超音波脈衝回波法量測硬脆材料特性之探討

Investigation of Ultrasonic Properties of Brittle Materials

金佩傑(Pei-Chieh Chin) ； 吳士傑(Shih-Jeh Wu) ； 劉杰靈(Hawking Liu)

《高雄師大學報：自然科學與科技類》 38期 (2015/06) Pp. 29-44

摘要

本論文探討硬質材料楊氏係數量測方法，針對ITO玻璃（Alkaline earth boroaluminosilicate）、金屬玻璃（Bulk metallic glass, BMG）及鎳基超合金（CM247LC）三種材料，使用超音波脈衝回波法（pulse-echo）及奈米壓痕（nanoindentation），來作為楊氏系數量測結果的比較。ITO玻璃用超音波量測到的楊氏係數和剪力係數結果，與用奈米壓痕所量測到的結果，差異值分別在0.83%及2.70%之間，顯示超音波量測對均質非晶材料精準度非常好。且超音波用量測縱波及橫波波速，去計算材料浦松比及楊氏係數，對於實際樣品並不會有破壞的行為，而且可在現場量測，既快速又簡便。相對而言，奈米壓痕就有試驗樣品大小上的限制，既無法在現場即時量測，且其量測過程較為緩慢耗時且易受環境干擾。然而在金屬玻璃的結果差異值為23.59%，以及鎳基超合金為5.11%，顯示超音波對量測對象有選擇性，數據必須謹慎處理。金屬玻璃材料成份為金屬與非金屬組合而成，其原子排列方向及熔合金屬和非晶合金之間的界面生成物，對超音波的波速數據有相當的影響，應對其不同的傳遞方向，進行波速的量測與計算。以鎳基的CM247LC超合金金屬材質而言，其晶粒成長方向如樹枝狀（dendrite）結構且具有不同成長方向性，尤其析出carbide碳化及γ-γ'（eutectic phase）相充滿晶界，使得超音波傳播異於一般金屬。

關鍵字

超音波脈衝回波法 ； 奈米壓痕 ； 楊氏系數 ； 金屬玻璃 ； 鎳基超合金

並列摘要

Ultrasonics is an essential part of non-destructive methods of measuring the elastic moduli of materials. Pulse-echo method has been widely used to measure the elastic behavior of materials (elastic moduli and Poisson ratio) along with other destructive methods such as tensile test, compression test and instrumented indentation in industry. However, the commonly used tensile test is not applicable for brittle or tough materials such as glass and ceramics. In this study we performed measurements of acoustic properties on three brittle materials i.e., ITO glass, bulk metallic glass (BMG) and nickel based superalloy (CM247LC). The elastic moduli of materials are derived from the results and they are compared with the data that we obtained with nanoindentation. The difference between the Young's modulus of ITO glass by ultrasonics and nanoindentation is 0.83%, a perfect match within range error. As for BMG the difference (Young's modulus) is 23.59%, and 5.11% for the CM247LC superalloys. The pulse-echo method proves to be reliable for homogeneous amorphous glass; however, the elastic moduli of metallic glass and CM247LC superalloy by ultrasonics are quite different from those by nanoindentation. For both BMG and CM247LC superalloy the ultrasonic pulse-echo method deviates significantly from nanoindentation. The difference is large enough to cover the maximal error associated with the nanoindentation method. The relationship of acoustic speed and elastic constants has to be reviewed in dealing with compound materials.

並列關鍵字

Ultrasonics ； Nano-Indentation ； Young's modulus ； Pulse-echo method ； Intermetallic ； Nickel-based superalloy