.1Ca周圍出現大量膠原蛋白，顯示其具有促進骨修復之潛在可能性。
;In this study, three magnesium alloys containing trace amounts of calcium (x = 0, 0.1, 0.3 wt%)—namely Mg-4.6Sn-2.4Zn-0.07Na (TZS420), Mg-4.6Sn-2.4Zn-0.07Na-0.1Ca (TZS420-0.1Ca), and Mg-4.6Sn-2.4Zn-0.07Na-0.3Ca (TZS420-0.3Ca)—were fabricated via stir casting to investigate the effects of calcium addition on their microstructure, electrochemical properties, mechanical properties, and biocompatibility.
The results showed that increasing calcium content led to higher hardness, corrosion potential, and corrosion rate of the as-cast alloys. The microstructure and biocompatibility also changed significantly with calcium content. The TZS420 alloy exhibited an α-Mg dendritic structure, lamellar Sn-rich phase, granular eutectic Mg₂Sn phase, and Sn-Na co-enrichment regions. The TZS420-0.1Ca alloy displayed α-Mg dendrites, needle-like secondary phases, granular Mg₂Sn, Zn-rich phases, and strip-like secondary phases. In TZS420-0.3Ca, α-Mg dendrites, lamellar eutectic Mg₂Sn, granular Zn-rich phases, and needle-like CaMgSn intermetallic compounds were observed.
Calcium addition refined the grain size effectively: the average grain size decreased from 313.1 μm (TZS420) to 168.1 μm (TZS420-0.1Ca) and 152.2 μm (TZS420-0.3Ca), resulting in a significant increase in hardness to HV 107 and HV 119, respectively. The TZS420-0.1Ca alloy exhibited the highest ultimate tensile strength (UTS) among the three, reaching 131.2 MPa due to grain refinement strengthening. Moreover, the corrosion morphology changed from severe localized corrosion to pitting corrosion upon calcium addition. However, the increasing volume fraction of second phases with calcium content led to a significant rise in corrosion rate.
In terms of biocompatibility, TZS420-0.1Ca showed the best performance (cell viability up to 90%), followed by TZS420-0.3Ca (about 81–82%), and TZS420 showed the lowest (around 50%). This improvement is attributed to calcium ions promoting cell differentiation. CT scans indicated that TZS420-0.1Ca was not fully degraded after 13 weeks of implantation. Histological staining also revealed abundant collagen surrounding the TZS420-0.1Ca implant at 13 weeks, indicating its potential for promoting bone regeneration. |
